Congenital Atrophic Dermatofibrosarcoma Protuberans With Rapid Nodular Transformation in an Infant: A Case Report

Dermatofibrosarcoma protuberans (DFSP) is an uncommon soft tissue sarcoma with a high risk of local recurrence, of which the congenital atrophic variant is exceptionally rare and prone to misdiagnosis. We report a case of a 10-month-old male infant with a rapidly enlarging, tender nodule arising within a congenital atrophic plaque on the left lower leg, which histopathologically demonstrated a CD34-positive spindle cell tumor featuring storiform architecture and deep honeycomb infiltration. Notably, fluorescence in situ hybridization (FISH) analysis revealed no evidence of the characteristic PDGFB gene rearrangement, consistent with a molecularly unconfirmed DFSP. This case highlights the critical importance of including DFSP in the differential diagnosis of progressive congenital plaques, supports the biphasic growth model, and underscores the necessity of integrating histopathology with advanced molecular techniques for accurate diagnosis and management, even in the absence of classic molecular markers.