Chest Imaging

Segmental Anatomy ( Figs. 1.1 – 1.2 )

Segmental Computed Tomography (CT) Anatomy ( Fig. 1.3 )

Bronchial CT Anatomy ( Fig. 1.4 )

Plain Radiograph Anatomic Landmarks ( Figs. 1.5–1.9 )

Upper Lobe (Ul) Bronchi ( Figs. 1.10 – 1.11 )

The right main bronchus divides into the RUL bronchus and the bronchus intermedius.

• RUL bronchus is always higher than LUL bronchus on lateral view

• Posterior wall of bronchus intermedius (right) is normally less than 2 mm thick and bifurcates into middle and LLs bronchi

• Tracheal bronchus (bronchus suis): 0.1% of population, arises from right wall of trachea (left much less common), supplies apical segment or occasionally entire RUL

• The left main bronchus is approximately 5 cm in length and divides into the LUL and LLL bronchi.

• Accessory cardiac bronchus: 0.1% of population, extends inferomedially from medial wall of bronchus intermedius or RLL bronchus toward mediastinum; may be blind ending

Acinus

• Includes all structures distal to one terminal bronchiole. The terminal bronchiole is the last purely air-conducting structure.

• Acinus measures 7 mm

• Acinus contains about 400 alveoli

Secondary Pulmonary Lobule

• Smallest anatomic unit of the lung visible on high-resolution CT (HRCT)

• Polygonal structure bounded by interlobular septa, 1.5–2 cm in diameter

• Three to five acini per secondary lobule

• Supplied by several terminal bronchioles

Epithelium

• The alveolar epithelium is made up of two cell types:

  • Type 1 pneumocytes

  • Type 2 pneumocytes: produce surfactant, have phagocytic ability, and regenerate

High-Resolution Computed Tomography (HRCT) ( Fig. 1.12 )

Lung Volumes, Capacities, and Flow Rates

• Tidal volume (TV): normal respiratory cycle

• Vital capacity (VC): amount of air that can be expired with force after maximal inspiration

• Functional residual capacity (FRC): volume remaining in lung after quiet expiration

• Total lung capacity (TLC): volume contained in lung at maximum inspiration

• Forced expiratory volume (FEV ₁ ): amount of air expired in 1 second

Standard Chest CT Protocol

Supine position. Scan in suspended inspiration at total lung capacity. Scan setup:

• 5 × 5-mm sections from apex of the lungs to the adrenals

• Six 1.25-mm high-resolution cuts throughout lung at 2.5-cm intervals

• 1-mm reconstructions through pulmonary nodules

• Number of different combinations of pitch and section thickness

In interstitial lung disease the six cuts are repeated with the patient in the prone position. Reconstruction is done with a high-resolution bone algorithm.

Use of IV contrast medium:

• Evaluation of vascular structures, arteriovenous malformation, aortic dissection

• Evaluation of mediastinal tumors, enlarged lymph nodes

• Hilar masses

• Neck masses

Pulmonary Embolism (PE) CT Protocol

• Patient in supine position

• Scan range: adrenals to lung apex

• Injection of 140 mL of nonionic iodinated contrast at 3 mL/second, with delay of 25–30 seconds. Scanning is performed with suspended respiration.

• Scans are retrospectively reconstructed from the dome of the diaphragm as 2.5-mm-thick slices with 1-mm spacing.

Diagnostic Radiology Report (American College of Radiology [ACR])

An authenticated written interpretation should be performed on all radiologic procedures. The report should include:

• 1

  Name of patient and other identifier (e.g., birth date, Social Security number, or hospital or office identification number)

• 2

  Name of the referring physician to provide more accurate routing of the report to one or more locations specified by the referring physician (e.g., hospital, office, clinic)

• 3

  History

• 4

  Name or type of examination

• 5

  Dates of the examination and transcription

• 6

  Time of the examination (for ICU/CCU patients) to identify multiple examinations (e.g., chest) that may be performed on a single day

• 7

  Body of the report:

  • Procedures and materials

    • Include in the report a description of the procedures performed and any contrast media (agent, concentration, volume, and reaction, if any), medications, catheters, and devices.

  • Findings

    • Use precise anatomic and radiologic terminology to accurately describe findings.

  • Limitations

    • Where appropriate, identify factors that can limit the sensitivity and specificity of the examination. Such factors might include technical factors, patient anatomy, limitations of the technique, incomplete bowel preparation, and wrist examination for carpal scaphoid.

  • Clinical issues

    • The report should address or answer any pertinent clinical issues raised in the request for the imaging examination. For example, to rule out pneumothorax state: “There is no evidence of pneumothorax.” To rule out fracture state: “There is no evidence of fracture.” It is not advisable to use such universal disclaimers as “The mammography examination does not exclude the possibility of cancer.”

  • Comparative data

    • Comparisons with previous examinations and reports when possible are a part of the radiologic consultation and report and optionally may be part of the “impression” section.

• 8

  Impression (conclusion or diagnosis):

  • Each examination should contain an “impression” section.

  • Give a precise diagnosis whenever possible.

  • Give a differential diagnosis when appropriate.

  • Recommend, only when appropriate, follow-up and additional diagnostic radiologic studies to clarify or confirm the impression.

    • In normal CXR section the only structures visible in normal lungs are the fissures and the pulmonary vessels.

    • Lung parenchymal abnormalities are divided into five basic patterns:

      • 1

        Mass

      • 2

        Consolidative

      • 3

        Interstitial

      • 4

        Vascular

      • 5

        Airway

Pathogens

• Bacterial pneumonia

  • Streptococcus pneumoniae (pneumococcus)

  • Staphylococcus

  • Pseudomonas

  • Klebsiella

  • Nocardia

  • Chlamydia

  • Neisseria meningitides

  • Haemophilus influenzae

  • Anaerobes

  • Legionella

  • Mycoplasma pneumoniae

  • Actinomyces israelii

  • Mycobacterium tuberculosis

• Viral pneumonia (25% of community-acquired pneumonias)

  • Influenza

  • Varicella, herpes zoster

  • Rubeola

  • Cytomegalovirus

  • Coxsackievirus, parainfluenza virus, adenovirus, respiratory syncytial virus (RSV)

• Fungal pneumonia

  • Histoplasmosis

  • Coccidioidomycosis

  • Blastomycosis

  • Aspergillosis

  • Cryptococcosis

  • Candidiasis

  • Zygomycoses

• Parasitic pneumonias

  • Pneumocystis jiroveci Frenkel 1999 (formerly Pneumocystis carinii )

  • Toxoplasma gondii

Acquisition of Pneumonia

• Community-acquired pneumonia

  • S. pneumoniae , Haemophilus

  • Mycoplasma

• Hospital-acquired pneumonia (incidence 1%, mortality 35%): nosocomial infection

  • Gram-negative bacteria: Pseudomonas , Proteus , Escherichia coli , Enterobacter , Klebsiella

  • Methicillin-resistant Staphylococcus aureus (MRSA)

  • Vancomycin-resistant enterococcus (VRE)

• Pneumonia in immunosuppressed patients

  • Bacterial pneumonia (gram negative) still most common

  • Tuberculosis

  • Fungal

  • Pneumocystis pneumonia (PCP)

• Endemic pneumonias

  • Fungal: histoplasmosis, coccidioidomycosis, blastomycosis

  • Viral

• Aspiration-associated pneumonia (important)

Risk Factors

The radiographic appearance of pulmonary infections is variable depending on the pathogen, underlying lung disease, risk factors, and previous or partial treatment.

• Other risk factors for developing pneumonia:

  • Bronchiectasis

  • Coma, anesthesia, seizures (aspiration)

  • Tracheotomy

  • Antibiotic treatment

  • Immunosuppression (renal failure, diabetes, cancer, steroids, AIDS)

  • Chronic furunculosis ( Staphylococcus )

Radiographic Spectrum of Pulmonary Infections

SUMMARY

Type	Pathogen	Imaging
Lobar Pneumonia
Infection primarily involves alveoli Spread through pores of Kohn and canals of Lambert throughout a segment and ultimately an entire lobe Bronchi are not primarily affected and remain air filled; therefore: Air bronchograms No volume loss because airways are open	Streptococcus pneumoniae Klebsiella pneumoniae Others Staphylococcus aureus Haemophilus influenzae Fungal
Nowadays uncommon because of early treatment Round pneumonia (more common in children)
Bronchopneumonia
Primarily affects the bronchi and adjacent alveoli Volume loss may be present as bronchi filled with exudates Bronchial spread results in multifocal patchy opacities	S. aureus Gram-negative bacteria Others H. influenzae Mycoplasma
Nodules
Variable in size Indistinct margins	Fungal Histoplasma Aspergillus Cryptococcus Coccidioides Bacterial Legionella Nocardia Septic emboli S. aureus
Cavitary Lesions (Infectious)
Abscess: necrosis of lung parenchyma ± bronchial communication Fungus ball (air crescent/monad sign) Postprimary TB (favor apical and posterior segments of the upper lobes) Pneumatoceles caused by air leak into pulmonary interstitium	Anaerobic bacteria Aspergillus M. tuberculosis S. aureus
Diffuse Opacities
Reticulonodular pattern: interstitial peribronchial areas of inflammation (viral) Alveolar location (PCP) Miliary pattern: hematogenous spread (TB)	Viral Mycoplasma PCP

PCP , Pneumocystis pneumonia; TB , tuberculosis.

Resolution of Pneumonia

• 80%–90% of cases resolve within 4 weeks.

• 5%–10% resolve within 4–8 weeks (usually in older or diabetic patients). Subsequent radiographs should always show interval improvement compared with the previous radiographs.

• Nonclearance

  • Antibiotic resistance

  • Consider other pathogen (e.g., M. tuberculosis )

  • Recurrent infection

  • Obstruction pneumonitis due to tumor

General

Streptococcal Pneumonia

Staphylococcal Pneumonia ( Fig. 1.15 )

Pseudomonas Pneumonia

Legionnaires Disease

Severe pulmonary infection caused by Legionella pneumophila; 35% of patients require ventilation, 20% mortality. Most infections are community acquired. Patients have hyponatremia. Seroconversion for diagnosis takes 2 weeks.

Haemophilus Pneumonia

Caused by H. influenzae . Occurs most commonly in children, immunocompromised adults, or patients with COPD. Often there is concomitant meningitis, epiglottitis, and bronchitis.

Mycoplasma Pneumonia

Most common nonbacterial pneumonia (atypical pneumonia). Mild course. Age 5–20 years. Positive for cold agglutinins, 60%.

Klebsiella (Friedländer) Pneumonia

Gram-negative organism. Often in debilitated patients and/or alcoholics.

Tuberculosis (TB) ( Fig. 1.16 )

Transmitted by inhalation of infected droplets of M. tuberculosis or M. bovis . TB acquisition usually requires constant or repeated contact with sputum-positive patients because the tubercle does not easily grow in the immunocompetent human host. Target population includes:

• Patients of low socioeconomic status (homeless)

• Alcoholics

• Immigrants: from Mexico, Philippines, Indochina, Haiti

• Elderly patients

• AIDS patients

• Prisoners

Primary Infection ( Fig. 1.17 )

Usually heals without complications. Sequence of events includes:

• Pulmonary consolidation (1–7 cm); cavitation is rare; LL (60%) > UL

• Caseous necrosis 2–10 weeks after infection

• Lymphadenopathy (hilar and paratracheal), 95%

• Pleural effusion, 10%

• Spread of a primary focus occurs primarily in children or immunosuppressed patients.

Secondary Infection ( Fig. 1.18 )

Active disease in adults most commonly represents reactivation of a primary focus. However, primary disease is now also common in adults in developed countries because there is no exposure in childhood. Distribution is as follows:

• Typically limited to apical and posterior segments of ULs or superior segments of LLs (because of high P o ₂ ?)

• Rarely in anterior segments of ULs (in contradistinction to histoplasmosis)

Complications ( Fig. 1.19 )

• Miliary TB may occur after primary or secondary hematogenous spread.

• Bronchogenic spread occurs after communication of the necrotic area with a bronchus; it produces an acinar pattern (irregular nodules approximately 5 mm in diameter).

• Tuberculoma (1–7 cm): nodule during primary or secondary TB; may contain calcification

• Effusions are often loculated.

• Bronchopleural fistula

• Pneumothorax

COMPARISON

	Primary TB	Reinfection TB
Location	Usually bases	Upper lobes, superior segment
		Lower lobes
Appearance	Focal	Patchy
Cavitation	No	Frequent
Adenopathy as only finding	Common	No
Effusion	Common	Uncommon
Miliary pattern	Yes	Yes

TB , Tuberculosis.

Nontuberculous Mycobacterial (NTMB) Infections

The two most common NTMB pathogens are M. avium-intracellulare and M. kansasii (less common: M. xenopi , M. chelonei , M. gordonae, M. fortuitum , “fast grower”). Unlike TB, NTMB infections are not acquired by human-human transmission but are a direct infection from soil or water. There is also no pattern of primary disease or reactivation: the infection is primary, although some infections may become chronic. The infection often occurs in elderly patients with COPD, older women in good health, and AIDS patients.

Nocardia Pneumonia

Caused by Nocardia asteroides , worldwide distribution. Common opportunistic invader in:

• Lymphoma

• Steroid therapy; especially transplant patients

• Pulmonary alveolar proteinosis (common)

Actinomycosis

Actinomycosis is caused by Actinomyces israelii, a gram-positive normal saprophyte in the oral cavity. Pulmonary disease develops from aspiration of the organism (poor dentition) or from direct penetration into the thorax.

Pulmonary Abscess

The spectrum of anaerobic pulmonary infections includes:

• Abscess: single or multiple cavities >2 cm, usually with AFL

• Necrotizing pneumonia: analogous to abscess but more diffuse and cavities <2 cm

• Empyema: suppurative infection of the pleural space, most commonly as a result of pneumonia

Sickle Cell Anemia

• Patients with sickle cell disease are at increased risk of pneumonia and infarction. These entities are difficult to differentiate, and hence are called acute chest syndrome .

• Pneumonias were originally due to pneumococci but now are due to viruses or Mycoplasma. Differential diagnosis includes atelectasis and infarct.

• Infarcts are more frequent in adults than in children. Rare in children younger than 12 years.

• Consolidation is seen on CXRs; resolves more slowly than in the general population and tends to recur.

General

Influenza Pneumonia

Influenza is very contagious and thus occurs in epidemics. Pneumonia, however, is uncommon.

Involves the upper respiratory tract, including the trachea and major bronchi.

Varicella-Zoster Pneumonia

Fifteen percent of infected patients have pneumonias; 90% are older than 20 years.

Measles Virus Pneumonia

• Two forms:

  • Primary measles virus pneumonia and secondary bacterial pneumonia

  • Atypical measles virus pneumonia

Cytomegalovirus (CMV) Pneumonia

Occurs most commonly in neonates or immunosuppressed patients.

Swine-Origin Influenza a (H1N1) Virus Infection

Epidemiologic data to date suggest that the newly emerged H1N1 virus, although transmissible from person to person, is of relatively low virulence. CXRs are normal in more than half of patients. However, the disease can progress to bilateral extensive ASD in severely ill patients. These patients are also at high risk of PE, which should be sought carefully on contrast-enhanced CT scans.

Severe Acute Respiratory Syndrome

Emerging highly contagious infection caused by a coronavirus; first outbreak reported in southern China in 2002. The disease has two clinical stages: viral replicative stage and immunopathologic stage. The incubation period for the virus ranges from 2 to 12 days.

General

Two broad categories:

• Endemic human mycoses (prevalent only in certain geographic areas):

  • Histoplasmosis (Ohio, Mississippi, St. Lawrence river valleys)

  • Coccidioidomycosis (San Joaquin Valley)

  • Blastomycosis

Opportunistic mycoses (worldwide in distribution) occur primarily in immunocompromised patients (aspergillosis and cryptococcosis may also occur in immunocompetent hosts):

• Aspergillosis

• Candidiasis

• Cryptococcosis

• Mucormycosis

Histoplasmosis ( Fig. 1.20 ): Pulmonary and Mediastinal

Histoplasma capsulatum is particularly prevalent in the Ohio, Mississippi, and St. Lawrence river valleys, although the agent has a worldwide distribution. The organism is most prevalent in soil that contains excrement of bats and birds (bat caves, chicken houses, old attics, or buildings).

Coccidioidomycosis ( Fig. 1.21 )

Coccidioides immitis is endemic in the southwest United States (San Joaquin Valley, “valley fever”) and in Central America and South America. Infection occurs by inhalation of spores in soil. Human-to-human infection does not occur.

North American Blastomycosis ( Fig. 1.22 )

• Caused by Blastomyces dermatitidis ; uncommon infection. Most infections are self-limited.

• CXR is nonspecific: ASD > nodule (15% cavitate) or solitary mass > miliary spread.

• Focal or diffuse air space consolidation is the most common radiologic finding.

• Focal blastomycosis typically occurs in paramediastinal location and has an air bronchogram, findings that may suggest the diagnosis.

• Satellite nodules around primary focus are common.

• Chronic blastomycosis may mimic lung cancer because it can manifest itself as a focal mass. An air bronchogram or presence of satellite nodules is suggestive of correct diagnosis.

• Adenopathy, pleural effusions, and calcifications are very uncommon.

• Bone lesions, 25%

• Skin lesions are common.

Aspergillosis ( Fig. 1.23 )

Aspergillus is a ubiquitous fungus that, when inhaled, leads to significant lung damage. The fungus grows in soil, water, decaying vegetation, and hospital air vents. Infection with A. fumigatus > A. flavus , A. niger , or A. glaucus. There are four unique forms of pulmonary aspergillosis, each associated with a specific immune status.

Allergic Bronchopulmonary Aspergillosis (ABPA)

ABPA is a complex type I (IgE-mediated) and type III (IgG-mediated) hypersensitivity reaction to A. fumigatus, occurring primarily in individuals with asthma and occasionally in individuals with cystic fibrosis. The hypersensitivity initially causes bronchospasm, mucus production, and bronchial wall edema (IgE mediated); ultimately there is bronchial wall damage due to the type III IgG-mediated response, with resultant cystic bronchiectasis.

Aspergilloma (Mycetoma, Fungus Ball)

This is a saprophytic infection that occurs in the setting of structural lung disease (from TB, sarcoid, emphysema). Commonly in ULs, solitary lesions. The fungus grows into the preexisting cavity (e.g., cyst, bulla, bronchiectasis), creating a “fungus ball” consisting of fungus, mucus, and inflammatory cells. Individuals with mycetomas are often asymptomatic but may develop recurrent hemoptysis, which in rare cases can be massive. In these cases, bronchial artery embolization is indicated. The other treatment options include surgical resection, intracavity administration of amphotericin B, and systemic antifungal therapy.

Invasive Aspergillosis

Invasive aspergillosis has a high mortality rate (70%–90%) and occurs mainly in severely immunocompromised patients (bone marrow transplants, leukemia). The infection starts with endobronchial fungal proliferation and then leads to vascular invasion with thrombosis and infarction of the lung (“angioinvasive infection”). Additional sites of infection (in 30%) are the brain, liver, kidney, and GI tract. Treatment is with systemic and/or intracavitary administration of amphotericin.

Radiographic Features ( Fig. 1.25 )

• Multiple pulmonary nodules, 40%

• Nodules have a characteristic halo of ground-glass appearance (represents pulmonary hemorrhage)

• Within 2 weeks, 50% of nodules undergo cavitation, which results in the air crescent sign. The appearance of the air crescent sign indicates the recovery phase (increased granulocytic response). The air crescent sign may also be seen in TB, actinomycosis, mucormycosis, septic emboli, and tumors. Do not confuse the air crescent sign with the Monod sign (clinical history helps to differentiate the two).

• Other manifestations:

  • Peribronchial opacities

  • Focal areas of consolidation

Semiinvasive Aspergillosis

This form of aspergillosis occurs in mildly immunocompromised patients and has a pathophysiology similar to that of invasive aspergillosis except that the disease progresses more chronically over months (mortality rate 30%). Risk factors include diabetes, alcoholism, pneumoconiosis, malnutrition, and COPD. Treatment is with systemic and/or intracavitary administration of amphotericin.

Cryptococcosis

Caused by Cryptococcus neoformans , which has a worldwide distribution and is ubiquitous in soil and pigeon excreta. Infection occurs through inhalation of contaminated dust.

Candidiasis

Caused by Candida albicans more frequently than other Candida species.

Zygomycoses

Group of severe opportunistic mycoses caused by fungi of the Zygomycetes class:

• Mucormycosis ( Mucor )

• Rhizopus

• Absidia

Zygomycoses usually have two major clinical manifestations:

• Pulmonary mucormycosis

• Rhinocerebral mucormycosis

Zygomycoses are uncommon infections and occur primarily in immunocompromised patients (leukemia, AIDS, chronic steroid use, diabetes).

Clinical Findings

• Lymphadenopathy

• Opportunistic infections

• Tumors: lymphoma—usually B-cell non-Hodgkin's lymphoma (NHL), Kaposi sarcoma (KS)

• Other manifestations:

  • Associated with lymphocytic interstitial pneumonia (LIP), usually in childhood

  • Spontaneous pneumothorax (development of cystic spaces, interstitial fibrosis related to PCP)

  • Septic emboli

• Clinical findings supportive of AIDS diagnosis ( Fig. 1.26 ):

  • CD4 cell count <200/mm ³ ; the dysfunction of the immune system is inversely related to the CD4 cell count; PCP, CD4 cell count <200/mm ³ ; MAI infection, CD4 cell count <50/mm ³

  • Less than one case of bacterial pneumonia per year

  

General

• 50% of all AIDS patients have pulmonary manifestations of infection or tumor.

• A normal CXR does not exclude the diagnosis of PCP.

• CMV infection is common at autopsy but does not cause significant morbidity or death; CMV antibody titers are present in virtually all patients with AIDS.

• Use of chest CT in AIDS patients:

  • Symptomatic patient with normal CXR; however, patients will commonly first undergo induced sputum or bronchoscopy or be given empirical therapy for PCP.

  • To clarify confusing CXR findings

  • Workup of focal opacities, adenopathy, nodules

Spectrum of Chest Manifestations ( Fig. 1.27 )

• Nodules

  • KS (usually associated with skin lesions)

  • Septic infarcts (rapid size increase)

  • Fungal: Cryptococcus , Aspergillus

• Large opacity: consolidation, mass

  • Hemorrhage

  • NHL

  • Pneumonia

  • Linear or interstitial opacities

  • PCP

  • Atypical mycobacteria

  • KS

• Lymphadenopathy

  • Mycobacterial infections

  • KS

  • Lymphoma

  • Reactive hyperplasia, rare in thorax

• Pleural effusion

  • KS

  • Mycobacterial, fungal infection

  • Pyogenic empyema

Mycobacterial Infection

M. tuberculosis > M. avium-intracellulare (MAI) (this pathogen usually causes extrathoracic disease). CD4 cell count usually <50/mm ³ .

Fungal Infections

Fungal infections in AIDS are uncommon (<5% of patients):

• Cryptococcosis (most common); 90% have CNS involvement.

• Histoplasmosis: nodular or miliary pattern most common; 35% have a normal CXR.

• Coccidioidomycosis: diffuse interstitial pattern, thin-walled cavities

Kaposi Sarcoma (KS) ( Fig. 1.31 )

The most common tumors in AIDS are:

• KS (15% of patients); incidence declining; male-female ratio 50 : 1

• Lymphoma (<5% of patients)

Pulmonary manifestations of KS (almost always preceded by cutaneous/visceral involvement):

• Nodules

  • 1–3 cm

  • Spiculated “flame-shaped” nodules with peribronchovascular distribution in advanced disease

• Coarse reticular opacities emanating from hilum

• Pleural effusions (serosanguineous), 40%

• Adenopathy

• Lymphangitic tumor spread

AIDS-Related Lymphoma

NHL (usually aggressive B-cell type) > Hodgkin lymphoma.

Poor prognosis. The spectrum includes:

• Solitary or multiple pulmonary masses with or without air bronchogram, 25%

• AIDS-related lymphoma is typically an extranodal disease (CNS, GI tract, liver, bone marrow): adenopathy not very prominent.

• Pleural effusions are common.

Location

Chest neoplasms are best categorized by their primary location:

• Lung tumors

• Pleural tumors

• Mediastinal tumors

• Tumors of the airway

• Chest wall tumors

Classification of Pulmonary Neoplasm

• Malignant tumors

  • Bronchogenic carcinoma

  • Lymphoma

  • Metastases

  • Sarcomas, rare

• Low-grade malignancies (previously bronchial adenoma)

  • Carcinoid, 90%

  • Adenoid cystic carcinoma (previously cylindroma, resembles salivary gland tumor), 6%

  • Mucoepidermoid carcinoma, 3%

  • Pleomorphic carcinoma, 1%

• Benign tumors, rare

  • Hamartoma

  • Papilloma

  • Leiomyoma

  • Hemangioma

  • Chemodectoma

  • Pulmonary blastoma

  • Chondroma

  • Multiple pulmonary fibroleiomyomas

  • Pseudolymphoma

Lung Cancer Screening

• Low-dose chest CT

• Uses the Lung-RADS assessment to categorize patients, which can be accessed at https://www.acr.org/Quality-Safety/Resources/LungRADS .

• Lung-RADS stratifies patients on the basis of presence, size, and morphology of pulmonary nodules into different follow-up and management categories.

• Patients qualify if they are between 55 and 74 years old with at least a 30-pack-year smoking history.

• Yearly CT screening decreased lung cancer mortality in this subset of patients by 20% and all-cause mortality by 6.7% when compared with screening with radiography.

Percutaneous Biopsy

The true positive rate of percutaneous lung biopsy is 90%–95%. False-negative results are usually due to poor needle placement, necrotic tissue, and so on. Tumor seeding is extremely uncommon (1 in 20,000).

Contraindications to biopsy are usually relative and include:

• Severe COPD

• Pulmonary hypertension

• Coagulopathy

• Contralateral pneumonectomy

• Suspected echinococcal cysts

Classification

• Adenocarcinoma (most common), 40%:

• 2011 International Association for the Study of Lung Cancer/American Thoracic Society/European Respiratory Society international multidisciplinary classification of lung adenocarcinoma:

  • Adenocarcinoma in situ: ≤3 cm, noninvasive lepidic growth pattern (along the alveolar walls), typically nonsolid on CT, usually nonmucinous

  • Minimally invasive adenocarcinoma: ≤3 cm, primarily lepidic growth with invasive component ≤5 mm, predominantly nonsolid appearance on CT but may contain central solid component (≤5 mm), typically nonmucinous

  • Lepidic predominant nonmucinous adenocarcinoma: invasive but with mainly lepidic growth, typically part solid on CT but may have nonsolid or cystic appearance

  • Invasive mucinous adenocarcinoma: predominantly lepidic growth pattern, formerly referred to as mucinous bronchioloalveolar carcinoma , may appear solid, primarily solid, part solid, or nonsolid on CT, can be multifocal

• Atypical adenomatous hyperplasia is one of the preinvasive lesions for adenocarcinoma of the lung:

  • Typically a ground-glass nodule less than 5 mm in size

• SCC, 30%:

  • Spindle cell carcinoma

• Small cell carcinoma, 15%:

  • Oat cell

  • Intermediate cell type

  • Combined oat cell carcinoma

• Large cell carcinoma, 1%:

  • Giant cell carcinoma

  • Clear cell carcinoma

• Adenosquamous tumor

Risk Factors for Bronchogenic Carcinoma

• Smoking: 98% of male patients and 87% of female patients with lung cancer smoke; 10% of heavy smokers will develop lung cancer. The strongest relationship between smoking and cancer has been established for SCC, followed by adenocarcinoma.

• Radiation, uranium mining

• Asbestos exposure

• Genetic predisposition (HLA-Bw44 associated?)

Radiographic Spectrum

Primary Signs of Malignancy ( Fig. 1.32 )

• Mass (>6 cm) or nodule (<6 cm) with spiculated, irregular borders

• Unilateral enlargement of hilum: mediastinal widening, hilar prominence

• Cavitation

  • Most common in ULs or superior segments of LLs

  • Wall thickness is indicative of malignancy

  • Less than 4 mm: 95% of cavitated lesions are benign

  • >15 mm: 85% of cavitated lesions are malignant

  • Cavitation is most common in SCC

• Certain tumors may present as chronic ASD: adenocarcinoma, lymphoma

• Some air bronchograms are commonly seen by HRCT in adenocarcinoma.

Secondary Signs of Malignancy ( Fig. 1.33 )

• Atelectasis (Golden inverted S sign in RUL, LUL collapse)

• Obstructive pneumonia

• Pleural effusion

• Interstitial patterns: lymphangitic tumor spread

• Hilar and mediastinal adenopathy

• Metastases to ipsilateral, contralateral lung

LOCATIONS OF TUMORS

Tumor	Frequency (%)	Location	Comments
Adenocarcinoma	40	Peripheral	Scar carcinoma
Squamous cell carcinoma	30	Central, peripheral a	Cavitation
Small cell carcinoma	15	Central, peripheral a	Endocrine activity
Large cell carcinoma	1	Central, peripheral	Large mass

a Rarely present as a resectable T1 lesion.

Paraneoplastic Syndromes of Lung Cancer

• Incidence: 2% of bronchogenic carcinoma

  • Metabolic

    • Cushing syndrome (ACTH)

    • Inappropriate antidiuresis (ADH)

    • Carcinoid syndrome (serotonin, other vasoactive substances)

    • Hypercalcemia (PTH, bone metastases)

    • Hypoglycemia (insulin-like factor)

  • Musculoskeletal

    • Neuromyopathies

    • Clubbing of fingers (HPO)

  • Other

    • Acanthosis nigricans

    • Thrombophlebitis

    • Anemia

Radiation Pneumonitis

Radiation pneumonitis is the acute phase of radiation damage and usually appears 3 weeks after treatment. The minimum radiation dose to induce pneumonitis is 30 Gy. The acute phase is typically asymptomatic but may be associated with fever and cough. Fibrosis usually occurs after 6–12 months.

American Joint Committee on Cancer Tumor-Node-Metastasis (TNM) Staging System, Seventh Edition (Nonsmall Cell Lung Cancer)

• Primary tumor (T)

  • T0: No evidence of a primary tumor

  • T1: ≤3 cm, limited to lung, not more proximal than lobar bronchus

  • T1a: ≤2 cm

  • T1b: >2 and ≤3 cm

  • T2: >3 but ≤7 cm

    • Or invades parietal pleura

    • Or involves main bronchus ≥2 cm distal to carina

    • Or atelectasis/obstructive pneumonia extending to hilum but not involving entire lung

  • T2a: >3 but ≤5 cm

  • T2b: >5 but ≤7 cm

  • T3: >7 cm

    • Or directly invades chest wall, diaphragm, phrenic nerve, mediastinal pleura, parietal pericardium

    • Or mainstem bronchus <2 cm distal to carina

    • Or atelectasis/obstructive pneumonia involving entire lung

    • Or separate tumor nodules in a different ipsilateral lobe

  • T4: Any size

    • Heart, mediastinum, great vessels, trachea, recurrent laryngeal nerve, esophagus, vertebral body, or carina

    • Or separate tumor nodules in a different ipsilateral lobe

• Nodes (N)

  • N0: No lymph node involvement

  • N1: Ipsilateral nodes in the hilar, interlobar, lobar, segmental, subsegmental regions

  • N2: Ipsilateral nodes in mediastinum. Affected regions include paratracheal, prevascular and retrotracheal, lower paratracheal, subcarinal, paraesophageal, and pulmonary ligament regions.

  • N3: Contralateral hilar or mediastinal nodes; all significantly large lymph nodes in the ipsilateral or contralateral supraclavicular or scalene regions

• Metastases (M)

  • M0: No metastases

  • M1: Metastases

  • M1a: Intrathoracic metastases:

    • Tumor nodules in contralateral lung

    • Malignant pleural/pericardial effusion

    • Pleural dissemination

  • M1b: Distant (extrathoracic) metastases: liver, bone, brain, adrenal gland

5-Year Survival

Overall 5-year survival rate is 15%.

• Stage 1A: 50%

• Stage 1B: 43%

• Stage 2A (limited disease): 36%

• Stage 2B (T4): 25%

• Stage 3A (N3): 19%

• Stage 3B: 7%

• Stage 4: 2%

Small Cell Cancer Staging

Small cell lung cancer (SCLC) accounts for 15% of all lung cancers and is known for its rapid growth rate and its early dissemination to regional lymph nodes and distant sites.

Traditionally a two-stage system had been used for SCLC: “limited” and “extensive.” Limited disease is confined to one lung with ipsilateral lymph node metastasis (can be encompassed by a single radiation port) and has better prognosis. Extensive stage denotes metastases to the contralateral lung and nodes or distant organs (including the pleura). About two-thirds of patients with SCLC present at the extensive stage at the time of initial diagnosis. The International Committee for the Study of Lung Cancer now recommends that SCLC be staged with the eighth edition of the American Joint Committee on Cancer's TNM staging system.

Five-year survival rates in patients with SCLC:

• Stage 1A: 56%

• Stage 1B: 57%

• Stage 2A: 38%

• Stage 2B: 40%

• Stage 3A: 12%

• Stage 3B: 0%

Lymph Node Imaging

Anatomy ( Fig. 1.35 )

• Anterior mediastinal nodes

  • Parietal node group

    • Internal mammary nodes

    • Superior diaphragmatic nodes

  • Prevascular node group (anterior to the great vessels)

• Middle mediastinal nodes

  • Paratracheal *

    * Paratracheal and subcarinal nodes are best assessed by mediastinoscopy; the remainder of the nodes are best assessed by CT.

    ; the lowest node is the azygos node

  • Subcarinal * : below bifurcation; drainage to right paratracheal nodes

  • Subaortic; AP window node

  • Tracheobronchial (pulmonary root, hilar)

• Posterior mediastinal nodes

  • Paraaortic

  • Prevertebral

  • Paraspinous: lateral to vertebral body

American Thoracic Society Classification ( Fig. 1.36 )

This classification system assigns numbers to regional lymph nodes:

• 2R, 2L: paratracheal

• 4R, 4L: superior tracheobronchial

• 5, 6: anterior mediastinal

• 7: subcarinal

• 8, 9: posterior mediastinal

• 10R, 10L: bronchopulmonary

• 11R, 11L: pulmonary

• 14: diaphragmatic

Chest Wall Invasion

Accuracy for detection of chest wall invasion by CT is 40%–60%.

Radiographic Features ( Fig. 1.37 )

• Reliable signs

  • Soft tissue mass in chest wall

  • Bone destruction

• Unreliable signs

  • Obtuse angles at contact between tumor and pleura

  • >3 cm of contact between tumor and pleura

  • Pleural thickening

  • Increased density of extrapleural fat

Mediastinal Invasion

Contiguous invasion of mediastinal organs, heart, great vessels, aerodigestive tract, and vertebra indicates nonresectability.

Malignant Pleural Effusion

Development of pleural effusions usually indicates a poor prognosis. Presence of a documented malignant pleural effusion makes a tumor unresectable (M1). Incidence of pleural effusion:

• Bronchogenic carcinoma, 50%

• Metastases, 50%

• Lymphoma, 15%

Pericardial Metastasis

Pericardial effusion with enhanced nodules is highly suggestive of malignant involvement of the pericardium.

CT and MRI findings are inconclusive for determination of benign versus malignant pleural and pericardial disease. Fluorodeoxyglucose positron emission tomography (FDG PET) has been shown to have high sensitivity in detecting pleural malignancy.

Central Bronchial Involvement

Tumors that involve a central bronchus usually cause lung collapse or consolidation. These tumors are considered unresectable (T4 tumors) only if they involve the carina.

Metastases to Other Organs

• Lung tumors most frequently metastasize to:

  • Liver (common)

  • Adrenal glands (common)

    • 30% of adrenal masses in patients with adenocarcinoma are adenomas.

    • Most adrenal masses in patients with small cell carcinomas are metastases.

    • Tumor may be present in a morphologically normal-appearing gland.

  • Other sites (especially small and large cell tumors)

    • Brain (common)

    • Bones

    • Kidney

Adenocarcinoma

• Now the most frequent primary lung cancer

• Typically presents as a multilobulated, peripheral mass

• May arise in scar tissue: scar carcinoma

• KRAS mutation is the most frequent genetic mutation.

Bronchioloalveolar Carcinoma

• Subtype of adenocarcinoma; slow growth. The characteristic radiographic presentations are:

  • Morphologic type

    • Small peripheral nodule (solitary form), 25% (most common)

    • Multiple nodules

    • Chronic ASD

  • Air bronchogram

  • Absent adenopathy

  • Cavitation may be seen by HRCT (Cheerio sign)

Squamous Cell Carcinoma (SCC)

SCC is most directly linked with smoking. SCC carries the most favorable prognosis. The most characteristic radiographic appearances are:

• Cavitating lung mass, 30%

• Peripheral nodule, 30%

• Central obstructing lesion causing lobar collapse

• Chest wall invasion

• FGFR1 amplification is the most common mutation.

Large Cell Carcinoma

Usually presents as large (>70% are >4 cm at initial diagnosis) peripheral mass lesions. Overall uncommon tumor.

Pancoast Tumor (Superior Sulcus Tumor)

Tumor located in the lung apex that has extended into the adjacent chest wall. Histologically, Pancoast tumors are often SCCs.

Radiographic Features ( Fig. 1.38 )

• Apical mass

• Chest wall invasion

• Involvement of subclavian vessels

• Brachial plexus involvement

• Bone involvement: rib, vertebral body

Small Cell Carcinoma (SCC) (Neuroendocrine Tumor, Type 3)

Most aggressive lung tumor with poorest prognosis. At diagnosis, two-thirds of patients already have extrathoracic spread:

• Typical initial presentation: massive bilateral lymphadenopathy

• With or without lobar collapse

• Brain metastases

Carcinoid (Neuroendocrine Tumor, Types 1 and 2)

Represent 90% of low-grade malignancy tumors of the lung. The 10-year survival rate with surgical treatment is 85%. Rarely results in carcinoid syndrome caused by the production of 5-hydroxytryptamine with flushing, diarrhea, nausea, and wheezing; carcinoid syndrome usually accompanied by liver metastases.

Hamartoma ( Fig. 1.39 )

Hamartomas are mesenchymal tumors and are the most common benign tumors of the lung composed of cartilage (predominantly), connective tissue, muscle, fat, and epithelial tissue. 85% are identified as solitary pulmonary nodules, 5%–15% are endobronchial. They typically occur in individuals older than 50 years and are more common in men.

Carney Triad

Tracheobronchial Papillomatosis

Pulmonary Blastoma

• Predominant in males, poor prognosis

General

Pathways of metastatic spread from a primary extrathoracic site to lungs (in order of frequency):

• Spread via pulmonary arteries (PAs)

• Lymphatic spread (celiac nodes → posterior mediastinal nodes + paraesophageal nodes) and in lung parenchyma

• Direct extension

  • Endobronchial spread

  • Follow the invasion-metastasis cascade: invade locally, intravasate into blood, survive circulation, lodge in distant organ, merge into parenchyma, survive the foreign organ, and reinitiate growth.

Neoplasms with rich vascular supply draining into systemic venous system:

• Renal cell carcinoma (RCC)

• Sarcomas

• Trophoblastic tumors

• Testis

• Thyroid

Neoplasms with lymphatic dissemination:

• Breast (usually unilateral)

• Stomach (usually bilateral)

• Pancreas

• Larynx

• Cervix

Other neoplasms with high propensity to localize in lung:

• Colon

• Melanoma

• Sarcoma

Calcified Metastases

• Calcifications in lung metastases are observed in:

  • Bone tumor metastases

    • Osteosarcoma

    • Chondrosarcoma

  • Mucinous tumors

    • Ovarian

    • Thyroid

    • Pancreas

    • Colon

    • Stomach

  • Metastases after chemotherapy

Giant Metastases (“Cannon Ball” Metastases) in Asymptomatic Patients

• Head and neck cancer

• Testicular and ovarian cancer

• Soft tissue cancer

• Breast cancer

• Renal cancer

• Colon cancer

Sterile Metastases

Sterile metastases refers to pulmonary metastases under treatment that contain no viable tumor. Nodules typically consist of necrotic and/or fibrous tissue.