Definition of R1 resection in thyroid carcinoma

The residual tumor (R) classification describes the tumor status after therapy, which in patients with thyroid carcinomas is predominantly after surgical treatment. The aim of the R classification is to indicate the success of (surgical) therapy, which can influence further therapeutic procedures and allow relevant prognostic statements. Definition of R1 resection as well as minimally invasive extrathyroidal growth of thyroid carcinomas as the latter is a common prerequisite for R1 resected thyroid carcinoma. Presentation of the pathological work-up and histopathological assessment. Proposal to supplement and extend the recently introduced 8th edition of the TNM classification in order to systematically classify minimally invasive extrathyroidal carcinomas. The presented definitions (e.g. R1, minimally invasive extrathyroidal invasion) in combination with the proposed extension of the TNM classification permit the prospective scientific assessment of the biological relevance of these two parameters.