Signet ring cell-rich microcystic stromal tumor of the ovary: A poorly recognized variant

Microcystic stromal tumor (MST) of the ovary is a rare, recently established disease entity. Histologically, MST is characterized by intercellular microcysts and solid proliferation of stromal tumor cells with eosinophilic cytoplasm and bland nuclei separated by hyalinized fibrous bands. We report a case of an ovarian tumor that we believe fulfills the histologic and immunophenotypic characteristics of MST in a woman with familial adenomatous polyposis. Peculiar histologic findings in our case included additional features such as extensive intracytoplasmic vacuoles—signet ring cell features—with occasional psammomatous calcification. Although the presence of the signet ring cell features has been reported in other ovarian stromal tumors, we believe our case should be classified as MST due to the histologic and immunohistochemical findings along with the genetic background of the patient. Histological descriptions of MSTs with signet ring cell features with or without calcification have been reported, albeit briefly, in several articles and gynecology textbooks, but are not commonly the focus of much attention. This report might broaden the description of the morphologic spectrum of MST to include signet ring cell-rich features with or without calcification as morphologic characteristics of MST.