Abstract
Abstract Objectives Microcystic stromal tumor (MST) of the ovary is an extremely rare subtype of sex cord-stromal ovarian tumor with characteristic microcystic features and stromal tumor immunophenotype. First described as a distinct ovarian neoplasm in 2009, fewer than 30 cases of MST have been reported worldwide. Methods We present a 65-year-old patient who underwent a hysterectomy and bilateral salpingo-oophorectomy for endometrial carcinoma and an enlarged right ovary detected by an abdominal CT scan. Results Grossly, the 3.6-cm ovarian mass had a smooth, firm external surface and clear demarcation from the adjacent ovarian parenchyma. Sectioning of the mass revealed solid, tan-white cut surfaces. The gross appearance of the contralateral ovary was unremarkable. Microscopic examination of the hysterectomy specimen confirmed FIGO grade 1 endometrial adenocarcinoma, endometrioid type. Stromal hyperthecosis was present in both ovaries. Unique to our case, the ovarian mass was composed of a prominent hyalinized fibrous stroma with occasional scattered nodules of small to medium cells with vacuolated cytoplasm, bland chromatin, inconspicuous nucleoli, and sparse mitotic activity. Characteristic microcystic spaces were present. The cells within these microcystic nodules were positive for β-catenin (nuclear), CD10 (membranous), and cyclin D1 (nuclear). Immunohistochemical stains for calretinin, CD56, CD99, cytokeratin AE1/AE3, EMA, inhibin, and WT-1 were negative. Conclusion The combined histologic and immunohistochemical properties of this tumor are most consistent with MST of the ovary. While the clinical behavior of this new entity appears to be benign, reported cases are limited and further investigation is needed. This report highlights a histologically unique case of MST of the ovary.
Published Version
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