title: Malignant melanoma within an intradermal nevus.
abstract: We describe a case of malignant "dermal" melanoma that arose within a preexisting intradermal nevus. Clinically, the lesion had recently enlarged. Histologically, two patterns were noted. One was an intradermal nevus in the upper portion of the dermis; the other was a deeper nodule composed of malignant neoplastic cells that extended into the reticular dermis. No melanocytic epidermal junctional activity was noted. Despite careful clinical investigation, no alternative primary source was found. Neoplastic transformation of the intradermal nevus without junctional activity is our proposed interpretation of the lesion's histology. Immunohistochemical stains demonstrated that the deeper dermal neoplastic cells were positive for both HMB-45 and PCNA, whereas the superficial nevoid-appearing cells were negative; these findings support our postulate that this melanoma arose within an intradermal nevus. It is important to distinguish this neoplasm from other diagnostic possibilities, including a metastatic lesion originating from another site.
authors.affiliation: Department of Surgical Pathology, Teikyo University School of Medicine, Ichihara Hospital, Chiba, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Tajima
authors.forename: T
authors.initials: T
authors.lastname: Nakajima
authors.forename: I
authors.initials: I
authors.lastname: Sugano
authors.forename: K
authors.initials: K
authors.lastname: Nagao
authors.forename: Y
authors.initials: Y
authors.lastname: Kondo
mesh_terms: D000368:Aged; D000951:Antigens, Neoplasm; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008545:Melanoma / Q000737:chemistry / Q000473:pathology*; D058950:Melanoma-Specific Antigens; D009363:Neoplasm Proteins / Q000032:analysis; D009378:Neoplasms, Multiple Primary / Q000737:chemistry / Q000473:pathology*; D018330:Nevus, Intradermal / Q000737:chemistry / Q000473:pathology*; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D009418:S100 Proteins / Q000032:analysis; D012878:Skin Neoplasms / Q000737:chemistry / Q000473:pathology*
chemical_list: D000951:Antigens, Neoplasm; D058950:Melanoma-Specific Antigens; D009363:Neoplasm Proteins; D018809:Proliferating Cell Nuclear Antigen; D009418:S100 Proteins