Pyoderma Gangrenosum with Pseudoepitheliomatous Hyperplasia Histopathologically Misdiagnosed as Squamous Cell Carcinoma: A Case Report and Brief Literature Review.

Pseudoepitheliomatous hyperplasia (PEH), a rare histopathological manifestation of pyoderma gangrenosum (PG), closely resembles squamous cell carcinoma (SCC) and leads to misdiagnosis, yet relevant reported cases remain limited. We report a 71-year-old female who developed abdominal pain and persistent fever after tooth extraction. Subsequent erythema, ulcerative necrotic lesions occurred on her left dorsal hand following frequent intravenous infusion, and lesions paradoxically expanded after surgical debridement. Initial biopsy and pathological consultation suggested SCC with positive surgical margins. However, the rapid progression of the lesion was inconsistent with SCC. Finally, a repeat biopsy confirmed diffuse neutrophilic infiltration with benign PEH, confirming the diagnosis of PG. The patient received systemic immunosuppressive therapy with oral prednisolone and sulfasalazine, systemic symptoms resolved and cutaneous lesions healed completely without recurrence during follow-up. This case highlights that while PEH is a known variant of PG, its potential to mimic malignancy remains a significant diagnostic pitfall that is often underrecognized in clinical practice. Comprehensive evaluation of distinctive clinical manifestations and a repeat biopsy when necessary are crucial for confirming PG, so as to prevent diagnostic delay and unnecessary surgical interventions.