Pigmented Epithelioid Melanocytoma (PEM)/Animal Type Melanoma (ATM): Quest for an Origin. Report of One Unusual Case Indicating Follicular Origin and Another Arising in an Intradermal Nevus

The document presented two cases of Pigmented Epithelioid Melanocytoma (PEM)/Animal Type Melanoma (ATM), suggesting different origins for this type of melanocytic tumor. In the first case, a 63-year-old male had a tumor on the scalp with histologic evidence pointing to an origin from the follicular bulge region of a hair follicle. The second case involved a 72-year-old female with a tumor on the upper back that developed from an intradermal nevus. Both cases showed atypical mitotic figures. The study proposed that PEM could originate from stem cells in the follicular bulge or from an intradermal nevus, drawing parallels to the origins of certain cutaneous squamous cell carcinomas. The conclusion was that PEMs might have multiple potential origins, including the bulge region of hair follicles or an intradermal nevus.