Specification and use of a mouse monoclonal antibody raised against melanosomes for the histopathologic diagnosis of amelanotic malignant melanoma

Abstract

The positive reactivity and specificity of a mouse monoclonal antibody (MoAb) human melanosome‐specific antigen (HMSA) 2 raised against the melanosomal protein with amelanotic malignant melanoma on routine paraffin sections is reported. MoAb HMSA‐2 identified cytoplasmic antigen with the following specifications: (1) a sharp heterogeneous expression in melanoma cells (acral lentiginous melanoma [ALM], 11 of 14; superficial spreading melanoma [SSM], 13 of 14; nodular melanoma [NM], one of three; and lentigo maligna melanoma [LMM], zero of two), whereas a diffuse homogeneous expression in cells of benign pigmented melanocytic nevi; and (2) an intense expression on amelanotic melanoma cells as opposed to a weak or negative expression on highly melanotic cells. The positive reactivity of MoAb HMSA‐2 with amelanotic melanomas was exemplified by two shave‐biopsy specimens of amelanotic subungual and plantar lesions, and by two cases of axillary and cervical amelanotic nodes that were left undiagnosed on routine hematoxylin and eosin (H & E) sections because of lack of melanin pigments. These were found, after diagnosis with MoAb HMSA‐2, to possess the regressed primary lesions (both ALM). Copyright © 1988 American Cancer Society