Vegetative Pyoderma Gangrenosum Mimicking Squamous Cell Carcinoma: A Poorly Recognized Diagnostic Challenge

Area of Science:

• Dermatology
• Oncology
• Pathology

Background:

• Pyoderma gangrenosum (PG) is a rare neutrophilic dermatosis with non-specific diagnostic features.
• Differentiating pseudoepitheliomatous hyperplasia (PEH) from squamous cell carcinoma (SCC) presents histopathologic challenges.
• The association between PEH and PG is infrequently recognized, leading to rare instances of PG mimicking SCC.

Purpose of the Study:

• To report a rare case of vegetative pyoderma gangrenosum (PG) with pseudoepitheliomatous hyperplasia (PEH) that was initially misdiagnosed as squamous cell carcinoma (SCC).
• To emphasize the diagnostic difficulties arising from PEH in the context of PG, potentially leading to misidentification as SCC.
• To underscore the critical need for integrated clinical and histopathologic assessment in the prompt diagnosis of PG.

Main Methods:

• Case report of a 78-year-old woman with a 3-month history of an ulcerated, exophytic mass on the lower leg.
• Initial incisional biopsy revealed PEH and neutrophilic microabscesses, raising suspicion for SCC.
• Diagnosis was revised to vegetative PG with PEH after multidisciplinary review at a cutaneous oncology tumor board, correlating clinical and histopathologic findings.

Main Results:

• The patient presented with clinical and histopathologic features initially suggestive of SCC with PEH.
• Histopathologic examination showed PEH and neutrophilic microabscesses, complicating the differential diagnosis.
• A final diagnosis of vegetative PG with associated PEH was established, highlighting the mimicry of SCC.

Conclusions:

• Pseudoepitheliomatous hyperplasia (PEH) can be a confounding histopathologic feature in pyoderma gangrenosum (PG), mimicking squamous cell carcinoma (SCC).
• Accurate diagnosis of PG requires careful correlation of clinical presentation with histopathologic findings to avoid misdiagnosis.
• Prompt diagnosis of PG is crucial to prevent diagnostic delays and the initiation of unnecessary treatments or surgeries.