Solid pseudopapillary neoplasm of the ovary: a report of 3 primary ovarian tumors resembling those of the pancreas.

We report 3 cases of a hitherto undescribed ovarian tumor histologically and immunohistochemically identical to pancreatic solid pseudopapillary neoplasms. The patients were aged 17, 21, and 57 years of age. Two tumors involved the left ovary and 1 the right ovary. They ranged from 3 to 25.5 cm and were confined to the ovary. Radiologic investigations did not show an alternative primary site. Grossly the neoplasms were solid and cystic. On microscopic examination they had mostly diffuse and pseudopapillary growth patterns. Other patterns included nested and microcystic, including cysts filled with colloid-like material. The tumor cells were monotonous and the nuclei were round to oval with pale chromatin and occasional longitudinal nuclear grooves. Clear intracytoplasmic vacuoles were noted in 2 cases, and all 3 cases showed eosinophilic globules. Mitoses and atypia were virtually absent. Immunohistochemically, all 3 neoplasms showed intranuclear positivity for β-catenin and loss of E-cadherin reactivity. All 3 tumors were negative for chromogranin, inhibin, and calretinin, although both cases evaluated for thyroglobulin were found negative. One patient has been followed for 6 years and is free of disease. The other 2 cases are recent. The tumors likely to enter into the differential diagnosis include sex-cord stromal tumors, steroid cell tumors, and struma ovarii. The morphologic and immunohistochemical similarity to pancreatic solid pseudopapillary neoplasm facilitates the accurate diagnosis of this rare ovarian neoplasm.