Current approaches in managing in-transit metastasis of malignant melanoma: a comprehensive review and proposal of an algorithm

The most common local and regional metastases of melanoma are skin, soft tissue, and lymph nodes. These metastases spread between the primary tumor and the regional lymph node line. The entity referred to in-transit metastasis is used to describe the lesions occurring in the superficial lymphatics at a distance of at least 2 cm from the primary tumor and in the locoregional lymph node line. In-transit metastases constitute 3.4–6.2% of malignant melanomas. This entity differs histopathologically from distant skin metastases spreading hematogenously. This feature leads to differences in the clinical course. According to the American Joint Committee on Cancer criteria, in-transit metastases are classified as stage 3b (no metastatic node involvement) and stage 3c (metastatic node involvement) disease. In this entity, 5-year survival rates have been reported as 54% in stage 3b and 24% in stage 3c. In-transit metastasis is a heterogeneous disease, and this feature leads to some differences in treatment. In order to increase the success rates in the management of this disease, a multidisciplinary approach should be applied and treatment options should be used effectively. In the treatment of in-transit metastases, a single treatment option cannot provide a complete cure and combined therapies should be applied simultaneously. Treatment options include surgical resection, radiotherapy, intralesional treatments, isolated limb perfusion and infusion, electrochemotherapy, targeted therapies, and immunotherapy. Detailed studies on combinations of these treatment options are ongoing. In this article, current approaches in the management of in-transit metastases have been evaluated. Level of evidence: Not gradable