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Lung and Pleura


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Non-neoplastic diseases of the lung are usually diagnosed by bronchoalveolar lavage, transbronchial biopsies, and open lung biopsies. In institutions with lung transplant programs, chronically diseased recipient lungs (explants) are also submitted for examination and these patients are monitored by serial biopsies to exclude graft rejection.

Symptomatic lung tumors may be sampled by fine-needle aspiration or endo/transbronchial biopsy for diagnosis. Patients without evidence of distant metastases may also proceed directly to mediastinal staging, video-assisted closed chest lung biopsy, or open lung surgery.

The United States Preventive Services Task Force recommends annual low-dose computed tomography screening for lung cancer for individuals between the ages of 55 and 80 years with a 30-year history of smoking and who either currently smoke, or who stopped smoking within the last 15 years. Screening detects asymptomatic lesions that are often small (<2 cm) and are of low density (ground glass opacities). Lesions that require biopsy include those that are increasing in size and solid or partially solid masses. It can be very difficult to localize these lesions and to obtain adequate sampling by needle biopsy for diagnosis. Limited lung surgery may be performed as some of these lesions are benign and others will prove to be adenocarcinoma in situ or minimally invasive carcinoma. It is likely that pathologists will see increasing numbers of lung resections for lesions that require preoperative localization by imaging.

Lung

RELEVANT CLINICAL HISTORY

In addition to age and gender, clinical history is often necessary or helpful for interpretation of specimens from the lung and pleura ( Table 22.1 ).

Table 22.1
RELEVANT CLINICAL HISTORY FOR LUNG SPECIMENS
HISTORY RELEVANT TO ALL SPECIMENS HISTORY RELEVANT FOR LUNG SPECIMENS
Organ/tissue resected or biopsied Tobacco use
Purpose of the procedure Occupational lung disease
Gross appearance of the organ/tissue/lesion sampled Asbestos exposure
Any unusual features of the clinical presentation Infection (known or suspected)
Any unusual features of the gross appearance Radiologic features: Ground glass opacity vs. solid mass(es); single mass vs. multiple masses; diffuse lung disease
Prior surgery/biopsies—results Screening for lung cancer
Prior malignancy Systemic diseases that affect the lungs (e.g., rheumatoid, arthritis, sarcoidosis)
Prior treatment (radiation therapy, chemotherapy, drug use that can change the histologic appearance of tissues) Organ transplantation
Compromised immune system

Biopsy, Endobronchial, Transbronchial

These biopsies are processed as described under “Biopsies.” Special studies for organisms (Gram, AFB, and MSS stains and immunohistochemical studies for mycobacteria) should be ordered if the patient is immunocompromised or if infection is suspected clinically.

During these procedures cytology specimens are often obtained as well (e.g., bronchial brushings and/or bronchial lavage).

Rarely, smears on glass slides may also be submitted by the clinician. Smears are submitted for staining only if the patient is critically ill and the results would be available prior to the tissue sections. For example, if the specimen arrives in the morning, special stains for organisms could be performed the same day.

Transplant Lung Biopsies

Transbronchial biopsies of transplant lungs may be performed on an emergency basis for symptomatic patients or as routine follow-up biopsies after transplantation. An adequate specimen consists of at least five pieces of well-expanded alveolated lung parenchyma. Gentle agitation of the specimen in formalin will help to inflate the fragments.

Tissue should only be taken for special studies for certain clinical indications and the need for these studies should be discussed with the clinician prior to acquisition of the specimen (e.g., tissue for electron microscopy or immunofluoresence studies).

Open Biopsies

Open lung biopsies are most commonly performed on ill patients with a wide differential diagnosis. These specimens are usually evaluated intraoperatively.

Wedge Resection

Wedge resections are open lung or video-assisted closed chest biopsies performed to sample focal suspicious lesions (e.g., pleural based nodules, small masses, or ground glass opacities) or to resect known tumors if the patient cannot tolerate a more extensive procedure. Bullectomies may be performed on patients with severe emphysema to improve pulmonary function (i.e., lung volume reduction surgery).

PROCESSING THE SPECIMEN

  • 1.

    The specimen is usually a triangular segment of lung and pleura with two intersecting staple lines at the margin. Record the dimensions of the specimen. Examine the pleura for any evidence of disease:

  • Normal pleura: Normal pleura is smooth and glistening. If there is an underlying mass, uninvolved pleura will be freely mobile over the mass. The absence of pleural involvement is important to document for staging lung carcinomas and can usually be determined by a good gross examination.

  • Abnormal pleura : Inflammation or tumor involving the pleura causes retraction. The pleura becomes fixed to the underlying mass. If the outer surface of the pleura is intact, it will remain smooth and glistening. If the outer surface is involved, it will appear dull and roughened. There may be adhesions on the pleura consisting of adipose tissue or skeletal muscle of the chest wall. Tumors can invade across adhesions into the chest wall. This is a margin and an important area to evaluate for tumor extent and staging. Areas of suspected pleural involvement can be inked a specific color and evaluated microscopically.

  • Tumor implants : Tumor implants form gray/white nodules within the pleura.

  • Lymphangitic spread of tumor : Extensive lymphovascular invasion has the appearance of thin white anastomising lines running through the pleura.

  • Pleural lymph nodes : Normal lymph nodes form small black firm ovoid nodules in the pleura.

  • 2.

    Record the length of the margin which is usually a staple line or lines.

  • It is possible to examine the true margin located just beyond the staple line during intraoperative consultation in selected cases for lesions close to this margin. This method stabilizes a tissue section in frozen embedding medium which allows staples to be removed while limiting the damage to the tissue.

  • Outside of intraoperative consultation, attempting to remove staples from nonfrozen tissue only shreds the tissue and renders it uninterpretable.

  • Cut the staple line off the specimen with a pair of scissors, staying as close to the staples as possible. The cut surface of the lung now visible is the closest margin which can be evaluated. This margin can be sampled en face or, if the tumor is close, taken perpendicularly after inking the open surface. Blot the lung free of any fluid before inking to prevent the ink from smearing.

  • 3.

    Serially section through the remainder of the specimen looking for any focal lesions. Describe all lesions including size, color, involvement of pleura, and distance from margin.

  • 4.

    Describe the remainder of lung parenchyma (emphysematous changes, consolidation, fibrosis).

  • 5.

    The histologic appearance of even small lung specimens can be improved by inflating the fragment with a syringe filled with formalin. However, great care must be taken not to injure unprotected fingers!

  • 6.

    Submit representative sections of any lesion including relationship to the pleura and uninvolved lung. Submit the closest margin. Submit one cassette of uninvolved lung parenchyma.

  • 7.

    If the margin is close, the surgeon may submit an additional section of lung with two staple lines as the new margin. If no gross lesions are present, submit two representative sections perpendicular to the margin.

Wedge Resection—Image Guided

Lung imaging by CT can detect small lesions (< 2 cm) and lesions of low density (ground glass opacities). If these lesions are evaluated by a wedge resection, it may be very difficult or impossible for the surgeon to identify the location of the lesion intraoperatively by palpation. Multiple methods have been devised to help surgeons identify these lesions including percutaneous injection of dye and image guided placement of wires, hooks, or T bars. A T bar consists of a thin wire with a short perpendicular thicker bar at the end and may be placed under CT guidance immediately before surgery. The “T” shape helps anchor the wire in the lung parenchyma.

A specimen radiograph may be taken to document the presence of the device used to localize the lesion. It is unlikely that the lesion will be visualized in the radiograph due to the types of lesions localized (small and/or of low density) and the collapse of the surrounding lung tissue after excision.

It can be challenging for the pathologist to identify these lesions due to the small size and typical diffuse growth pattern. About 75% are carcinomas and 25% benign lesions. A “ground-glass opacity” has the appearance on imaging of an area of increased density with preserved vascular and bronchial markings. The histologic correlate is thickened alveolar septa or partial filling of air spaces with fluid, cells, or debris. Carcinomas typically presenting as ground-glass opacities include adenocarcinoma in situ, minimally invasive adenocarcinoma, and lepidic pattern adenocarcinoma. Lymphoma, as well as inflammatory lesions (e.g., “coin pneumonia”), can also have this appearance.

These specimens may be referred to as image guided video assisted thorascopic surgery (iVATS) specimens.

PROCESSING THE SPECIMEN

  • 1.

    If a specimen radiograph is available, determine the location of the tip of the wire in the specimen and if the targeted lesion is visible. It is helpful to be aware of the type of lesion (mass or ground glass opacity) and size by imaging.

  • 2.

    The specimen is typically a triangular segment of lung and pleura with two intersecting staple lines at the margin. Record the dimensions of the specimen and the lengths of the staple lines. Examine the pleura for any evidence of disease.

  • 3.

    The wire should protrude from the specimen. The specimen can be gently palpated to identify the location of the tip of the wire.

  • If a mass can be palpated, the specimen is sliced in the plane of the mass up to the staple line. Any areas of pleural involvement are noted. The size of the mass and distance to the margin is noted.

  • If a mass cannot be palpated, the entire specimen is thinly sectioned up to the staple line. Each slice is visually inspected and gently palpated. Carcinomas with a predominant lepidic pattern can have the gross appearance of an area that is slightly firmer than normal lung parenchyma and paler in color.

  • 4.

    The closest margin can be taken as a perpendicular section after the staple line is closely removed or as a section including the staple line margin during an intraoperative consultation.

  • 5.

    Serially section through the remainder of the specimen looking for other gross lesions. Describe all lesions including size, color, involvement of pleura, and distance from margin.

  • 6.

    Describe remainder of lung parenchyma (e.g., emphysematous changes, consolidation, fibrosis).

  • 7.

    Lesions should be completely submitted for microscopic evaluation. If a definite lesion is not identified grossly, the entire area of lung near the tip of the wire should be submitted.

Pneumonectomy or Lobectomy

Pneumonectomies and lobectomies are almost always performed to resect tumors. An exception is the recipient pneumonectomy prior to lung transplant. These are described in a separate section below. Extrapleural pneumonectomies are used rarely to resect mesotheliomas, some locally advanced pulmonary carcinomas and sarcomas, and are also described separately.

A “sleeve lobectomy” may be used to remove a centrally located tumor while preserving lung parenchyma. The distal portion of the lobe is excised and the bronchus anastomosed to the remaining main bronchial stump. The specimen consists of the lobe with a segment of bronchus and stapled parenchyma. Additional margins include the distal bronchus and the parenchyma.

Lung Tumors

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