Signet-ring stromal tumor of the ovary: a histochemical, immunohistochemical and ultrastructural study.

We report a signet-ring stromal tumour found in the ovary of a 50-year-old woman. The solid tumour was composed of spindle and round cells which stained with vimentin and some round cells were vacuolated and had the appearance of signet-ring cells. The vacuoles were negative with periodic acid-Schiff, with and without diastase digestion, with alcian blue, Sudan III, alpha-1-antitrypsin and alpha-fetoprotein stains. Ultrastructurally, they were membrane bound and contained scantly flocculent material. Some neoplastic cells contained intracytoplasmic eosinophilic globules which were positive with alpha-1-antitrypsin. Signet-ring stromal tumour is a benign, morphologically distinctive type of ovarian stromal tumour, which may present problems in differential diagnosis with other stromal and non stromal ovarian neoplasms.