July 2020 Case

This is a 55-year-old female with no significant PMH who presented with postmenopausal bleeding and bilateral sharp shooting pain in the pelvis. She underwent an endometrial biopsy, which demonstrated a müllerian mesenchymal neoplasm that could not be further classified based on histologic findings and immunostains. An NGS panel for sarcoma gene fusions was negative for gene rearrangements. Subsequent imaging revealed an enhancing mass centrally within the uterus extending into the endocervix. The patient underwent a total laparoscopic hysterectomy and bilateral salpingo-oophorectomy. On gross exam 5.0 x 3.0 x 2.5 cm tumor was found in the left side of the uterine corpus and did not involve the cervix.

Figure 1: A well-circumscribed polypoid, tan-yellow, soft tumor with no necrosis

Figure 2. (H&E, 40x and 200x magnifications): Solid sheets of spindle cells with round to spindle nuclei, open chromatin and small nucleoli

Figure 3. (H&E, 40x & 200x magnifications): Retiform architecture of epithelioid cells with hyaline material resembling a sex cord-like structure.

Figure 4: Immunohistochemical stains, sex cord markers

Figure 5. Additional immunohistochemical stains

Uterine tumor resembling ovarian sex cord tumor (UTROSCT)

UTROSCT is a rare uterine mesenchymal neoplasm that tends to occur in middle-aged women. 

The tumor consists of sex cord-like and mesenchymal differentiation with various possible components, including Sertoli-like tubules, nested granulosa-like architecture, retiform growth, lipidized cells, Leydig-like cells, stromal cells with infiltrative growth, and solid sheets of smooth muscle-like cells. Occasional vascular invasion and necrosis can be seen. Mitotic activity is low, and cytological atypia is minimal. 

UTROSCT expresses a variable immunoprofile with possible positive or negative staining for any of the commonly used sex cord markers, including inhibin, calretinin, SF1, WT1, and FOXL2. Co-expression of epithelial and muscle markers is common. UTROSCT is also typically positive for CD10 and less commonly positive for ER and PR. The differential diagnosis includes endometrial stromal tumor with sex cord-like differentiation, endometrial carcinoma with sex cord-like differentiation, adenosarcoma with extensive sex cord-like differentiation, and mesonephric adenocarcinoma. These entities can be distinguished based on a combination of histopathologic features, immunophenotyping, and molecular analysis. 

Fusion genes found in UTROSCT include ESR1-NCOA3 (41%), GREB1-NCOA1 (18%), ESR1-NCOA2 (14%), and GREB1-NCOA2 (5%). Some adenosarcomas with extensive sex cord-like differentiation may also have a NCOA 2/3 gene fusion, which can render distinguishing between this entity and UTROSCT quite challenging. UTROSCT lacks FOXL2 and DICER1 mutations, which are found in granulosa cell tumors and Sertoli Leydig cell tumors of the ovary, respectively. UTROSCT also lacks JAZF1 and PHF1 rearrangements, which is helpful in differentiating UTROSCT from low grade endometrial stromal sarcoma. 

UTROSCT has indolent behavior in most cases. Uncommonly, these tumors may behave aggressively and infiltrate the myometrium or through the serosa. Distant metastasis is rare but has been reported.

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