Solitary, Non-mucinous Bronchioloalveolar Carcinoma (BAC)

A solitary, subpleural nodule, 2.4 x 1.8 x 1.4 cm, was resected from the right lower lobe of a 76-year-old, asymptomatic woman. There was retraction of the pleura (pleural dimple) over the nodule. The cut surface was firm and white. Accompanying lymph nodes did not contain tumor. The diagnosis was bronchioloalveolar carcinoma, solitary, nonmucinous, invading pleura. Stage (pT2N0MX) I B

This tumor illustrates many features of solitary, nonmucinous BAC. At the edge, tumor abruptly replaces normal alveolar lining cells. There is also a mild increase in fibrosis in the alveolar walls.

Near the pleura (top), the tumor shows a papillary pattern with thin, connective tissue cores covered by tumor cells. This is another common pattern that is usually present focally in solitary BAC. It must be distinguished from the more complex branching pattern seen in papillary carcinoma.

Toward the center of the tumor, the fibrosis increased markedly (pale pink zone), isolating spaces lined by tumor. This fibrosis--a sclerosing pattern--represents collapse of alveoli and is associated with the retraction of the pleura over the tumor--the dimpling. Although the term scar cancer has been used for these tumors, it is now believed that the tumor causes the scar to form, rather than that a preformed scar causes the cancer.

What is meant by scar cancer? It used to be thought that many peripheral lung cancers, especially adenocarcinomas, originated in a previous scar. More recently, for reasons summarized below, this concept has been questioned. However, there are instances where traumatic wounds (bullet or knife wounds) have been associated with cancer years later. Also, diffuse pulmonary fibrosis predisposes to lung cancer, but there is still controversy about whether asbestos, a carcinogen, causes lung cancer because of scarring or by some other mechanism.

Evidence Suggesting That Scar Results from Tumor

Reference

Flance I. Scar cancer of the lung. JAMA 1991; 266:2003-2004.

Cell types in BAC

 

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