[Diagnostic and treatment pitfalls and guidelines for variants of squamous cell carcinomas of the head and neck: on behalf of the REFCOR].

Among the 20,000 new cases of head and neck neoplasms in France each year, squamous cell carcinomas (HNSCC) represent about 90 % of the cases. Among these, variants of conventional squamous cell carcinomas represent between 5% and 10% of cases. Patient history and risk factors are often similar from those of conventional HSNCC. Variants may, however, be misdiagnosed, which can lead to therapeutic mismanagement due to confusion with sarcomas, glandular tumors or even benign tumors. Diagnostic workup needs to be more cautionary or to include additional exams not to omit their most aggressive component in the case of composite tumors or to under stage the tumor. Immunohistochemistry and specific molecular analyses may be required for proper diagnosis. Central pathological review may also be essential for some of these variants. In addition, some variants are radioresistant and, conversely, others are radiosensitive. An update of the REFCOR 2008 standards was carried out in the light of the international literature and the 2017 WHO/IARC classification for the seven main variants of HNSCC, verrucous, acantholytic (to be named adenoid carcinomas), basaloid, papillary, spindle cell (incorrectly named sarcomatoid), adenosquamous and lymphoepithelial carcinomas.