Microcystic stromal tumor of the ovary: a recurrent case with somatic CTNNB1 missense mutation.

Microcystic stromal tumors (MCSTs) of the ovary are rare sex cord-stromal tumors that 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. We report herein a sporadic case that relapsed as intra-abdominal spread 9 years and 1 month after primary left salpingo-oophorectomy for torsion of the ovarian tumor pedicle. The tumor relapsed as multiple disseminations at the subabdominal wall, Douglas pouch, and omentum. Histologically, the tumor cells formed microcysts and infiltrated the surrounding adipose tissue, similar to the invasive implants of ovarian epithelial borderline tumors. Mutation analysis of the recurrent tumor revealed a somatic CTNNB1 p.S33Y activated missense mutation and a germline KDR p.Q472H variant. In conclusion, long-term clinical follow-up may be needed to detect any recurrence of MCST, irrespective of familial adenomatous polyposis.