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Case Reports

Abstract

Dermatofibrosarcoma Protuberans (DFSP) is an uncommon soft tissue sarcoma that arises from the dermis and most commonly occurs on the trunk and proximal extremities. It is a slow-growing tumor that typically presents as a plaque-like lesion. DFSP is characterized by uniform, CD34+ spindle cells arranged in a storiform pattern, often infiltrating the subcutis in a honeycomb pattern. Occasional cases have prominent myxoid stroma with a loss of the classic storiform pattern.  We report a case of a 42-year-old female who presented with right suprapubic pain and a rapidly growing mass near the suprapubic area adjacent to the mons pubis. Initially presumed to be a cyst, the patient’s primary care physician attempted drainage; however, the lesion persisted. Clinical differential diagnoses included pyogenic granuloma and amelanotic melanoma.The lesion measured 2.5 × 2.7 cm. Biopsy revealed uniform spindle-to-stellate-shaped cells evenly distributed in an abundant myxoid stroma with a prominent capillary vasculature. No significant pleomorphism or mitotic activity was identified. Immunohistochemical staining was negative for CD34, SOX-10, S100 protein, and SMA. Further immunohistochemical work-up showed negative for estrogen receptor, desmin, MyoD1, DUX4, and ALK. Despite CD34 negativity, myxoid DFSP remained a strong consideration. Next-generation sequencing (NGS) revealed a COL1A1::PDGFB fusion, confirming the diagnosis.This case highlights the importance of recognizing the histologic features of myxoid DFSP and molecular testing in establishing the diagnosis in problematic cases, particularly in atypical presentations with CD34 negativity.