An Uncommon Perianal Mass in a Girl: A Diagnostic Challenge

A 15-year-old female presented with a two-month history of a tender perianal nodule, which was aggravated by sitting or pressure. She denied having any systemic symptoms. Examination revealed a well-defined, erythematous-to-gray nodule measuring 3 × 3 cm, featuring a corrugated surface at the lateral end. Histopathology showed large polygonal cells with abundant granular eosinophilic cytoplasm and small, uniform nuclei. Immunohistochemical staining was strongly positive for S-100 protein and neuron-specific enolase, confirming the diagnosis of a granular cell tumor (GCT). GCT is a rare, usually benign neoplasm of Schwann cell origin, with perianal involvement being extremely uncommon, especially in pediatric patients. Although most cases are asymptomatic, a perianal GCT can cause discomfort and may require surgical excision with sphincter preservation. While malignant transformation is rare, close monitoring is advised. This case highlights the diagnostic challenges of GCT in unusual locations and underscores the importance of histopathology and immunohistochemistry for accurate diagnosis and management.