Abstract:

A 14-year-old male with a history of eosinophilic esophagitis and mast cell activation disorder presented with a rapidly evolving "pimple" that had grown to a size of 3x3 centimeters. The nodule was exophytic and bright red with hemorrhagic crust. The clinical differential was an acneiform lesion/folliculitis versus a pyogenic granuloma. Histologic sections of an excisional biopsy demonstrated epidermal acanthosis with overlying orthokeratosis. The dermis was filled with a sheet-like proliferation of both ovoid and spindled cells with prominent eosinophilic granular cytoplasm and vesicular nuclei with prominent nucleoli. Immunohistochemical stains for HMB-45, S-100, CD45, CD117, CD163, Desmin and Cytokeratin were performed and were negative. CD68 highlighted rare cytoplasmic positivity. Immunohistochemical stains for ALK demonstrated diffuse cytoplasmic positivity within tumor cells. These findings were consistent with a diagnosis of a non-neural granular cell tumor (NNGCT), also known as primitive polypoid granular cell tumor. NNGCT is a rare neoplasm first described by LeBoit et al in 1991. These tumors are immunohistochemically distinct from the conventional granular cell tumor. Most notably, NNGCT are S-100 and SOX-10 negative. Recent studies have shown ALK gene fusions to be enriched in this subtype of tumor, and the presence of diffuse ALK positivity aided the diagnosis in this instance. To date, there have been roughly forty cases described in the literature, and typically, NNGCT are characterized as slow growing indolent tumors. To the authors' knowledge, this is the first case of a rapidly evolving NNGCT, clinically mimicking a pyogenic granuloma.

Financial Disclosure:
No current or relevant financial relationships exist.

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Merrick Kozak, MD