The American journal of surgical pathology
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Am. J. Surg. Pathol. · Sep 2001
Are myogenin and myoD1 expression specific for rhabdomyosarcoma? A study of 150 cases, with emphasis on spindle cell mimics.
Rhabdomyosarcoma (RMS), the most common soft tissue sarcoma of childhood, displays a variety of histologic patterns. Immunohistochemistry is used extensively to distinguish RMS from its mimics. Myogenin and MyoD1, myogenic transcriptional regulatory proteins expressed early in skeletal muscle differentiation, are considered sensitive and specific markers for RMS and are more specific than desmin and muscle-specific actin and more sensitive than myoglobin. ⋯ In contrast to previous studies, rare non-RMS (7 of 107) displayed focal nuclear reactivity, and entrapped atrophic or regenerative skeletal muscle fibers also stained positively. Although these are potential pitfalls in the interpretation of myogenin, careful attention to morphology and other features, to the relative paucity of myogenin-positive nuclei in non-RMS. and to the presence of entrapped muscle fibers should prevent incorrect interpretation. Because the extent of myogenin expression in RMS is much greater than in non-RMS, it is a very useful marker when interpreted in the context of other clinicopathologic data.