// Jilliana Monnier 1,* , Sophie Georgin-Lavialle 1,2,* , Danielle Canioni 2,3 , Ludovic Lhermitte 2,3 , Michael Soussan 4 , Michel Arock 5,6 , Julie Bruneau 2,3 , Patrice Dubreuil 2,7 , Christine Bodemer 2,8 , Marie-Olivia Chandesris 2 , Olivier Lortholary 2 , Olivier Hermine 2,9 and Gandhi Damaj 2,10,11 1 Service de Medecine Interne, Hopital Tenon, Universite Paris VI, Assistance Publique-Hopitaux de Paris (AP-HP), Paris, France 2 Centre de Reference des Mastocytoses, Faculte de Medecine et AP-HP Necker-Enfants Malades, Paris, France 3 Laboratoire d’Anatomie-Pathologie, Universite Paris Descartes, Paris Sorbonne Cite, Faculte de Medecine et AP-HP Necker-Enfants Malades, Paris, France 4 Departement de Medecine Nucleaire, Hopital Avicenne, AP-HP et Universite Paris 13, Bobigny, France 5 Laboratoire d’Hematologie, Groupe Hospitalier Pitie-Salpetriere, AP-HP, Paris, France 6 LBPA CNRS UMR8113, Ecole Normale Superieure de Cachan, Cachan, France 7 Inserm, U1068, CRCM, [Signaling, Hematopoiesis and Mechanism of Oncogenesis], Institut Paoli-Calmettes, Marseille, Aix-Marseille Univ, CNRS UMR7258, Marseille, France 8 Service de Dermatologie de l’Hopital Necker Enfants-Malades, AP-HP, Paris, France 9 Service d’hematologie Adulte, Universite Paris Descartes et Institut Imagine, Hopital Necker-Enfants Malades, Paris, France 10 Institut d’Hematologie de Basse Normandie, Centre Hospitalier Universitaire, Caen, France 11 Microenvironnement Cellulaire et Pathologies, Normandie Univ, Unicaen, MILPAT, Caen, France * These authors have contributed equally to this work Correspondence to: Gandhi Damaj, email: // Keywords : mast cell, mastocytosis, mast cell sarcoma, KIT mutations, targeted therapies Received : March 06, 2016 Accepted : August 24, 2016 Published : Spetember 01, 2016 Abstract Mast cell sarcoma (MCS) is a rare form of mastocytosis characterized by the presence of solid tumor(s) comprising malignant mast cells that harbor destructive infiltration capability and metastatic potential. Here, we present an extensive literature review and report on 23 cases of MCS, including 3 new cases from the French National Reference Center for Mastocytosis. From our analysis, it appears that MCS can occur at any age. It can manifest de novo or, to a lesser extent, may evolve from a previously established mastocytosis. Bone tumor is a frequent manifestation, and symptoms of mast cell activation are rare. Histological diagnosis can be difficult because MCS is frequently composed of highly atypical neoplastic mast cells and can thus mimic other tumors. Unexpectedly, the canonical KIT D816V mutation is found in only 21% of MCS; therefore, complete KIT gene sequencing is required. The prognosis of patients with MCS is poor, with a median survival time of less than 18 months, and progression to mast cell leukemia is not unusual. Because conventional chemotherapies usually fail, the role of targeted therapies and bone marrow transplantation warrants further investigation in such aggressive neoplasms.