Track: Clinical Studies

Abstract:

Diagnosing pyoderma gangrenosum (PG) remains challenging because its clinical presentation is highly variable, it can resemble several other disorders, and it is often linked to a range of systemic diseases. The condition lacks specific histopathologic features, making definitive identification difficult. Histologically, PG often demonstrates neutrophilic inflammation; however, this finding is nonspecific and may differ depending on the clinical subtype, stage, and timing of the biopsy. These factors contribute to frequent diagnostic delays and errors. Pseudoepitheliomatous hyperplasia (PEH) is a benign proliferation of the epidermis and adnexal epithelium that can mimic squamous cell carcinoma (SCC) both clinically and histologically. While PEH occurs in a variety of conditions, its association with PG is exceptionally uncommon. We report a rare case of PG with extensive PEH that closely simulated SCC, posing a considerable diagnostic challenge. Including our case, only six instances of PG accompanied by PEH mimicking SCC have been reported. Histopathologic examination revealed irregular epidermal and adnexal hyperplasia, an adnexal-centered epithelial proliferation, preservation of eccrine ducts, absence of significant cytologic atypia, and low mitotic activity, features that favor PG with Associated PEH over SCC. Awareness of this rare association and recognition of these key microscopic features are crucial to avoid misdiagnosis and unnecessary aggressive management. This report and literature review represent the first effort to outline diagnostic criteria for distinguishing PG with PEH from SCC, aiming to reduce diagnostic confusion and improve patient outcomes.

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Guilherme Barreiro