Bronchioloalveolar Carcinoma

Bronchioloalveolar carcinoma is a subtype of adenocarcinoma and represents 2-6% of all lung cancers. It typically arises distal to the terminal bronchioles and spreads along the preexisting alveolar septa without causing significant amounts of lung destruction. This is known as a lepidic growth pattern.

Bronchogenic carcinoma is the most common visceral malignancy in males. (Skin cancers are actually the most common malignancy in adults of both sexes, but they are not visceral malignancies.) These cancers account for >16% of all cancer in males, and > 30% of all cancer deaths in males; lung cancer accounts for >13% of the cancer found in females, presumably due to the increased incidence of smoking in females. Most lung cancer occurs most commonly (98% of the time) between the ages of 40 and 70, with a peak incidence in the sixth or seventh decade; only 2% of lung cancer is seen prior to age 40.

Bronchogenic carcinoma begins as an area of in situ cytologic atypia, which over time forms a small area of thickening or piling up of bronchia mucosa. Over time, the tumor takes on an elevated irregular, warty appearance that erodes the epithelial lining of the airway.

This specimen demonstrates the varied pathways the tumor can follow. The tumor may fungate into the bronchial lumen, causing an obstructive intraluminal mass. Erosion into the surrounding parenchyma can promote peribronchial infiltration. Note the warty, irregular appearance of the tumor t at the bifrucation of the trachea in this specimen. The trachea and a second order bronchus have been stented open to demonstrate the lesion which has also erroded into surrounding tissue, including the paratracheal lymph nodes n. The right mainstem bronchus b appears completely occluded by tumor.

Relatively noninvasive diagnostic techniques include bronchial washings for cytologic examination and bronchoscopic biopsy.

Most bronchogenic carcinomas appear as irregular gray-white masses which are firm to hard in consistency. Bulky tumors may contain focal areas of hemorrhage or necrosis and may appear yellow-white in color, with central softening and necrotic cavitation, as seen in this large tumor. Note the area of necrotic cavitation c, and areas of focal hemorrhage arrow.

Local extension to the pleural surface and then within the pleural cavity may also occur.

The bronchogenic carcinoma pictured here has invaded the adjacent pleura arrows, and eroded through the pleura into an adjacent rib r.

Note also the necotic center of this irregular shaped mass.

80% of all lung cancers occur in smokers, and in retrospective studies of patients who died from bronchogenic carcinoma, a positive relationship between tobacco smoking and lung cancer was identified. Average cigarette smokers have a 10 x increased risk of developing lung cancer, while smokers who smoke 2 packs/day or more have a 20x increased risk for lung cancer. Cigar and pipe smoking modestly increase the risk for lung cancer. Screening for lung cancer using CXR has not been shown to reduce the morbidity and mortality from these lesions. This CXR shows the typical radio-opaque appearance of these lesions.

Radiation exposure, and occupational exposures to nickel, asbestos, uranium, chromates, coal, mustard gas, arsenic, beryllium and iron also increase the risk of lung cancers.

Histologically, the tumors are well-differentiated, with a peg-like cellular growth along alveolar walls.

The cells secrete mucin and surfactant apoprotein.

This can lead to bronchorrhea which is an excessive discharge of mucus from the air passages of the lungs. Although bronchioloalveolar carcinoma usually spreads through the airways, it may also metastasize by lymphatic and hematogenous routes.

Due to this growth pattern, the metastatic and local invasive potential of this tumor is unpredictable.

Consequently, histological findings are not useful in predicting survival. Unlike other adenocarcinomas, bronchioloalveolar carcinoma often develops multifocally. Patients with extensive consolidation or multifocal disease have a poor prognosis.

The lepidic growth pattern may result in lesions of heterogeneous radiologic opacity. In a few cases the tumor resembles lobar pneumonia, and this pattern also has a poor prognosis.

Bronchioloalveolar carcinoma can manifest as a single peripheral nodule or mass usually in the upper lung.

Most commonly, this nodule is well-circumscribed.

This form of tumor has a better prognosis for surgical resection. However, because of the multifocal nature of this disease, patients should be carefully evaluated for other disease before considering surgical resection