title: Loss of S100 antigenicity in metastatic melanoma.
abstract: Melanoma is a highly malignant disease that may initially present as a poorly differentiated metastatic tumor. Therefore, the S100 immunostain, immunoreactive in 96% to 99% of melanoma, is used to evaluate poorly differentiated malignant tumors. To develop criteria for correctly diagnosing S100-negative melanomas, we studied the immunohistochemical profile of 1553 patients enrolled in ongoing National Cancer Institute clinical trials for melanoma. Seventeen patients (1%) had metastatic melanoma specimens that were negative for S100. Of the 17 S100-negative lesions, 10 (59%) were immunoreactive for both GP100 and MART-1. Of the 17 S100-negative cases, 13 had a documented primary melanoma. Twenty-four percent of the S100-negative cases had an ocular primary, whereas only 6% of all melanomas had an ocular origin. In 11 of the 17 cases with previous surgical specimens, a prior documented S100-immunoreactive specimen was identified in 9 cases (82%). The time interval for loss of S100 immunoreactivity ranged from 3 weeks to 3 years (average, 13.5 months). There was no association between S100-negative status and histological appearance or site of metastasis. We conclude that all S100-negative melanomas could be correctly identified by negative workup for carcinoma, lymphoma, and sarcoma plus (1) GP100/MART-1 immunoreactivity and/or (2) prior documentation of melanoma.
authors.affiliation: Laboratory of Pathology, National Cancer Institute, Bethesda, MD 20892, USA.
authors.forename: Dara L
authors.initials: DL
authors.lastname: Aisner
authors.forename: Ajay
authors.initials: A
authors.lastname: Maker
authors.forename: Steven A
authors.initials: SA
authors.lastname: Rosenberg
authors.forename: David M
authors.initials: DM
authors.lastname: Berman
mesh_terms: D014408:Biomarkers, Tumor; D005134:Eye Neoplasms / Q000378:metabolism / Q000473:pathology; D006801:Humans; D016130:Immunophenotyping; D008545:Melanoma / Q000378:metabolism* / Q000473:pathology; D009362:Neoplasm Metastasis; D009418:S100 Proteins / Q000276:immunology / Q000378:metabolism*; D012878:Skin Neoplasms / Q000378:metabolism / Q000473:pathology
chemical_list: D014408:Biomarkers, Tumor; D009418:S100 Proteins