Diagnostics of malignant melanoma of the skin: Recommendations of the current S3 guidelines on histology and molecular pathology

Abstract

The updated S3 guidelines on malignant melanoma were established in August 2016. The principles of diagnostics and classification are based on the histopathological results from the primary tumor and if necessary the sentinel lymph nodes. The most important factor for prognosis is the tumor thickness according to Breslow and the detection of sentinel node micrometastases. The surgical safety margin after excision is dependent on the tumor thickness. Furthermore, ulceration of the primary tumor and presence of mitosis in melanomas less than 1 mm in thickness are also considered in the T‑classification. The sentinel lymph nodes should be prepared according to established procedures using HE staining and immunohistochemical methods. The largest tumor diameter of a micrometastasis should be measured in tenths of a millimeter (Rotterdam classification). Molecular pathology testing for mutations in the BRAF and NRAS oncogenes should be carried out in patients with metastatic disease or surgically non-resectable tumors. In addition c-KIT mutations should be tested in acral lentiginous and mucosal melanomas. Treatment with signal transduction inhibitors is possible when mutations have been detected.