Investigations of two cases of relapses of granulocellular tumors of the ovaries established their characteristics: cyst formation in nodes of the tumor growing on the peritoneum, formation of Call-Exner strucutres characteristic of the ovary tissue in tumors, and growth of the tumor on serous integument without ingrowing into the parenchyma of the abdominal cavity organs. The similarity of the observed characteristics of peritoneal tumor with typical signs of the ovary tumors suggests that mesothelium retains some properties common to those of the ovary tissue and acquired in embryogenesis.