Infantile fibrosarcoma: a clinicopathological and molecular study of five cases

We report 5 cases of infantile fibrosarcoma (4 boys and I girt) whose avera ge age was 5, 7 months (range 0 days to 14 months). The tumor was congenita l in 4 cases, All tumors presented in the extremities (forearm, hand, thigh : I case, lower leg: 2 cases). Treatment was based on surgery (3 cases : a mputation, 2 cases: local excision) with a favorable course in all cases, e ven those with marginal excision (follow-up ranging from 5 to 21 years). Th e lesions were characterized by dense monotonous cells growing in a fascicu lar pattern, with small necrotic areas and scattered lymphocytes. The mitot ic index was high (average 8/10 high-power fields), ETV6-NK3 chimeric RNA w as detected by reverse transcriptase polymerase chain reaction in two cases out four cases from paraffin-embedded tissue blocks. The infantile fibrosa rcoma is a good prognosis tumor characterized by particular histological fe atures and ETV6-NK3 gene fusion.