title: Immunohistochemistry is highly sensitive and specific for the detection of NRASQ61R mutation in melanoma.
abstract: Testing for NRAS is now integral part in the assessment of metastatic melanoma patients because there is evidence that NRAS-mutated patients may be sensitive to MEK inhibitors, and RAS mutation is a common mechanism of acquired resistance during treatment with BRAF inhibitors. This study evaluated the sensitivity and specificity of immunohistochemical analysis using an N-Ras (Q61R) antibody to detect the presence of the NRASQ61R mutation in melanoma patients. A total of 98 primary cutaneous melanomas that have undergone examination of NRAS mutation were retrieved from a multicentric database. Formalin-fixed and paraffin-embedded melanoma tissues were analyzed for BRAF and NRAS mutations by independent, blinded observers using both conventional DNA molecular techniques and immunohistochemistry with the novel anti-human N-Ras (Q61R) monoclonal antibody (clone SP174). The antibody showed a sensitivity of 100% (14/14) and a specificity of 100% (83/83) for detecting the presence of an NRASQ61R mutation. Of the NRAS-mutated cases, none of the non-Q61R cases stained positive with the antibody (0/7). There were three cases with discordant NRAS mutational results. Additional molecular analysis confirmed the immunohistochemically obtained NRAS result in all cases, suggesting that a multiple analytical approach can be required to reach the correct sample classification. The reported immunohistochemical method is an accurate, rapid, and cost-effective method for detecting NRASQ61R mutation in melanoma patients, and represents a valuable supplement to traditional mutation testing. If validated in further studies, genetic testing would only be required for immunohistochemistry-negative patients to detect non-Q61R mutations.
authors.affiliation: Division of Pathological Anatomy, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Massi
authors.affiliation: Clinical Biochemistry Unit, Department of Biomedical, Experimental and Clinical Sciences, University of Florence, Florence, Italy.
authors.forename: Lisa
authors.initials: L
authors.lastname: Simi
authors.affiliation: Laboratory of Molecular Pathology, UO Pathological Anatomy III, Pisa, Italy.
authors.forename: Elisa
authors.initials: E
authors.lastname: Sensi
authors.affiliation: Division of Pathological Anatomy, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy.
authors.forename: Gianna
authors.initials: G
authors.lastname: Baroni
authors.affiliation: Unit of Mechanisms of Cancer, Friedrich Miescher Institute for Biomedical Research, Basel, Switzerland.
authors.forename: Gongda
authors.initials: G
authors.lastname: Xue
authors.affiliation: Division of Pathological Anatomy, Department of Surgery and Translational Medicine, University of Florence, Florence, Italy.
authors.forename: Cristian
authors.initials: C
authors.lastname: Scatena
authors.affiliation: Clinical and Descriptive Epidemiology Unit, Institute for Study and Cancer Prevention (ISPO), Florence, Italy.
authors.forename: Adele
authors.initials: A
authors.lastname: Caldarella
authors.affiliation: Clinical Biochemistry Unit, Department of Biomedical, Experimental and Clinical Sciences, University of Florence, Florence, Italy.
authors.forename: Pamela
authors.initials: P
authors.lastname: Pinzani
authors.affiliation: Laboratory of Molecular Pathology, UO Pathological Anatomy III, Pisa, Italy.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Fontanini
authors.affiliation: Research Foundation, Papa Giovanni XXIII Hospital, Bergamo, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: Carobbio
authors.affiliation: Dermatopathology Section, SM Annunziata Hospital, Florence, Italy.
authors.forename: Carmelo
authors.initials: C
authors.lastname: Urso
authors.affiliation: Unit of Medical Oncology, Division of Medical Oncology, Department of Oncology and Haematology, Papa Giovanni XXIII Hospital, Bergamo, Italy.
authors.forename: Mario
authors.initials: M
authors.lastname: Mandalà
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D005260:Female; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008545:Melanoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D008875:Middle Aged; D009154:Mutation; D012680:Sensitivity and Specificity; D012878:Skin Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D055815:Young Adult
chemical_list: D008565:Membrane Proteins; D020558:GTP Phosphohydrolases; C579846:NRAS protein, human