Rhabdomyoblasts in Pediatric Tumors: A Review with Emphasis on their Diagnostic Utility

Abstract

Rhabdomyosarcoma is a soft tissue pediatric sarcoma composed of cells which show morphological, immunohistochemical and ultrastructural evidence of skeletal muscle differentiation. To date four major subtypes have been recognized: embryonal, alveolar, spindle cell/sclerosing and pleomorphic. All these subtypes are defi ned, at least in part, by the presence of rhabdomyoblasts, i.e. cells with variable shape, densely eosinophilic cytoplasm with occasional cytoplasmic cross-striations and eccentric round nuclei. It must be remembered, however, that several benign and malignant pediatric tumours other than rhabdomyosarcoma may exhibit rhabdomyoblaststic and skeletal muscle differentiation. This review focuses on the most common malignant pediatric neoplasm that may exhibit rhabdomyoblastic differentiation, with an emphasis on the most important clinicopathological and differential diagnostic considerations.