Florence Granel-Brocard, Alain Dupuy, D. Legoupil, Jean-Jacques Grob, Marie Beylot-Barry, Marie-Thérèse Leccia, Jean-Philippe Arnault, Florence Brunet-Possenti, A. Bardet, Pierre-Emmanuel Stoebner, Céleste Lebbe, Stéphane Dalle, Eve Maubec, Clara Allayous, Isabelle Borget, Bernard Guillot, Brigitte Dréno, Julie DeQuatrebarbes, Philippe Saiag, Laurent Mortier, Marguerite Kandel, Sophie Dalac, Caroline Dutriaux, Thierry Lesimple, Stefan Michiels, Henri Montaudié, François Aubin, Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut Gustave Roussy (IGR), Centre de Recherche en Cancérologie de Lyon (UNICANCER/CRCL), Centre Léon Bérard [Lyon]-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Service de biostatistique et d'épidémiologie (SBE), Direction de la recherche clinique [Gustave Roussy], Institut Gustave Roussy (IGR)-Institut Gustave Roussy (IGR), Immunologie humaine, physiopathologie & immunothérapie (HIPI (UMR_S_976 / U976)), Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Paris Cité (UPCité), Thérapies Laser Assistées par l'Image pour l'Oncologie - U 1189 (ONCO-THAI), Institut National de la Santé et de la Recherche Médicale (INSERM)-Université de Lille-Centre Hospitalier Régional Universitaire [Lille] (CHRU Lille), Groupe hospitalier Saint-André, Centre Hospitalier Régional Universitaire [Montpellier] (CHRU Montpellier), Centre Hospitalier Universitaire [Grenoble] (CHU), Centre Hospitalier Universitaire de Dijon - Hôpital François Mitterrand (CHU Dijon), Centre Hospitalier Régional Universitaire de Brest (CHRU Brest), Hôpital Ambroise Paré [AP-HP], Centre Hospitalier Universitaire de Nice (CHU Nice), Service de dermatologie [CHU d'Amiens-Picardie], CHU Amiens-Picardie, AP-HP - Hôpital Bichat - Claude Bernard [Paris], Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP), Service de dermatologie, vénéreologie et cancérologie cutanée [Hôpital de la Timone - APHM], Aix Marseille Université (AMU)-Assistance Publique - Hôpitaux de Marseille (APHM)- Hôpital de la Timone [CHU - APHM] (TIMONE), Centre Hospitalier Annecy-Genevois [Saint-Julien-en-Genevois], Service de dermatologie [Bordeaux], Université Bordeaux Segalen - Bordeaux 2-CHU Bordeaux [Bordeaux]-Hôpital Haut-Lévêque [CHU Bordeaux], CHU Bordeaux [Bordeaux], CRLCC Eugène Marquis (CRLCC), Centre Hospitalier Régional Universitaire de Besançon (CHRU Besançon), Avicennes University Hospital, Service de Dermatologie et Allergologie [CHRU Nancy], Centre Hospitalier Régional Universitaire de Nancy (CHRU Nancy), Centre Hospitalier Universitaire de Nîmes (CHU Nîmes), Service de Dermatologie [Rennes] = Dermatology [Rennes], CHU Pontchaillou [Rennes], Service de dermatologie [Nantes], Université de Nantes (UN)-Centre hospitalier universitaire de Nantes (CHU Nantes), Oncostat (U1018 (Équipe 2)), Institut Gustave Roussy (IGR)-Centre de recherche en épidémiologie et santé des populations (CESP), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpital Paul Brousse-Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Paris-Saclay-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP)-Hôpital Paul Brousse-Institut National de la Santé et de la Recherche Médicale (INSERM)-Université Paris-Saclay, Centre Léon Bérard [Lyon], AP-HP. Université Paris Saclay, Amgen Pfizer Merck Novartis Roche Janssen Biotech Meso Scale Diagnostics, MSD Array BioPharma Takeda Pharmaceutical Company Sanofi Pasteur British Microcirculation Society, BMS Institut National Du Cancer, INCa: DOC 16‐009, This work was supported by the French National Cancer Institute (DOC 16‐009)., Stéphane Dalle reports institutional research funding Roche, institutional research funding and nonfinancial support from Bristol‐Myers Squibb (BMS), and an immediate family member who is employed by Sanofi and owns stock or other ownership interest in the company. Aurélie Bardet was employed by Roche and held stock and other ownership interest in the company until March of 2018. Clara Allayous reports nonfinancial support from BMS, Amgen, and Roche outside the submitted work. Laurent Mortier reports personal fees and nonfinancial support from Roche, Novartis, BMS, and Merck Sharp & Dohme (MSD) outside the submitted work. Caroline Dutriaux reports personal fees from Roche, BMS, Novartis, MSD, and Pierre Fabre Laboratories outside the submitted work. Philippe Saiag reports research funding and personal fees from Roche, grants, personal fees, and nonfinancial support from BMS, MSD, Novartis, and Pierre Fabre Laboratories, and personal fees from Array, Sanofi, and Merck, all outside the submitted work. Henri Montaudié reports institutional research funding from LeoPharma, institutional research funding, personal fees, and nonfinancial support from BMS, personal fees from Pierre Fabre Laboratories and MSD, and nonfinancial support from Novartis, all outside the submitted work. Jean‐Phillipe Arnault reports institutional research funding and personal fees from BMS and institutional research funding from Novartis outside the submitted work. Jean‐Jacques Grob reports personal fees and nonfinancial support from BMS, Roche, MSD, Novartis, Merck, Amgen, Pierre Fabre Laboratories, Sanofi, and Pfizer and nonfinancial support from Amgen, all outside the submitted work. Julie De Quatrebarbes reports nonfinancial support from BMS, MSD, and Janssen outside the submitted work. Thierry Lesimple reports research funding and personal fees from Roche and personal fees from BMS, MSD, Novartis, Pierre Fabre Laboratories, and Incyte, all outside the submitted work. François Aubin reports personal fees and nonfinancial support from Novartis, MSD, and Roche outside the submitted work. Eve Maubec reports grants, personal fees, and nonfinancial support from MSD, personal fees from Sanofi and Novartis, personal fees and nonfinancial support from BMS, and nonfinancial support from Pierre Fabre Laboratories, all outside the submitted work. Stefan Michiels reports personal fees from IDDI Belgium, Janssen Cilag France, Hexal, Johnson & Johnson, Ipsen, Genticel, Mabxience, Steba, IQVIA, Roche, Sensorion, Biophytis, and Servier, all outside the submitted work. Céleste Lebbe reports institutional research funding, personal fees, and nonfinancial support from BMS, institutional funding and personal fees from Roche, personal fees and nonfinancial support from MSD, and personal fees from Aventis, Novartis, Amgen, Pierre Fabre Laboratories, Pfizer, and Incyte, all outside the submitted work. Isabelle Borget reports research funding from the BMS Foundation during the course of the study and personal fees from Roche, Janssen, CSC Behring, Novartis, and Takeda outside the submitted work. The remaining authors made no disclosures., Institut National de la Santé et de la Recherche Médicale (INSERM)-Université de Paris (UP), and Hôpital de la Timone [CHU - APHM] (TIMONE)-Assistance Publique - Hôpitaux de Marseille (APHM)-Aix Marseille Université (AMU)