Primary and Metastatic Bronchiolo-Alveolar Carcinoma

1. A study of 215 cases of metastatic pulmonary carcinoma revealed 34 (15.8 per cent) instances in which the histologic features were compatible with the diagnosis of primary bronchiolo-alveolar carcinoma. 2. The metastatic bronchiolo-alveolar tumors were found chiefly in cases of carcinoma of the pancreas, colon, breast, stomach, and kidney, respectively. 3. Bronchiolo-alveolar carcinoma is not a specific entity, but a histologic pattern of malignant epithelial proliferation occurring both in primary and metastatic lung cancer. 4. The distinctive glandular appearance is dependent on the anatomic structure of the lung parenchyma which provides an alveolar stroma along which the malignant cells can propagate. The histologic differentiation between primary and metastatic bronchiolo-alveolar carcinoma presents a diagnostic challenge in the absence of necropsy.