Objectives:To study the clinicopathological features of extraovarian peritoneal serous papillary carcinoma.Methods:The clinical pictures and pathological characteristics of 6 cases extraovarian peritoneal serous papillary carcinoma admitted to our hospital from 1992 to 1999 were studies retrospectively.H & E staining,histochemical staining and immunohistochemical staining were used.Results:The ages of the 6 patients were between 32～62(43.7) years old.The bilateral ovaries and fallopian tubes were almost normal.Tumors were examined histomorphologically by microscope and electron microscope,periodic acid-Schiff (PAS) stain was used in the histochemical study and carcinoembryonic antigen (CEA),CA125,p53,AE1 and AE3 monoclonal antibody assays were detected immunohistochemically.The results revealed no difference between extraovarian peritoneal serous papillary carcinoma and ovarian serous papillary carcinoma.Conclusions:Extraovarian peritoneal serous papillary carcinoma is considered arising from the secondary Müllerian system.Histologically,extraovarian peritoneal serous papillary carcinoma was identical to that of the similar epithelial carcinomas arising from the ovaries.The diagnosis was made only when the ovaries were not involved and without any evidence of similar epithelial carcinoma obtained in the ovaries.Histochemical staining and immunohistochemical staining are helpful as accessory criteria for the differential diagnosis between primary carcinoma of the peritoneum and malignant mesothelioma.The prognosis is poor.