Pigmented Epidermoid Cyst: A Report of Two Cases

Epidermoid cysts are benign cystic lesions of the hair follicular infundibulum. Commonly found in hair-bearing regions of the body, these lesions frequently occur among young adults. Epidermoid cysts can occasionally be pigmented because of the presence of melanin. This pigmentation is observed in both intact cysts and cysts that have ruptured, showing adjacent foreign body giant cell reaction and macrophage infiltration. Published literature documents that pigmentation in epidermoid cysts is more common among individuals with deeply pigmented skin. The nature of the pigment can be confirmed through special stains or immunohistochemical analysis, which highlights melanocyte proliferation in the basal layer. Presented below are two cases of pigmented epidermoid cysts diagnosed by the authors at their institution. The first patient was a 32-year-old male who presented with complaints of swelling on the extensor aspect of his left forearm. The second patient was a 14-year-old girl with complaints of swelling on her scalp. Both patients underwent wide local excision of the lesions, and histological examination revealed epidermoid cysts containing sheets of pigment-laden macrophages and multinucleated giant cells adjacent to a focus of cyst discontinuity. The nature of the pigment was confirmed to be melanin by a melanin bleach reaction, which showed complete removal of the pigment. These two cases are documented due to their unique histology and the potentially common oversight of pigmented epidermoid cysts.