Nonmucinous BAC demonstrates lepidic growth of neoplastic cells with a hobnail morphology. The cells resemble either Clara cells or type 2 pneumocytes.
Prominent intranuclear inclusions can be appreciated in this image.
By contrast, the edge of this otherwise conventional adenocarcinoma shows a peripheral lepidic growth pattern. BAC features are common in adenocarcinoma and should not be diagnosed as bona fide or pure BAC.
Bronchioloalveolar carcinoma (BAC) is considered a variant of adenocarcinoma of the lung. BAC has very distinct clinical and pathologic features. For example, compared to other NSCLC (non small cell lung cancers), BAC is over-represented in women, non-smokers and Asians. BAC is considered to be an in situ carcinoma, therefore, one must carefully examine and section the whole lesion to exclude the possibility of invasion. Approximately 20% OF NSCLCs contain a component of BAC and these tumors are called adenocarcinomas with BAC features or mixed adenocarcinomas.
BACs may be mucinous, nonmucinous or a mixture of both. Histologically, the non-mucinous type exhibits lepidic growth of neoplastic cells which resemble Clara cells (peg-shaped cells with cytoplasmic snouts and eosinophilic cytoplasm) or type II pneumocytes (cuboidal or dome-shaped cells with cytoplasmic vacuoles and occasionally intranuclear inclusions (Zander).
For more information regarding BAC, please visit our case "Bronchioloalveolar Carcinoma, Mucinous subtype" referenced below.
Zander DS, Farver CF. Pulmonary Pathology: Foundations in Diagnostic Pathology. Philadelphia, PA: Elvesier; 2008: 549-552.