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Neuroendocrine Neoplasms

Introduction Neuroendocrine neoplasms include a spectrum of malignant neoplasms ranging from relatively low- to intermediate-grade malignancies (typical and atypical carcinoid [AC] tumors) to high-grade malignancies (small cell carcinoma, large cell neuroendocrine carcinoma) and are among the most aggressive primary lung neoplasms. Over the last decade, the individual diagnostic categories have become better defined histologically; the most recent (2015) version of World Health Organization (WHO) classification system…

Usual Lung Cancers

Introduction Non–small cell lung cancer (NSCLC) is the second most common cancer diagnosed in the United States and the leading cause of cancer-related mortality, with an estimated 221,200 new cases and 158,040 deaths anticipated in 2015. Lung cancer was the leading cause of cancer death among men in 2012. Among women, lung cancer was the leading cause of cancer death in more developed countries and the…

Other Nonneoplastic Focal Lesions, Inclusions, and Depositions

Introduction This chapter addresses a variety of lung lesions that represent repair reactions, inclusions, deposition disorders, and masses of uncertain etiology. They may present as single or multiple lesions or as infiltrative lesions. They may be secondary to systemic diseases, but unlike those diseases in Chapter 35 , they represent masses or infiltrates that are secondary depositions of material (amyloidosis, light chain deposition disease, calcifications). They…

Transplantation-Related Lung Pathology

Complications of Lung Transplantation Lung transplantation, whether single, bilateral, or, less often, heart–lung, has been an accepted mode of therapy for a variety of end-stage lung diseases for about 25 years. The most common indications for transplantation in adults are emphysema, cystic fibrosis (CF), idiopathic pulmonary fibrosis, sarcoidosis, and primary pulmonary hypertension (PPH), whereas for children most common indications are CF and PPH. Advances in donor…

Uncommon Histiocytic and Dendritic Cell Proliferations

Introduction The mononuclear phagocyte system includes monocytes, macrophages/histiocytes, and dendritic cells. Macrophages/histiocytes are tissue-based cells that have an important phagocytic function and produce a variety of bioactive substances that play roles in inflammation and fibrosis. Alveolar macrophages are a normal constituent cell population in the lungs, and pulmonary histiocytic accumulations are not an uncommon finding in this location, occurring in some infections, pneumoconioses, sarcoidosis, storage diseases,…

Lymphoid Lesions of the Lung

Introduction Pulmonary lymphoproliferative disorders encompass a spectrum of benign and malignant lymphoid proliferations. Benign proliferations include intraparenchymal lymph nodes, follicular bronchiolitis, lymphoid interstitial pneumonia (LIP) (sometimes encompassed under the term diffuse lymphoid hyperplasia ), localized pulmonary “nodular” lymphoid hyperplasia, and pulmonary involvement by IgG4-related disease. Malignant lymphoproliferative disorders include pulmonary marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT), pulmonary lymphomatoid granulomatosis (LYG), posttransplant lymphoproliferative disorder,…

Diseases of Small Airways

Introduction Bronchiolitis is a general term used to describe inflammatory lung diseases primarily affecting the small conducting airways and often (but not always) sparing the more distal lung parenchyma. It may occur in isolation, but sometimes it may be a component of a disease involving proximal airways (bronchiectasis, asthma). Bronchiolitis occurs in a wide variety of clinical settings ( Table 21.1 ) and manifests varied histopathologic…

Emphysema and Diseases of Large Airways

Introduction The disorders included in this chapter are grouped under the heading “obstructive lung diseases.” These diseases share the characteristic of increased resistance to airflow, which can be caused by either an increase in the resistance of the conducting airways or an increase in lung compliance due to emphysematous lung destruction, or both. The airflow limitation is usually progressive and is associated with an abnormal inflammatory…

Drug Reactions and Other Iatrogenic Pulmonary Diseases

Introduction Drug-induced lung injury is common and can be induced by a wide variety of drugs used for treatment of many different clinical conditions. More than 600 prescribed medications have been reported to cause drug-induced pulmonary toxicity. Adverse drug reactions have been estimated to occur in approximately 5% of all patients receiving any drug and are responsible for up to 0.03% of all hospital deaths. Although…

Environmental- and Toxin-Induced Lung Diseases

Introduction Exposures to environmental agents can result in a wide spectrum of pulmonary pathologic patterns ( Table 18.1 ). The most common reactions are chronic due to exposure to mineral(s) over a cumulative period and have latencies often exceeding several decades. Acute reactions are usually now the result of industrial accidents, where exposures are relatively brief but extremely high. Occupational histories need to be detailed and…

Other Interstitial Lung Diseases

Hypersensitivity Pneumonitis Hypersensitivity Pneumonitis—Fact Sheet Definition ▪ Diffuse interstitial granulomatous pneumonitis, caused by exposure to inhaled organic antigens or other particles of small size in susceptible individuals ▪ Large number of syndromes associated with specific triggering agents; major categories of agents include fungi, bacteria, and animal proteins Incidence and Location ▪ Worldwide distribution ▪ Prevalence varies depending on geographic location and shows a seasonal variation for…

Idiopathic Interstitial Pneumonias

Introduction Idiopathic interstitial pneumonias comprise a number of relatively uncommon clinicopathologic entities, which can be distinguished from one another and from other forms of diffuse interstitial lung disease by their clinical, radiologic, and histologic features. The basic approach to diagnosing these entities is included in American Thoracic Society/European Respiratory Society (ATS/ERS) consensus statements from 2002, 2011, and 2013. The major entities referenced include idiopathic pulmonary fibrosis…

Chlamydial, Mycoplasmal, Rickettsial, and Ehrlichial Diseases

Introduction The unusual bacterial pneumonias described in this chapter are caused by agents that are phylogenetically diverse and reside in a wide variety of locations, ranging from extracellular Mycoplasma attached to respiratory epithelium to obligately intracellular organisms. The obligately intracellular agents range from Rickettsia and Orientia, living in the cytosol of endothelial cells, to Chlamydia, Ehrlichia, and Anaplasma, living in modified cytoplasmic vacuoles. Coxiella, a facultatively…

Human Parasitic Pulmonary Infections

Introduction Parasitic infections remain an important cause of pulmonary disease throughout the world, although less frequently encountered in resource-rich countries. The most common protozoal parasite–associated lung diseases throughout the world are caused by Plasmodium falciparum (falciparum malaria) and Toxoplasma gondii (toxoplasmosis). Helminths cause a variety of pulmonary diseases. The most common diseases caused by nematodes include the transient disease associated with transpulmonary migration, the aberrant migration…

Viral Diseases

Introduction Influenza viruses remain the most frequently identified causes of viral infection in the lung, and respiratory syncytial virus (RSV) remains a major cause of severe pneumonia in children worldwide and is an increasingly recognized cause of illness in adults and elderly patients. Other agents, such as rhinovirus (RV), have been increasingly detected mirroring advances in molecular and serologic diagnostic techniques and increased surveillance programs. Nonetheless,…

Fungal Diseases

Introduction Fungi are unicellular or multicellular organisms that have chitinous cell walls and reproduce asexually, sexually, or both ways. Fungal cells are larger and more complex than bacteria, with cell walls containing polysaccharides, proteins, and sugars. Pulmonary fungal infections typically follow inhalation of aerosolized fungi from the environment. The infections can remain either localized to the lungs or can disseminate to produce systemic disease in immunocompromised…

Mycobacterial Diseases

Tuberculosis Tuberculosis—Fact Sheet Definition ▪ Infection caused by MTB Incidence and Location ▪ About one-third of people throughout the world are infected with MTB ▪ Tuberculous disease develops in approximately 10% of infected individuals ▪ Infection is most commonly diagnosed in the elderly and people with HIV infection Morbidity and Mortality ▪ Mortality is extremely uncommon in treated patients ▪ Morbidity depends on the severity and…

Bacterial Diseases

Introduction Bacterial infections in the lung can be classified in many different ways, that is, pathogenesis, epidemiology, anatomic distribution (lobar or bronchopneumonia), time course, or etiologic agent. In practice, a combination of these approaches is needed to classify bacterial pneumonias. Indeed, the clinician and pathologist usually require clinical, pathologic, and microbiologic information to diagnosis most pneumonias. Therefore for the purposes of this chapter, we will discuss…

Acute Lung Injury

Introduction The term acute lung injury pattern was originally proposed by Katzenstein to encompass the histologic entities of diffuse alveolar damage (DAD) and the entity previously referred to as bronchiolitis obliterans with organizing pneumonia (BOOP), now known as organizing pneumonia pattern (OP). This designation was designed to reflect the relatively acute onset of both entities, as well as the uniformity of both processes reflective of injury…

Vasculitides and Other Causes of Pulmonary Hemorrhage

Introduction The diagnosis and classification of pulmonary vasculitis is a challenging topic because pulmonary vasculitides represent pulmonary manifestations of systemic diseases. Extrapulmonary involvement is, in some cases, a significant source of morbidity and mortality. To further complicate matters, there is considerable overlap in the histologic patterns of manifestations from different systemic vasculitis syndromes, as well as secondary inflammatory processes that affect blood vessels as seen in…