Epithelioid Clear Cell Smooth Muscle Tumor of the Ovary Presenting as a Mural Nodule in an Endometrioid Adenocarcinoma With Clear Cell Changes

Abstract

Although rare, mural nodules in cystic ovarian neoplasms are a well-recognized phenomenon. They encompass sarcoma, sarcoma-like nodules, anaplastic carcinoma, leiomyomatous, and mixed nodules. We present a case of a 69-year-old woman with a large stage IA endometrioid adenocarcinoma with clear cell change arising in an endometrioid adenofibroma. Histologic examination of a 3-cm mural nodule detected during gross preparation of the resection specimen showed a predominantly epithelioid clear cell smooth muscle neoplasm with abundant cytoplasmic glycogen. The histomorphology was very reminiscent of pulmonary "sugar tumor" or PEComa. Immunohistochemical investigation showed strong expression of α-smooth muscle actin and desmin. Tumor cells did not stain for cytokeratins, HMB45, and other lineage-specific markers. The patient died of metastatic adenocarcinoma 10 months later. To our knowledge, this case represents the first report of an ovarian epithelioid smooth muscle tumor presenting in this particular setting. The presence of prominent clear cell changes in both the neoplasms is unique.