26. Unusual adenomatoid tumour of the ovary consisting entirely of signet ring like-cells mimicking metastatic signet ring cell adenocarcinoma

Abstract

Adenomatoid tumours of the ovary are rare benign neoplasms of mesothelial origin. They usually present as microscopic incidental findings in ovaries removed for other pathology. They are usually located within the ovarian hilum and tend to have a characteristic morphology of bland flattened to epithelioid cells with eosino-philic cytoplasm that are arranged into tubules, trabeculae and mi-crocystic spaces. We present an unusual case of an adenomatoid tumour arising wholly within the cortex of the ovary and consisting of entirely of infiltrative nests and small tubule-like structures composed of cells with a signet ring-like morphology. The im-munohistochemical profile of these cells was strong keratin posi-tivity and only weak, patchy staining for the mosethelial marker calretinin. The combination of these morphologic and immunohis-tochemical features could, under certain clinical conditions, particularly if a panel of appropriate immunohistochemical stains are not performed, lead to the over diagnosis of these benign tumours as metastatic signet ring cell adenocarcinoma. In view of the findings from our case, when considering a diagnosis of metastatic signet ring cell adenocarcinoma in the ovary, close attention must be paid to the cellular and nuclear features as well as the cytoplas-mic vacuoles to ensure that the diagnosis of adenomatoid tumour is not missed. We would also recommend using WT-1 and D2–40, in addition to calretinin, as additional evidence of mesothelial origin in a panel of immunohistochemical stains.