Background: Radiologically undetected intrapulmonary solitary nodules are sometimes found in the resected lung. When the main tumor is a well-differentiated (w/d) adenocarcinoma, especially a bronchioloalveolar carcinoma (BAC), it can be difficult to determine morphologically whether the intrapulmonary nodules are atypical adenomatous hyperplasia (AAH) or intrapulmonary metastasis (PM). The authors evaluated the accuracy of the differential diagnosis of these two lesions from the prognostic point of view.
Methods: A retrospective study was conducted of 1360 lung carcinoma patients who had undergone surgical resection. Differential diagnosis was made between AAH and PM based on the conventional histologic specimens. Their clinicopathologic features were also studied. Survival rates were compared between these two groups.
Results: AAH was found in 137 patients (10%) with resected lung carcinoma. The 5-year survival rates were 72.9% in Stage I, 60.6% in Stage II, 27.1% in Stage IIIA, 0% in Stage IIIB, and 0% in Stage IV. They were not significantly different from the figures for all patients in the corresponding pathologic stages. Seventy-six cases were diagnosed as w/d adenocarcinoma associated with AAH, whereas PM was found in 46 cases of w/d adenocarcinoma. The 5-year survival rates of AAH and PM differed significantly: 64.6% and 35.5%, respectively (P 0.0004). When a comparison was made between cases of pT1-2, N0 w/d adenocarcinoma, most of which were BAC, with PM (n = 22) and those with AAH (n = 52), the latter had significantly better survival (P = 0.0086).
Conclusions: The prognosis of resected lung carcinoma was not affected by association with AAH. The significant difference in prognosis between AAH and PM in w/d adenocarcinoma, especially in BAC, indicates that their morphologic distinction was correctly made by conventional pathologic examination in most cases.