title: Altered Morphology and Immunohistochemical Characteristics in Metastatic Malignant Melanoma After Therapy With Vemurafenib.
abstract: Metastatic melanoma is traditionally diagnosed using classic morphologic features in addition to immunohistochemical studies. The authors report a case of metastatic malignant melanoma where both morphology and immunohistochemistry were altered after treatment. This 51-year-old patient presented with metastatic melanoma to the brain and axilla. Initially, both metastases showed classic morphology and diffuse staining with the pan-melanoma antibody cocktail. This cocktail is a combination of 3 antibodies commonly used to diagnose melanocytic neoplasms: Melan-A (MART-1), tyrosinase, and HMB-45. In combination, the cocktail is highly sensitive for detecting melanocytic neoplasms and is commonly used to diagnose metastatic melanoma. Her tumor was positive for the BRAF 1799T>A (V600E) mutation, and she was treated with BRAF inhibitor therapy (vemurafenib). However, the axillary tumor recurred after treatment with vemurafenib. The recurrent tumor showed a markedly different morphology and complete loss of staining with the pan-melanoma antibody cocktail. This loss of staining accompanied by the change in morphology was an observation not previously documented after therapy with vemurafenib. This case demonstrates a potential pitfall in the diagnosis of metastatic or recurrent malignant melanoma.
authors.affiliation: Department of Pathology, Medical College of Georgia, Georgia Regents University, Augusta, GA.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Powell
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Sheehan
authors.forename: Daniel T
authors.initials: DT
authors.lastname: Kleven
mesh_terms: D000970:Antineoplastic Agents / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000032:analysis; D001932:Brain Neoplasms / Q000188:drug therapy / Q000556:secondary; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007211:Indoles / Q000627:therapeutic use*; D008207:Lymphatic Metastasis / Q000473:pathology; D008545:Melanoma / Q000188:drug therapy* / Q000556:secondary*; D008875:Middle Aged; D012878:Skin Neoplasms; D013449:Sulfonamides / Q000627:therapeutic use*; D000077484:Vemurafenib; D000096142:Cutaneous Malignant Melanoma
chemical_list: D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D007211:Indoles; D013449:Sulfonamides; D000077484:Vemurafenib