3 cases of pleural form in 112 patients who had been diagnosed as primary cancer of the lung in our department were reported. The 1st and 3rd cases were accompanied by carcinomatous pleurisy with hemorrhagic effusion. In autopsy, the former showed diffuse carcinomatous infiltration of the pleura in the right side, and the latter a wide-spread dissemination to the pleural surface and both showed no main tumor masses in the lung parenchyma except in the marginal region of the apex. The 2nd case showed the pachypleuritis type with accompanying no pleural effusion in the clinical course and could not be differentiated from the pleural mesothelioma even in autopsy findings.
Histologically, the 1st and 2nd cases were differentiated adenocarcinomas; and the 3rd case, low differentiated adenocarcinoma. Microscopically, tumor cells showed a tendency of invasion to the subpleural and peribronchial lymph canals in all cases.
Primary herds of the carcinoma in the 1st and 3rd cases were supposed to be in the subpleural parenchyma of the apical regions of the right lung, and the 2nd case was obscure.
