title: NRASQ61R Mutation-specific Immunohistochemistry Also Identifies the HRASQ61R Mutation in Medullary Thyroid Cancer and May Have a Role in Triaging Genetic Testing for MEN2.
abstract: A quarter of patients with medullary thyroid carcinoma (MTC) have germline mutations in the RET proto-oncogene indicating MEN2. Therefore genetic testing is recommended for all patients presenting with MTC. Approximately 40% of MTCs have somatic RET mutations. Somatic mutations in the RAS genes are the next most common driver mutations and appear to be mutually exclusive with germline RET mutation. The single most common somatic RAS mutation is HRASQ61R (c.182A>G), reported in 4.6% to 11% of all MTCs. Mutation-specific immunohistochemistry (IHC) initially developed to identify the NRASQ61R mutation in melanoma (clone SP174) has proven highly sensitive and specific. Because the amino acid sequences for the HRAS and NRAS proteins at codon 61 are identical, we postulated that SP174 IHC would also identify the somatic HRASQ61R mutation. IHC with SP174 was performed on a tissue microarray of 68 patients with MTC including 13 (22.8%) with molecularly confirmed MEN2. Seven (10.3%) MTCs demonstrated positive staining. Six of these patients had already undergone germline RET mutation testing as part of clinical care and were all confirmed to be wild type, excluding the diagnosis of MEN2. All SP174 immunohistochemically positive MTCs were proven to have HRASQ61R mutation (and lack KRASQ61R and NRASQ61R) by Sanger sequencing. All MEN2 patients showed negative staining. We conclude that IHC with SP174 is highly specific for the HRASQ61R mutation in MTC. Because current data suggest that this mutation is mutually exclusive with germline RET mutation, IHC may also have a role in triaging formal genetic testing for MEN2.
authors.affiliation: Departments of *Anatomical Pathology ††Endocrinology ∥Endocrine Surgical Unit **Familial Cancer Clinic, Royal North Shore Hospital †Cancer Diagnosis and Pathology Research Group, Kolling Institute of Medical Research §Hormones and Cancer Group, Cancer Genetics Laboratory, Kolling Institute of Medical Research, Royal North Shore Hospital, St Leonards ‡Sydney Medical School, University of Sydney, NSW, Australia ¶Auckland UniServices Sequenom Facility, Liggins Institute #IGENZ Ltd, Auckland, New Zealand.
authors.forename: Jessica
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authors.lastname: Reagh
authors.forename: Martyn
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authors.lastname: Bullock
authors.forename: Juliana
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authors.lastname: Andrici
authors.forename: John
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authors.lastname: Turchini
authors.forename: Loretta
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authors.lastname: Sioson
authors.forename: Adele
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authors.lastname: Clarkson
authors.forename: Nicole
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authors.lastname: Watson
authors.forename: Amy
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authors.lastname: Sheen
authors.forename: Grace
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authors.lastname: Lim
authors.forename: Leigh
authors.initials: L
authors.lastname: Delbridge
authors.forename: Stan
authors.initials: S
authors.lastname: Sidhu
authors.forename: Mark
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authors.lastname: Sywak
authors.forename: Ahmad
authors.initials: A
authors.lastname: Aniss
authors.forename: Phillip
authors.initials: P
authors.lastname: Shepherd
authors.forename: Daniel
authors.initials: D
authors.lastname: Ng
authors.forename: Paul
authors.initials: P
authors.lastname: Oei
authors.forename: Michael
authors.initials: M
authors.lastname: Field
authors.forename: Diana
authors.initials: D
authors.lastname: Learoyd
authors.forename: Bruce G
authors.initials: BG
authors.lastname: Robinson
authors.forename: Roderick J
authors.initials: RJ
authors.lastname: Clifton-Bligh
authors.forename: Anthony J
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authors.lastname: Gill
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000911:Antibodies, Monoclonal; D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics*; D018278:Carcinoma, Neuroendocrine / Q000175:diagnosis / Q000235:genetics*; D004252:DNA Mutational Analysis / Q000379:methods*; D005260:Female; D020558:GTP Phosphohydrolases / Q000235:genetics; D005820:Genetic Testing; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008297:Male; D008565:Membrane Proteins / Q000235:genetics; D008875:Middle Aged; D009377:Multiple Endocrine Neoplasia / Q000175:diagnosis* / Q000235:genetics; D016133:Polymerase Chain Reaction; D000090063:Proto-Oncogene Mas; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D013964:Thyroid Neoplasms / Q000175:diagnosis / Q000235:genetics*; D046888:Tissue Array Analysis; D055815:Young Adult
chemical_list: D000911:Antibodies, Monoclonal; D014408:Biomarkers, Tumor; C000715470:MAS1 protein, human; D008565:Membrane Proteins; D000090063:Proto-Oncogene Mas; D020558:GTP Phosphohydrolases; C579846:NRAS protein, human; C501009:HRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)