In-transit metastases from malignant melanoma

A 44-year-old man presented with a 3-day history of respiratory distress and blackish pigmentation of the left forearm skin. He had a history of painful blackish non-healing ulcer of the left thumb and underwent amputation of the same 2 months ago. Histopathology had shown a malignant melanoma. Physical examination revealed cachexia with the skin lesions [Figure - 1] mentioned above, with firm, non-tender and enlarged ipsilateral axillary lymph nodes. Further work-up showed right-sided moderate pleural effusion, and multiple lung and liver metastases on CT scan. His pleural fluid was haemorrhagic and cytology was positive for malignant melanoma cells. A metastatic melanoma with typical in-transit metastases of melanoma was diagnosed. After initial stabilization, he was discharged on oral palliative chemotherapy with temozolamide. The patient died of progressive disease after 2 months of therapy.

Figure 1: Multiple blackish nodular lesions (white arrow, panel B) spreading over the flexor aspect of the right forearm away from the primary lesion in the left thumb (not shown in picture) depicting in-transit metastases

In-transit metastasis is defined as any cutaneous metastatic lesion more than 2 cm away from the primary lesion, and in between the primary and regional lymph nodes suggesting spread through lymphatic vessels. This is unique in melanoma depicting subcutaneous lymphogenous spread and over one-third patients present with only in-transit metastases before distant spread. In the absence of distant metastasis, resection of one or more in-transit metastasis can be attempted if complete resection is feasible with acceptable morbidity. In the presence of widespread distant metastases, a multidisciplinary team approach with systemic therapy, loco-regional surgical therapy and radiotherapy can be attempted. Five-year survival of in-transit metastases with/without regional lymph nodal involvement ranges from 36% to 60% as compared to a very dismal outcome in patients with distant cutaneous metastasis or with widespread systemic disease, as was in our case.