Tumeurs épithéliales thymiques

Thymic epithelial tumors (TETs) are rare and potentially agressive intrathoracic malignant cancers difficult to treat. They include thymomas and thymic carcinomas. Reported incidence is estimated between 1.3 and 1.7 per million per year. Annual incidence ranging from <1 (North-Est Europe) and 2 to 3.5/million inhabitants in Central-South continent. Mean age at diagnosis is 40 to 50 years. Approximately 30% of patients also have Myasthenia Gravis. Thymic gland has a lymphocyte and an epithelial component. Only the epithelial component could develop tumour. We can differentiate between encapsulated tumours (stage I in the Masaoka classification, 65% of cases), or invasive tumours (stages II-IV in the Masaoka classification, 35% of cases). Many histological classifications have been proposed. At International Thyme Malignancy Interest Group (ITMIG) consensus meeting in 2011, the World Health Organization (WHO) was validated as the standard for clinical practice. A wide variety of histological subtypes are included in TETs, associated with different clinical outcomes. Thymomas (T) are subdivided into different subtypes (A, AB, B1, B2, B3) based upon the morphology of epithelial tumour cells and lymphocytic component (WHO Classification 2004-2014). Thymic carcinomas (CT) are frequently associated with poor prognosis and the development of distant metastases. IASLC together with ITMIG proposed a consensus TNM based-staging system in 2011 according with Masaoka-Koga classification. Surgery represents the first step of the treatment, as it is the case in Masaoka-Koga stage I/II and some stage III tumours (classified as stage I, II, IIIA/T3 in the IASLC/ITMIG TNM proposed classification). However, approximately one third of these patients will present a recurrence. There is no strong evidence of postoperative treatment. Platinum-based chemotherapy is standard treatment for metastasic, unresectable and/or recurrent disease. Combination regimens with anthracyclines response rate vary from 69% in T to 42% in CT. In addition to multiagent chemotherapy combinations, the efficacy of other types of therapies such as sunitinib and everolimus has been demonstrated. Immunotherapy has shown promising results but its use is limited due to the frequence occurence of auto-immune disease that are a contraindication. Nevertheless, the estimated five years overall survival (OS) for T is 80%, and 40% for patients with CT. TETs mutational profile is poorly detectable by gene panels used for molecular profiling of common solid tumors, KIT mutations being the only potential target identified in up to 10% of the tumors. Additionally, no large study has correlated the a complete molecular profile with tumor subtype or the occruence of an auto-immune disease.