Microcystic Stromal Tumor of ovary; Report of a rare entity

Abstract

Abstract Introduction/Objective Microcystic stromal tumor (MCST) of the ovary is an extremely rare subtype of sex cord- stromal neoplasm first described by Irving and Young in 2009. MSCT is characterized by morphology with microcyst structure, solid cellular areas, and hyalinized fibrous stroma. The most reported tumors were stage I with good prognosis. Methods/Case Report We report a rare case of a microcystic stromal tumor of right ovary in a postmenopausal woman, measuring 25 cm in greatest dimension. The present patient underwent right ovarian tumor resection. Gross examination showed that the tumor was solid and cystic. Immunohistochemically, the tumor expressed CD10, WT1, cyclin D1 and vimentin, and nuclear immunoreactivity for β-catenin but negative for α-inhibin, calretinin, CK AE1/AE3, PLAP, SALL-4, CK7, P53, EMA, CD99, AFP, desmin, CgA, E-cadherin, and melanA. Next Generation Sequencing (NGS) showed rare, pathogenic, gain of function mutation CTNNB1 pT41I. The patient is free of disease at 1-year follow up. Results (if a Case Study enter NA) NA Conclusion MCST is a rare stromal tumor of the ovary. These tumors are considered benign neoplasms because almost all cases display unilateral, localized lesions and have benign outcomes, except for one recurrent case with familial adenomatous polyposis and another initial metastatic case with a CTNNB1 mutation (Zhang Y et al. Hum Pathol 2018, 78:171). MCST is histologically characterized by a microcystic growth pattern, solid cellular areas, and intervening hyalinized stroma, accompanied by immunohistochemical evidence of sex cord-stromal differentiation. Accumulation of nuclear -catenin was reported to be relevant to the pathogenesis of MCST (Maeda D et al. Am J Surg Pathol 2011, 35:1429). More specifically, Maeda et al. observed two cases of ovarian MCST that exhibited a CTNNB1 point mutation in exon 3 and strong nuclear immunoreactivity for -catenin. Other cases exhibited alterations of APC, which is associated with familial adenomatous polyposis (Lee SH et al. Genes Chromosomes Cancer 2015, 54: 353). MCST pathogenesis is linked to -catenin stabilization involving -catenin/Wnt signaling. In our case we found a rare pathogenic, gain of function CTNNB1 T41I c.122C>T mutation which maps within a Gsk3b phosphorylation site of the Ctnnb1 protein (UniProt.org). T41I is predicted to confer a gain of function to Ctnnb1 as demonstrated by nuclear accumulation of Ctnnb1 (Garcia-Rostan G et al. Cancer Res 1999, 59:1811). Our case further expands the histopathologic and molecular spectrum of this rare entity.