Adeno-in-situ is another term for bronchoalveolar adenocarcinoma, a variant of which main lung cancer category?

• A. Small Cell
• B. Adenocarcinoma
• C. Squamous Cell
• D. Large Cell

Answer: (B)

Adeno-in-situ refers to bronchioloalveolar carcinoma, which is a form of adenocarcinoma. In the lung, cancers are broadly divided into small cell and non-small cell lung cancer. The non-small cell category includes adenocarcinoma, squamous cell, and large cell carcinomas. Bronchioloalveolar carcinoma (BAC), historically called adeno-in-situ when noninvasive, grows along alveolar walls in a glandular, mucin-producing pattern—characteristic of adenocarcinoma. Therefore, this entity is a variant of adenocarcinoma within the non-small cell lung cancer group. It’s not small cell (neuroendocrine and typically more central and aggressive), nor is it a squamous or large cell carcinoma, which have different histologic features.