A 20-year-old woman with no significant past medical history presented with 14.5 cm ovarian mass. She underwent an oophorectomy. Grossly, the ovarian mass shows yellow to white, firm cut surface. Representative sections of the ovarian mass depicted below, along with the selected immunohistochemical stains.
The correct answer is ...
Sclerosing stromal tumor.
Sclerosing stromal tumor are uncommon ovarian tumors that occur generally in young woman and girls with a mean age of 29 years. These tumors range in size from 1.5 cm to 19 cm. Gross examination, they are generally well circumscribed and have a yellow to white solid cut surface. They often show areas of central edema with cystic degeneration.
Microscopically, these tumors have pseudolobular appearance, with alternating hypocellular myxoid edematous areas and cellular areas with collagenized zones. They typically show abundant, thin-walled, dilated vessels with prominent branching, often with a hemangiopericytoma-like appearance. In the cellular areas, spindle-shaped cells and polygonal luteinized cells are present. The luteinized cells show eosinophilic to clear vacuolated cytoplasm, round nuclei, and prominent nucleoli. Occasionally the luteinized cells may have signet ring cell appearance, especially during pregnancy. Scant spindle cells with pale cytoplasm and elongated nuclei are also usually present. Mitotic activity is generally low.
Sclerosing stromal tumor are usually positive for sex cord markers, such as inhibin, calretinin, or SF1 but are negative for cytokeratin and EMA. Recent studies have shown that a subset of these cases shows TFE3 expression.
The differential diagnosis includes other sex cord stromal tumors including fibrothecoma, microcystic stromal tumor, and adult granulosa cell tumor. Some tumors that demonstrate vacuolated cytoplasm may mimic metastatic signet ring adenocarcinoma. Fibrothecoma typically occur in peri- or postmenopausal woman with abnormal bleeding. Grossly the tumor demonstrates a uniform white cut surface. They typically lack the luteinized cells present in sclerosing stromal tumor and do not show the characteristic hemangiopericytoma like vasculature.
Microcystic stromal tumor is a benign ovarian tumor with striking microcystic growth. These tumors show admixture of microcysts, solid areas, and collagenous bands. They can often show bizarre nuclei in up to 60% of the cases. These tumors are usually very focally and weakly positive for inhibin and calretinin.
The adult granulosa cell tumor can show variety of growth patterns and should be considered in differential diagnosis for sclerosing stromal tumor. The adult granulosa cell tumor shows FOXL2 mutation in approximately 90% of the cases and can help in the diagnosis. Metastatic adenocarcinoma can be excluded by immunohistochemical studies (EMA positive and with specific epithelial markers such as CDX2, CK20, MOC31, as well as mucin stains).
Raima Memon, M.B.B.S.
Fellow, Surgical Pathology
Amy Clayton, M.D.
Consultant, Anatomic Pathology
Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Science