title: BRAFV600E immunopositive melanomas show low frequency of heterogeneity and association with epithelioid tumor cells: a STROBE-compliant article.
abstract: Treatment of BRAFV600E-mutant melanoma by small molecule inhibitors that target BRAFV600E or MEK kinases is increasingly used in clinical practice and significantly improve patient outcome. However, patients eventually become resistant and therapeutic improvement is required. Molecular diversity within individual tumors (intratumor heterogeneity) and between tumors within a single patient (intrapatient heterogeneity) poses a significant challenge to precision medicine. Using immunohistochemistry, we determined the extent of BRAFV600E intratumor and intrapatient heterogeneity and the influence of morphological heterogeneity in a large series of 171 melanomas of 81 patients. The BRAFV600E mutation rate found in our melanoma series is 44%, with none of 22 (0%) melanoma in situ, 23 of 56 (41%) primary tumors, 28 of 59 (48%) regional metastases, and 24 of 34 (71%) distant metastases harboring the mutation. In general, a diffuse homogeneous immunostaining was seen, even in tumors consisting of more than one cell type, that is, epithelioid, spindle, and/or small cell types. Nevertheless, BRAFV600E-mutant melanomas more often had a purely epithelioid cell population (P=0.063), that is more evident among distant metastases (P=0.014). Only two of 75 (3%) mutated specimens (one primary and one metastasis) displayed heterogeneous BRAFV600E expression. The primary tumor was also morphologically heterogeneous and exclusively displayed BRAFV600E in the epithelioid component, confirming an association between BRAFV600E and epithelioid cells. Twenty-eight of 30 patients (93%) had concordant BRAFV600E mutation status between their tumors. Taken together, BRAFV600E intratumor and intrapatient heterogeneity in melanoma is diminutive, nevertheless, the identified exceptions will have important implications for the clinical management of this disease.
authors.affiliation: From the Department of Pathology, Maastricht University Medical Centre, Maastricht, The Netherlands (IV, KvdH, CMHAS, GMJMR, AzH, E-JMS, VJLW); GROW-School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands (KvdH, AzH, E-JMS, VJLW); Department of Clinical Pathology, Atrium Medical Centre Parkstad, Heerlen, The Netherlands (RC); Department of Pathology, St. Laurentius ziekenhuis, Roermond, The Netherlands (APW); and Laboratory of Translational Cell & Tissue Research and Department of Pathology, University Hospital, KULeuven, Leuven, Belgium (JJvdO).
authors.forename: Ivana
authors.initials: I
authors.lastname: Verlinden
authors.forename: Karin
authors.initials: K
authors.lastname: van den Hurk
authors.forename: Ruud
authors.initials: R
authors.lastname: Clarijs
authors.forename: Arjan P
authors.initials: AP
authors.lastname: Willig
authors.forename: Cecile M H A
authors.initials: CMHA
authors.lastname: Stallinga
authors.forename: Guido M J M
authors.initials: GMJM
authors.lastname: Roemen
authors.forename: Joost J
authors.initials: JJ
authors.lastname: van den Oord
authors.forename: Axel
authors.initials: A
authors.lastname: Zur Hausen
authors.forename: Ernst-Jan M
authors.initials: EM
authors.lastname: Speel
authors.forename: Véronique J L
authors.initials: VJL
authors.lastname: Winnepenninckx
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004252:DNA Mutational Analysis; D004273:DNA, Neoplasm / Q000235:genetics*; D015622:Epithelioid Cells / Q000276:immunology / Q000378:metabolism* / Q000473:pathology; D005260:Female; D018740:Genetic Heterogeneity; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008545:Melanoma / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008875:Middle Aged; D009154:Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics* / Q000276:immunology / Q000378:metabolism; D012189:Retrospective Studies; D012878:Skin Neoplasms; D055815:Young Adult; D000096142:Cutaneous Malignant Melanoma
chemical_list: D004273:DNA, Neoplasm; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf