Melanoma in situ involving an epidermal inclusion (infundibular) cyst.

Epidermal inclusion (infundibular) cysts are common tumors encountered in the practice of dermatology and dermatopathology. Although benign, numerous pathological processes, including benign and malignant tumors, inflammatory dermatoses, and certain infectious entities, have been reported to occur within the epithelial lining of infundibular cysts. We report a rare case of malignant melanoma in situ involving the epithelium of an epidermal inclusion cyst in contiguity with an adjacent malignant melanoma.