Path Image

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.


Lung : Bronchioloalveolar Carcinoma, Mucinous subtype


Zander DS, Farver CF. Pulmonary Pathology: Foundations in Diagnostic Pathology. Philadelphia, PA: Elvesier; 2008: 549-552.

Last updated: 2010-10-25
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