[Histopathological analysis of incidental prostatic carcinoma by step section technique]

In 244 cases treated by subcapsular prostatectomy during the period from April 1975 to December 1985, whole tissue specimens were prepared by a step section technique to examine them histopathologically in accordance with the handling agreement for prostatic cancer presented by the Urologic Society of Japan. The degree of differentiation, clinical stage of the disease, the size of the lesion and the distance to the margin were determined. Incidental carcinoma was found in 35 cases (14.3%), which increased with age. There were 21 cases of stage A1 and 14 cases of A2. Diffuse proliferation was found in 4 cases. Isolated carcinomatous focus was observed in 40 sites, and well, moderately, and poorly differentiated adenocarcinoma in 33, 3 and 4 sites respectively. The maximum diameter of cancer was below 5 mm in 80%, while the distance from the center of the carcinomatous focus to the surgical margin was within 3.5 mm in 905. Seven cases had plural lesions. These lines of evidence mentioned above may support carcinogenesis from the subcapsular region as well as multicentric origin of cancer.