Bednar Tumor: A Rare Variant of Dermatofibrosarcoma Protuberans.

Dermatofibrosarcoma protuberans (DFSP) is a rare dermal sarcoma of intermediate malignancy characterized by locally aggressive behavior and a low metastatic potential. The classic form typically presents as a slow-growing protuberant tumor involving the trunk or proximal extremities; however, several uncommon variants have been described. We report the case of a 32-year-old woman who presented with a long-standing pigmented lesion on the shoulder that had been present since childhood and showed progressive changes over the preceding six months. Clinically, the lesion evolved into an oval-shaped neoplasm with erythematous and brown pigmentation, a smooth surface, and an infiltrative consistency. Based on the clinical features, a diagnosis of DFSP was suspected, with particular consideration given to its rare pigmented variant, known as Bednar tumor. Histopathological examination and immunohistochemical analysis were performed to confirm the diagnosis and guide management. Although Bednar tumor exhibits distinctive histologic features due to the presence of melanin-producing dendritic cells, its biological behavior and prognosis are similar to those of conventional DFSP. Notably, only three cases of DFSP have been diagnosed over a 13-year period at a tertiary dermatology referral center in western Mexico, underscoring the rarity of this entity and the importance of clinical awareness for timely diagnosis and appropriate treatment.