Study of the diagnostic difference between the clinical diagnostic criteria and results of immunohistochemical staining of multiple primary lung cancers.

Aim When multiple synchronous or metachronous lung cancer lesions are identified, discrimination of multicentric lung cancers from intrapulmonary metastases by clinical findings is often difficult. When tissue types have the same pathological features, such as combinations of squamous cell carcinoma (SCC), adenocarcinoma (AD) or bronchiolo-alveolar cell carcinoma (BAC), it is especially difficult to distinguish a 2(nd) primary lung cancer from a metastatic lesion. A new strategy for accurate diagnosis of multiple synchronous or metachronous lung cancer is needed because of the difficulty of histological discrimination. Methods Of 363 patients with primary lung cancer for which surgeries were conducted at our hospital, 7 cases were diagnosed as synchronous multiple lung cancer (BAC-BAC in 4 cases and SCC-BAC in 3 cases) and 8 cases (BAC-BAC in 2 cases, AD-BAC in 1 case, AD-AD in 1 case, SCC-AD in 1 case and SCC-SCC in 3 cases) were diagnosed as metachronous multiple lung cancer according to the clinical diagnostic criteria. This study focused on 8 cases with the combinations AD-AD, AD-BAC, or BAC-BAC. For immunohistochemical staining, we used the antibodies to 6 antigens as follows: CK-19, p53, CEA, Hup-1, PE-10, and Ki-67. Results Of 4 cases diagnosed as synchronous lung cancer according to the clinical diagnostic criteria, differing immunohistochemical stained images of the lesions were observed in 3 cases, while in the 4th case almost identical immunohistochemical stained images were obtained, which indicated the 2 lesions were the primary and metastatic focuses. Of 4 cases diagnosed as metachronous lung cancer according to the clinical diagnostic criteria, almost identical stained images were seen in 3 cases, which indicated the 2 lesions were the primary and metastatic focuses. Conclusion In general, Type A and Type B in Noguchi's BAC classification, tended to be multiple synchronous or metachronous lung cancer lesions, while AD and Type C in Noguchi's BAC classification tended to be the metastatic focus. For the focuses with tissue type of BAC-BAC, the staining using CK-19, PE-10, and Ki-67 was useful in distinguishing multiple primary lung cancer from pulmonary metastasis in cases with a combination of AD and BAC.