Below the Belt: A Case of an Atypical, Large Perineal Lump.

Perineal lumps can cause significant distress and functional impairment, often presenting diagnostic challenges due to a wide range of differential diagnoses, including abscesses, median raphe cysts, benign teratomas, and other rare soft-tissue lesions. While epidermoid cysts are common, benign cutaneous lesions frequently encountered on the neck, trunk, or face, their occurrence in the perineum is a rarity. When present, they are often secondary to mechanical pressure, minor trauma, or previous surgical interventions. A 30-year-old gentleman presented with an insidiously growing, painless perineal swelling measuring approximately 8 x 8 x 6 cm that significantly interfered with his ability to sit and perform daily activities. Clinical examination revealed a superficial, well-defined, cystic, and mobile mass with no signs of inflammation, toxemia, or gastrointestinal involvement. An MRI was utilized to evaluate the mass, demonstrating a well-marginated midline lesion clearly separated from the testes, anal sphincters, and surrounding musculature. Based on these findings, the patient underwent complete surgical excision of the mass via an elliptical vertical incision. The mass was successfully excised in toto, with careful dissection ensuring completeness of removal of the cyst wall. Macroscopic examination of the resected tissue's cut section revealed thick, inspissated sebaceous material. Subsequent histopathological evaluation demonstrated a dermal-based cyst lined by stratified squamous epithelium with an intact granular layer and lamellated keratin flakes with absent adnexal structures, definitively confirming an epidermal inclusion cyst. Although infrequent in the perineum, an epidermal inclusion cyst should be amongst the differential diagnoses of slow-growing, atypical perineal swellings. Advanced imaging techniques like MRI are valuable for preoperative planning, but complete surgical extirpation remains the definitive standard of care. Removing the entire cyst wall successfully relieves patient discomfort, provides necessary tissue for histopathological diagnosis, and effectively prevents future recurrences.