title: The histiocytic marker PG-M1 is helpful in differentiating histiocytes and histiocytic tumors from melanomas.
abstract: Previous studies have shown that immunohistochemical stains for histiocytes are immunoreactive for melanomas. Accordingly, their value in differentiating histiocytes and histiocytic lesions from melanomas was questioned. PG-M1, the most specific histiocytic marker, was not evaluated in these studies. Our aims were to assess the reactivity of PG-M1 with a series of primary cutaneous and metastatic melanomas and to establish the potential usefulness of this antibody in the differentiation between histiocytes and histiocytic tumors and melanomas. PG-M1 staining was performed in 50 primary cutaneous and metastatic melanomas. For comparison, additional sections were stained with KP-1 and lysozyme (commonly used as histiocytic markers) and with S-100 and HMB-45 (commonly used as melanoma markers). The intensity (1+, 2+) and extent (1+ to 4+) were recorded semiquantitatively. PG-M1 stained weakly (1+) and focally (2+) only four cases of melanoma (8%). In contrast, histiocytes were strongly reactive for PG-M1 in all cases, being readily differentiated from melanoma cells including the positive cases. KP-1 stained melanoma cells in 44 cases (88%), lysozyme in 11 cases (22%), S-100 in 50 cases (100%), and HMB-45 in 48 cases (96%). No changes were found after restaining of selected KP-1 and lysozyme positive melanomas using an endogenous avidin/biotin blocking kit. PG-M1 is helpful in discriminating histiocytes and histiocytic lesions from melanoma cells. We recommend its inclusion in any antibody panel put together to distinguish between them.
authors.affiliation: Hillel-Yaffe Medical Center, Hadera, Israel. groisman@hillel-yaffe.health.gov.il
authors.forename: Gabriel M
authors.initials: GM
authors.lastname: Groisman
authors.forename: Mary
authors.initials: M
authors.lastname: Amar
authors.forename: Ion
authors.initials: I
authors.lastname: Schäfer
mesh_terms: D015703:Antigens, CD / Q000378:metabolism*; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000378:metabolism; D003937:Diagnosis, Differential; D006644:Histiocytes / Q000276:immunology* / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008545:Melanoma / Q000175:diagnosis* / Q000276:immunology* / Q000473:pathology / Q000556:secondary; D009113:Muramidase / Q000378:metabolism; D018218:Neoplasms, Fibrous Tissue / Q000175:diagnosis* / Q000276:immunology* / Q000473:pathology; D012878:Skin Neoplasms / Q000175:diagnosis* / Q000276:immunology* / Q000473:pathology; D000097382:CD68 Molecule
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D014408:Biomarkers, Tumor; D009113:Muramidase; C067980:CD68 antigen, human; D000097382:CD68 Molecule