Pleomorphic Epithelioid/Clear Cell Malignant Tumor of the Uterus Exhibiting both Myoid and Melanocytic Differentiation –⁠ Leiomyosarcoma or PEComa? A Case Report and a Review of the Literature

Overview

30-year-old woman admitted for acute abdominal pain with peritoneal signs was immediately operated with findings of hemorrhage in small pelvis. Laparotomy revealed hemorrhagic, friable mass 3 cm in maximum diammeter arising from the uterine horn. The neoplasm broadly invaded myometrium with no evidence of endometrial cavity involvement. Microscopically, the tumor displayed solid mosaic pattern and consisted of large epithelioid cells with ample eosinophilic, finely granular cytoplasm ongoing apparent clear cell change elsewhere. There was marked nuclear irregularity with numerous atypical mitotic figures and multiple bizarre giant elements dispersed throughout the lesion. Unusual complex phenotype included co-expression of vimentin, smooth muscle actin, desmin, HMB45, Melan A, CD10 and EMA. No obvious stigmata of tuberous sclerosis were found and a five months follow-up after chemotherapy indicated no progression of disease. With some uncertainty the tumor was finally rendered as pleomorphic leiomyosarcoma with peculiar melanocytic differentiation. PEComa as an alternative term was coined. Expressed are both difficulty in explaining the histogenesis and ambiguity of the existing terminology of the uterine tumors with mixed myoid and melanocytic phenotype. Reviewed is the literature and discussed is the differential diagnosis.

Key words:
uterus –⁠ angiomyolipoma –⁠ epithelioid/pleomorphic leiomyosarcoma –⁠ melanocytic differentiation –⁠ PEComa