Prognostic value of bronchiolo-alveolar carcinoma component of small lung adenocarcinoma

Background. Bronchiolo-alveolar carcinoma (BAC) is often observed in lung adenocarcinoma, but its clinicopathological and prognostic significance, especially in small peripheral lung adenocarcinoma, remains undetermined. Methods. We assessed 206 consecutive cases of surgically resected small peripheral lung adenocarcinoma (less than 2 cm in diameter) recorded between 1973 and 1997. According to the component area of well differentiated BAC within maximally cut surface specimens of tumor tissue, we semiquantitatively classified the tumors into four types: those in which the BAC component comprised 0% (type I), 1% to 49% (type II), 50% to 99% (type III), and 100% (type IV) of the tumor tissue. Results. Forty tumors were classified as type I, 75 as type II, 74 as type III, and 17 as type IV. The tumors with less BAC, especially type I and II, showed a significantly more aggressive nodal involvement and tumor stage, and consequently a worse prognosis, while type IV tumors had no nodal involvement and the most favorable prognosis. The patients with type III showed clinicopathological characteristics somewhere between those of type II and type IV patients. Among stage I patients, however, those with type II had the worst prognosis, while those with type I showed as good a prognosis as the other two groups. Conclusions. This novel classification based on the degree of BAC involvement in small peripheral lung adenocarcinoma may reflect clinicopathological and prognostic characteristics. This classification may prove practical for planning therapeutic strategies, in particular surgical treatment.