RYTHMIC (Réseau tumeurs THYMiques et Cancer) is a nationwide network for TET appointed in 2012 by the French National Cancer Institute. The objectives of the network are management of clinical tumor board and central pathologic review of all cases. RYTHMIC Tumor Board is based on initial histopathological diagnosis.
Pathological central review of patients diagnosed with TET from January 2012 to May 2016 was made by a panel of 10 expert pathologists from the working group. Assessment of agreement or disagreement between the initial institution and the panel review was made according the WHO 2004/2015 and new ITMIG proposals for histologic typing and staging. Discordances were classified as “major” when they would have changed the therapy or management of patients according to the RYTHMIC guidelines.
A total of 400 specimens were reviewed. Considering either histological subtype and/or staging, a total of 172 discordances in 157 patients (39%) were identified as follow: 111 concerning histological diagnosis and 61 regarding stage. A total of 31 major discordances in 29 patients (7%) were identified: 18 patients for whom post-surgical treatment recommendation concerning adjuvant radiotherapy would have been changed and 11 patients for whom management of disease should have been modified. The most frequent disagreement was the sub-diagnosis of stage III reflecting the underlying difficulty in pericardial and/or mediastinal pleura histological invasion. Additionally, major disagreement between the initial and panel pathology's stage and subsequent interpretation by the working group at national tumor board was found in 4 patients, enhancing the importance of an expert pathologist at the RYTHMIC network committee.
The RYTHMIC experience confirms the relevance of an expert histopathological panel diagnosis of thymic malignancies and for better decision-making in particular concerning post-operative radiotherapy to avoid over- or under-treatment of the patients.
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All authors have declared no conflicts of interest.