Sclerosing stromal tumor of the ovary in a 4-year-old girl with characteristics of an ovarian signet-ring stromal tumor

Ovarian sclerosing stromal tumor (OSST) is an extremely rare neoplasm that primarily affects young women. Signet-ring stromal tumor is another rare non-functioning benign ovarian stromal neoplasm. We report a case of a right OSST with prominent characteristics of signet-ring stromal tumor in a 4-year-old girl with symptoms of premature thelarche. We describe the clinical, histopathological, and immunohistochemical findings and review the literature. To our knowledge, the 4-year-old patient presented here is the youngest case of OSST reported in premenarchal children. The presence of non-mucin/non-lipid obvious signet-ring-like cells in this case suggests a possible relationship between OSST and signet-ring stromal tumor of the ovary.