Background: The rhabdoid phenotype is characterized by large epithelioid cells with abundant eosinophilic cytoplasm and paranuclear inclusions of intermediate filaments. Although originally described in tumors from pediatric kidneys, the rhabdoid phenotype has since been described in a variety of patient ages and extrarenal sites. Extraordinarily, the rhabdoid phenotype has emerged in cutaneous neoplasms, either as a pure extrarenal rhabdoid tumor or a composite phenotype coupled with another malignancy. Regardless of the clinical setting, the rhabdoid phenotype is uniformly associated with aggressive biological behavior. We report the findings from a rare and very aggressive primary extrarenal rhabdoid tumor of the skin with myogenic differentiation. Case report: A 53-year-old woman presented with an ulcerated nodule on her right medial calf and ipsilateral inguinal lymphadenopathy. Histological examination of the skin nodule as well as cytologic examination of a lymph node disclosed the characteristic rhabdoid phenotype. Electron microscopy demonstrated paranuclear globules of intermediate filaments; special stains suggested an underlying myogenic histogenesis. The patient was aggressively treated with chemotherapy but ultimately died of her disease 8 months after presentation. Conclusions: The rhabdoid phenotype is rarely seen in cutaneous neoplasms, but when present, portends a poor prognosis adding particular importance to its recognition.
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