A 49-year-old woman comes to the office for evaluation of abnormal uterine bleeding. The patient has had irregular menses for the past 2 years, but now she has been bleeding daily for 2 weeks. She also has had increased abdominal bloating and pressure but no constipation or diarrhea. Medical history includes early-stage breast cancer diagnosed at age 45 and managed with tamoxifen for the past 4 years. On examination, there is a midline, immobile pelvic mass at the level of the umbilicus. The patient undergoes hysterectomy with bilateral salpingo-oophorectomy. The final pathology report notes nuclear atypia and numerous mitoses in the affected portion of the myometrium. Which of the following is the most likely diagnosis?
Uterine sarcoma | |
Risk |
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Clinical features |
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Histopathology |
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This patient with abnormal uterine bleeding and bulk symptoms (eg, bloating, pelvic pressure) had a midline pelvic mass similar to that caused by uterine leiomyomas (ie, fibroids). However, uterine fibroids tend to regress rather than enlarge as patients approach menopause (median age 51). In this patient, who was increasingly symptomatic and at increased risk due to tamoxifen use, the most concerning potential diagnosis is uterine sarcoma, a rare but aggressive malignant tumor arising from the uterine myometrium or endometrial connective tissue.
Because uterine sarcomas and leiomyomas often have overlapping clinical presentations and imaging findings, microscopic evaluation is required to differentiate between the two:
Leiomyomas (uterine fibroids) are benign tumors of the uterine myometrium caused by monoclonal proliferation of myocytes and fibroblasts. Therefore, microscopy shows no nuclear atypia and a minimal number of mitotic figures (Choice D).
In contrast, uterine sarcomas are rapidly progressive malignant tumors. Therefore, microscopy shows myocytes and/or endometrial stromal cells with nuclear atypia, abundant mitoses, and areas of necrosis.
Treatment for uterine sarcoma is hysterectomy followed in some cases with chemotherapy and/or pelvic radiation.
(Choice A) Adenomyosis, the invagination of endometrial tissue into the myometrium, commonly presents with heavy menstrual bleeding and an enlarged uterus due to increased endometrial surface area. However, microscopy typically reveals endometrial glands embedded in the myometrium.
(Choice B) Cervical cancer classically presents with abnormal vaginal bleeding (eg, postcoital bleeding). Although cervical cancer can cause nuclear atypia with numerous mitoses, these abnormal changes occur in cervical squamocolumnar epithelial cells, not the myometrium.
(Choice C) Chronic endometritis may present with abnormal uterine bleeding; however, it does not cause a large or immobile pelvic mass. Microscopy typically shows plasma cells within the endometrial stroma, not the myometrium.
Educational objective:
Uterine sarcoma is a rare but aggressive malignant tumor of the uterine myometrium and/or endometrial stromal tissue. Patients typically have clinical features similar to those with uterine leiomyomas (eg, abnormal uterine bleeding, immobile pelvic mass), but uterine sarcoma can be distinguished by microscopy, which typically shows characteristic malignant features such as nuclear atypia, abundant mitoses, and tumor necrosis.