Multimodality imaging and genetics of primary mucosal melanomas and response to treatment

Mucosal melanomas (MMs) are rare and aggressive tumors that arise from melanocytes in the mucosal tissues that line the respira-tory, gastrointestinal, and urogenital tracts. Most MMs occur during the 6th and 7th decades of life. MMs may be asymptomatic but may also cause bleeding, pain, and itching, depending on the site of origin. Because of their asymptomatic or oligosymptomatic nature and the difficulty of visualizing them in some cases, they are often advanced tumors at patient presentation. MM staging varies depending on the site of the primary tumor. A simplified staging system allows classification of clinically localized disease as stage I, regional nodal involvement as stage II, and distant metastasis as stage III. MM differs genetically from its cutaneous counterparts. Common drivers in cutaneous melanoma such as B-raf proto-oncogene serine/threonine kinase (BRAF) have a lower mutation rate in MM, whereas mutations of other genes including the KIT proto-oncogene, receptor tyrosine kinase (KIT) and splicing factor 3b subunit 1 gene (SF3B1) are more common in MM. Complete resection is the best curative option. However, surgical interven-tion with wide local excision and negative margins may be difficult to attain because of the local anatomy and the extent of disease. In addition, despite aggressive surgical resection, most patients de-velop local recurrence and metastatic disease. Recent advances in the treatment of melanoma include immunotherapy and targeted therapy. Unfortunately, MMs have a relatively poor prognosis, with an overall 5-year survival rate of 25%.