Purpose: To study the histopathologic features of CT screen-detected Stage IA adenocarcinomas to determine whether survival differed by the proportion of bronchioloalveolar component (BAC) or by the presence of multiple lesions in node-negative patients.
Methods: Five pathologists with expertise in pulmonary pathology examined 279 resected cases of adenocarcinomas, 30 mm or less in length diagnosed by CT screening for lung cancer. The panel determined the consensus diagnosis for each case, identified additional cancers, and classified each case as solitary or non-solitary. The presence and proportion of BAC was also documented.
Results: Of the cases of adenocarcinoma, 20 (7%) were BAC subtype, 246 (88%) mixed subtype and 13 (5%) adenocarcinoma-OTHER. BAC cases manifested as non-solid and part solid nodules, mixed as solid and part-solid, and other as solid only. Kaplan-Meier 10-year survival rates were 100% for BAC and adeno-MIXED with 90-99% BAC cases, 95% for mixed with 1-90% BAC, 90% for those without a BAC component, and 75% for other cases. Fifty (18%) cases were non-solitary carcinomas and 44 of these were node negative; the non-solitary node-negative cases had the same excellent prognosis as solitary node-negative cases.
Conclusions: The proportion of BAC component was a positive prognostic factor and correlated with CT consistency. Contrary to staging predictions, cases of non-solitary node-negative adenocarcinoma had the same excellent prognosis as solitary node-negative cases, suggesting that most of the small, node-negative multiple carcinomas probably represent multiple primaries rather than intrapulmonary metastasis.