Feature Summary of Ovarian Microcystic Stromal Tumor:
Rare sex cord-stromal tumors.
Histological triad of microcyst, solid cellular area, and hyalinized fibrous stroma.
Positive for CD10, WT1, cyclin-D1.
Negative for ER, PR, inhibin, and calretinin.
Largely benign.
Rare malignant cases with CTNNB1 mutation.
Microcystic stromal tumors (MCSTs) of the ovary are rare sex cord-stromal tumors that are considered benign neoplasms initially described in 2009. Almost all cases display unilateral, localized lesions and benign clinical outcomes. It is characterized morphologically by a triad of microcysts, solid cellular areas, and hyalinized fibrous stroma in variable proportion in individual cases although some tumors showed a predominant solid growth pattern. The cells typically demonstrate epithelioid morphology with bland cytological appearances and infrequent mitotic figures, but focal degenerative ‘symplastic’ nuclear atypia may be seen as in other ovarian sex cord-stromal tumors. Accurate diagnosis is important in view of the generally benign clinical behavior of MCST, and its occasional association with familial adenomatous polyposis. The characteristic immunohistochemical profile includes positive stains for CD10, WT1, SF1, cyclin D1, and nucleocytoplasmic beta-catenin, and the lack of expression of estrogen receptor, progesterone receptor, inhibin, and calretinin. Recently, it has been reported that rare cases of MCST harbor CTNNB1 mutation and show a strong β-catenin nuclear immunohistochemical stain. Rare malignant MCSTs have also been reported. MCSTs should be differentiated from cystic granulosa cell tumors of the ovary. (222 words)
Key References
Wilson, Yancey et al. “Microcystic stromal tumour arising in association with serous cystadenoma.” Pathology vol. 53,7 (2021): 940-942. doi:10.1016/j.pathol.2021.02.018
Kojima, Naoki et al. “Microcystic stromal tumor of the ovary: a recurrent case with somatic CTNNB1 missense mutation.” Virchows Archiv : an international journal of pathology vol. 481,5 (2022): 799-804. doi:10.1007/s00428-022-03360-1
Boyraz, Baris et al. “Cystic Granulosa Cell Tumors of the Ovary: An Analysis of 80 Cases of an Often Diagnostically Challenging Entity.” Archives of pathology & laboratory medicine vol. 146,12 (2022): 1450-1459. doi:10.5858/arpa.2021-0385-OA
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