Improving diagnostic accuracy in atypical melanocytic tumors using p16 immunohistochemistry and 9p21 fluorescence in situ hybridization: analysis of 206 second opinion cases

Abstract Diagnosing atypical melanocytic tumors can be challenging without molecular characterization, necessitating simple tools to enhance diagnostic accuracy in daily practice. This study retrospectively analyzed the utility of p16 immunohistochemistry (IHC) and 9p21 fluorescence in situ hybridiz...

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Main Authors: Rémi Vergara, Elodie Laharanne, Arnaud de la Fouchardière, Audrey Gros, Jean-Philippe Merlio, Mathilde Guyon, Caroline Dutriaux, Marie Beylot-Barry, Béatrice Vergier, Fanny Beltzung
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Language:English
Published: Nature Portfolio 2025-04-01
Series:Scientific Reports
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Online Access:https://doi.org/10.1038/s41598-025-95785-2
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author Rémi Vergara
Elodie Laharanne
Arnaud de la Fouchardière
Audrey Gros
Jean-Philippe Merlio
Mathilde Guyon
Caroline Dutriaux
Marie Beylot-Barry
Béatrice Vergier
Fanny Beltzung
author_facet Rémi Vergara
Elodie Laharanne
Arnaud de la Fouchardière
Audrey Gros
Jean-Philippe Merlio
Mathilde Guyon
Caroline Dutriaux
Marie Beylot-Barry
Béatrice Vergier
Fanny Beltzung
author_sort Rémi Vergara
collection DOAJ
description Abstract Diagnosing atypical melanocytic tumors can be challenging without molecular characterization, necessitating simple tools to enhance diagnostic accuracy in daily practice. This study retrospectively analyzed the utility of p16 immunohistochemistry (IHC) and 9p21 fluorescence in situ hybridization (FISH) on 206 tumors referred for expert second opinion. The performance of p16 and 9p21 was compared to histological diagnosis (both initial and final respectively without and with p16 and 9p21 status), histological subtype, and follow-up data. Negative p16 immunolabelling detected 90% of malignant cases, while only 11% of benign tumors were p16 negative. Homozygous 9p21deletion detected 42% of malignant tumors and excluded 95% of benign ones. Heterozygous deletion showed no diagnostic value. Homozygous 9p21 deletion significantly improved diagnostic confidence (P < 0.001), leading to tumor upgrading (n = 23) or melanoma confirmation (n = 22). Among 97 patients with follow-up, 17 had adverse outcomes. Kaplan–Meier analysis showed no significant difference in progression-free survival between groups (P = 0.64). Combining both techniques ultimately enhanced histological diagnostic confidence in daily practice. However, in cases where p16 is negative without homozygous deletion, or where histological malignancy is uncertain and p16 positive, other p16-inactivation mechanisms or molecular anomalies should be considered, necessitating further molecular investigations.
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spelling doaj-art-e8ef8fb0d7614b4e9f224c43f77d745b2025-08-20T01:54:30ZengNature PortfolioScientific Reports2045-23222025-04-0115111410.1038/s41598-025-95785-2Improving diagnostic accuracy in atypical melanocytic tumors using p16 immunohistochemistry and 9p21 fluorescence in situ hybridization: analysis of 206 second opinion casesRémi Vergara0Elodie Laharanne1Arnaud de la Fouchardière2Audrey Gros3Jean-Philippe Merlio4Mathilde Guyon5Caroline Dutriaux6Marie Beylot-Barry7Béatrice Vergier8Fanny Beltzung9Department of Pathology, Bordeaux University HospitalDepartment of Molecular Pathology, Bordeaux University HospitalDepartment of Pathology, Léon Bérard CenterDepartment of Molecular Pathology, Bordeaux University HospitalDepartment of Molecular Pathology, Bordeaux University HospitalDepartment of Dermatology, Bordeaux University HospitalBoRdeaux Institute of onCology (BRIC), UMR 1312 INSERM University of BordeauxBoRdeaux Institute of onCology (BRIC), UMR 1312 INSERM University of BordeauxDepartment of Pathology, Bordeaux University HospitalDepartment of Pathology, Bordeaux University HospitalAbstract Diagnosing atypical melanocytic tumors can be challenging without molecular characterization, necessitating simple tools to enhance diagnostic accuracy in daily practice. This study retrospectively analyzed the utility of p16 immunohistochemistry (IHC) and 9p21 fluorescence in situ hybridization (FISH) on 206 tumors referred for expert second opinion. The performance of p16 and 9p21 was compared to histological diagnosis (both initial and final respectively without and with p16 and 9p21 status), histological subtype, and follow-up data. Negative p16 immunolabelling detected 90% of malignant cases, while only 11% of benign tumors were p16 negative. Homozygous 9p21deletion detected 42% of malignant tumors and excluded 95% of benign ones. Heterozygous deletion showed no diagnostic value. Homozygous 9p21 deletion significantly improved diagnostic confidence (P < 0.001), leading to tumor upgrading (n = 23) or melanoma confirmation (n = 22). Among 97 patients with follow-up, 17 had adverse outcomes. Kaplan–Meier analysis showed no significant difference in progression-free survival between groups (P = 0.64). Combining both techniques ultimately enhanced histological diagnostic confidence in daily practice. However, in cases where p16 is negative without homozygous deletion, or where histological malignancy is uncertain and p16 positive, other p16-inactivation mechanisms or molecular anomalies should be considered, necessitating further molecular investigations.https://doi.org/10.1038/s41598-025-95785-2p16FISHAmbiguous melanocytic tumourMelanomaNaevusSecond opinion
spellingShingle Rémi Vergara
Elodie Laharanne
Arnaud de la Fouchardière
Audrey Gros
Jean-Philippe Merlio
Mathilde Guyon
Caroline Dutriaux
Marie Beylot-Barry
Béatrice Vergier
Fanny Beltzung
Improving diagnostic accuracy in atypical melanocytic tumors using p16 immunohistochemistry and 9p21 fluorescence in situ hybridization: analysis of 206 second opinion cases
Scientific Reports
p16
FISH
Ambiguous melanocytic tumour
Melanoma
Naevus
Second opinion
title Improving diagnostic accuracy in atypical melanocytic tumors using p16 immunohistochemistry and 9p21 fluorescence in situ hybridization: analysis of 206 second opinion cases
title_full Improving diagnostic accuracy in atypical melanocytic tumors using p16 immunohistochemistry and 9p21 fluorescence in situ hybridization: analysis of 206 second opinion cases
title_fullStr Improving diagnostic accuracy in atypical melanocytic tumors using p16 immunohistochemistry and 9p21 fluorescence in situ hybridization: analysis of 206 second opinion cases
title_full_unstemmed Improving diagnostic accuracy in atypical melanocytic tumors using p16 immunohistochemistry and 9p21 fluorescence in situ hybridization: analysis of 206 second opinion cases
title_short Improving diagnostic accuracy in atypical melanocytic tumors using p16 immunohistochemistry and 9p21 fluorescence in situ hybridization: analysis of 206 second opinion cases
title_sort improving diagnostic accuracy in atypical melanocytic tumors using p16 immunohistochemistry and 9p21 fluorescence in situ hybridization analysis of 206 second opinion cases
topic p16
FISH
Ambiguous melanocytic tumour
Melanoma
Naevus
Second opinion
url https://doi.org/10.1038/s41598-025-95785-2
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