Diagnostic Challenge of Recurrent Dermatofibrosarcoma Protuberans Mimicking Other Spindle Cell Lesions: Importance of Immunohistochemistry in Diagnosis.

Dermatofibrosarcoma protuberans (DFSP) is an uncommon, low-grade cutaneous sarcoma with fibroblastic differentiation. It typically shows slow progression but is locally aggressive and has a tendency for recurrence if not adequately excised. Although metastasis is rare, DFSP often infiltrates deeper tissues and may closely resemble other benign spindle cell lesions both clinically and on routine histology, creating diagnostic difficulty. Immunohistochemistry plays a crucial supportive role in assisting with the diagnostic workup. We report a 54-year-old male who presented with a painless swelling over the right scapular region. The lesion was initially diagnosed in 2019 as a benign spindle cell lesion on core needle biopsy and excision biopsy. He developed a recurrence at the same site in 2022, which was again reported as a spindle cell lesion with differentials including fibromatosis, DFSP. In 2024, the patient returned with a progressively enlarging mass at the same location, following which a wide local excision was performed. Histopathological examination showed features consistent with DFSP and immunohistochemistry revealed diffuse CD34 positivity. The tumor was found to infiltrate skeletal muscle and extend up to the deep surgical margin. This case highlights the diagnostic pitfalls of DFSP, particularly when it presents as a recurrent spindle cell lesion and mimics benign entities such as fibromatosis. Careful histopathological evaluation supported by immunohistochemistry is essential for timely diagnosis and appropriate surgical management.