title: Rhabdomyosarcoma of the common bile duct in an adult.
abstract: Rhabdomyosarcoma (RMS) of the hepatobiliary system is extremely rare in adults. To our knowledge only three cases have been reported in the literature, all involving the gallbladder. The present case concerns a 40-year-old woman who presented with epigastric pain and obstructive jaundice and was found to have a fusiform, submucosal neoplasm in the common bile duct. Histologically, the tumor presented a diagnostic problem due to a predominant sclerotic growth pattern suggesting an epithelial tumor. Extensive sampling revealed a focal alveolar growth pattern with rhabdomyoblasts, although cross striations were not seen. Electron microscopy failed to demonstrate the characteristic thick myofilaments and/or Z-band material. The diagnosis was supported by strongly positive immunohistochemical staining for myoglobin and desmin; the keratin stain was negative. A subsequent supraclavicular metastasis showed the typical histology of an alveolar RMS. The histologic features of the primary tumor suggest that RMS in this location may be underrecognized due to regional similarities to either primary or metastatic infiltrating carcinomas.
mesh_terms: D000328:Adult; D000368:Aged; D003138:Common Bile Duct Neoplasms / Q000032:analysis / Q000473:pathology*; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D012208:Rhabdomyosarcoma / Q000032:analysis / Q000473:pathology*