Dermatofibrosarcoma protuberans in the breast of a 2-year-old girl.

Dermatofibrosarcoma protuberans (DFSP) is a low-grade dermal and subcutaneous spindle cell neoplasm that most commonly occurs in the extremities and trunk of adults. It is rare in children and infants, and only few cases are reported as congenital. A 2-year-old girl presented with a rapidly enlarging left breast mass. The histology of the excised mass revealed a moderately cellular spindle cell tumor with large hypercellular fibrosarcoma-like areas, few myxoid areas, and other areas with multinucleated giant cells. By immunohistochemistry, the tumor cells were focally positive for CD34 and were negative in the fibrosarcomatous areas. The diagnosis of DFSP was confirmed by demonstrating an unbalanced translocation der(22)t(17;22)(q21.3;q13.1) by conventional cytogenetic and fluorescence in situ hybridization analyses. Positive immunoreactivity with PDGFR-beta antibody indicated constitutional activation of PDGF receptor and provided an alternate indirect method of confirming the presence of dysregulated PDGF gene involved in this translocation. Although DFSP has been described in the adult female breast, this is the first such case in the breast of a 2-year-old girl. Dermatofibrosarcoma protuberans should be considered in the differential diagnosis of subcutaneous/dermal spindle cell tumors in children regardless of the site. CD 34 immunostaining should not be relied on, as it may be negative in fibrosarcomatous areas. Confirmation of the diagnosis in unusual sites requires identification of the characteristic t(17;22) chromosomal translocation.