RESUMEN
Fibrosarcoma is rare in pediatric age group. Its diagnosis in infants may be difficult clinically and histologically. A twenty-day infant presented with a rapidly growing mass in the right forearm. Histologically a gray white fleshy mass was seen occupying the entire forearm and distal arm. The tumor showed sheets of closely packed spindle cells with minimal pleomorphism. The cells were positive for vimentin, negative jor smooth muscle actin, desmin and S-100. The diagnosis of congenital fibrosarcoma was made. Most cases of infantile fibrosarcomas present in the first year of life and although they have an alarming presentation, in children they have a much better prognosis as compared to adults. Diagnosis can be made on histology with immunohistochemistry.