Congenital sacrococcygeal rhabdomyosarcoma.

Rhabdomyosarcoma (RMS) is one of the common malignant soft-tissue sarcomas affecting children. It originates from the embryonic mesenchyme precursor of striated muscle and is frequently seen in the head-and-neck region, genitourinary system and extremities. Occasionally, it arises from the retroperitoneum, biliary tract and abdomen and is rarely seen in the sacrococcygeal area. A 4-month-male child presented with a nodule over the sacrum. Based on histopathology and immunohistochemical marker studies, a final diagnosis of RMS was rendered. There was no evidence of any teratomatous elements.