Pigmented Dermatofibrosarcoma Protuberans: Description of a pediatric case.

INTRODUCTION

Bednar tumor is a rare low-grade sarcoma considered the pigmented variant of dermatofibrosarco ma protuberans (DFSP).

OBJECTIVE

To describe the clinical and histopathological characteristics, treatment and evolution of this rare neoplasm.

CLINICAL CASE: A 9-year old female presented with a 2-year history of an indurated, asymptomatic papule on the back of her fourth left toe. The incisio nal biopsy was compatible with pigmented DFSP. The immunohistochemical study showed intense positivity for CD34 throughout the lesion, with negative factor XIIIa. We complemented the study with molecular cytogenetics (FISH) for PDGFB gene (22q13.1) which showed an abnormal pattern in tumor cells, but not in the melanocytes or the peritumoral skin. Delayed Mohs surgery and skin substitute dressing were performed without neoplastic recurrence at 5 years of follow up. Conclu sion: Pigmented DFSP is a low-grade sarcoma that is very rare in pediatric patients. The classical and pigmented variants should be suspected in the presence of a single papulonodular lesion of slow and progressive growth, with presence of spindle cells with storiform pattern in the biopsy and positive immunohistochemical study for CD34. It is an entity with good prognosis, with little risk of recurren ce and metastasis, if complete excision is achieved.