Pleural metastases exhibiting high-grade endometrial stromal sarcoma with both rearrangement of the YWHAE gene and BCORL1 alteration

Endometrial stromal sarcoma (ESS) is a rare malignant neoplasm of endometrial stroma. High-grade ESS (HGESS) is aggressive and commonly relapses after surgical and neoadjuvant therapy. The abdomen and pelvis are common sites of metastasis, however, distant metastases to the liver, lung, vertebrae, and brain have been reported. We encountered a 49-year-old female who presented with shortness of breath and was subsequently found to have a left pleural effusion and multiple pleural masses. Hysterectomy and bilateral salpingo-oophorectomy performed three years ago revealed an intramural 7 cm uterine mass with a serpiginous growth pattern and lymphovascular invasion. The tumor cells, plump to spindled in morphology, were positive for cyclin D1, focally positive for CD10, and negative for desmin, AE1/AE3, and CAM5.2. FISH studies showed rearrangement of the YWHAE gene (17p13.3) and molecular assay revealed BCORL1 alteration C1065 (3195C > A). The findings supported the diagnosis of HGESS for which the patient underwent post-operative chemotherapy. Biopsy of the current pleural lesion revealed a nonspecific malignant spindle cell neoplasm with a nonspecific immunohistochemical phenotype. However, FISH studies further revealed rearrangement of the YWHAE gene (17p13.3). The findings support the diagnosis of metastatic HGESS. HGESS, a rare tumor with a nonspecific immunostain profile, can metastasize to unusual body sites including the pleura, as in our case. To our knowledge, this is the first case of HGESS with both the YWHAE gene rearrangement and BCORL1 alteration presenting in the setting of pleural effusion and pleural metastases. Tumor cells displaying spindle cell morphology, a nonspecific finding, raise broad differential diagnoses, including HGESS, an important consideration to keep in mind for women with or without a history of uterine neoplasm