CTNNB1 Mutations in Ovarian Microcystic Stromal Tumors: Identification of a Novel Deletion Mutation and the Use of Pyrosequencing to Identify Reported Point Mutation.

Abstract

Microcystic stromal tumor (MCST) is a rare stromal tumor of the ovary. In this study, we describe clinicopathological characteristics and results of mutational analyses of the CTNNB1gene in two cases of ovarian MCST and we provide a thorough review of previously published cases alongside our current cases and clarify the clinicopathological characteristics of ovarian MCST. Patients' age was 33 and 31 years, respectively. One patient presented with fever and low abdominal pain, whereas a pelvic mass was incidentally detected in another patient. Grossly, the cut surface of the tumors was mixed solid and cystic. Histologically, the tumor characteristically displayed numerous microcysts, solid cellular areas, and intervening hyalinized stroma. Areas of moderate-to-severe nuclear pleomorphism with occasional multinucleated giant cells and bizarre nuclei were noted in one of the two cases. Immunohistochemically, both cases demonstrated diffuse and strong β-catenin expression in the nuclei and the cytoplasm. The tumor cells were also diffusely positive for CD10, vimentin, Wilms tumor 1, and cyclin D1. The tumor cells were consistently negative for E-cadherin, inhibin-α, calretinin, estrogen receptor, and progesterone receptor. Mutational analyses using direct sequencing and pyrosequencing methods exhibited a single nucleotide mutation in CTNNB1 exon 3 (c.122C>T) in one case. We also found a novel deletion mutation in the same exon (c.88_99delTACCTGGACTCT) in another case. We demonstrated a previously reported CTNNB1 point-mutation using pyrosequencing and a novel deletion mutation in ovarian MCSTs. The review of the literature of previously published cases in combination with our current cases clarifies the clinicopathological characteristics of ovarian MCST and the comprehensive analysis of these cases would expand our knowledge regarding ovarian MCST.