A case report of metastatic melanoma in the popliteal fossa

INTRODUCTION: Metastatic melanoma in the popliteal fossa is extremely rare with less than 5% of metastatic deposits from melanomas in the leg and foot draining into the popliteal region, while the majority drain to the inguinal region. If popliteal spread is clinically overlooked, it may lead to recurrence. Together with the accompanying literature review, this case report emphasises the need for thorough clinical and radiological assessment in the management of malignant melanomas of the lower extremity. PRESENTATION OF CASE: A 66-year-old gentleman presented with metastatic melanoma to the right popliteal fossa three years after the diagnosis of a primary lesion in the right mid-calf with ipsilateral inguinal lymph node metastasis for which he underwent a right wide local excision and complete groin lymph node dissection. DISCUSSION: Studies show that a lesion anywhere below the knee can metastasize to the popliteal fossa. The groin can be the primary or secondary lymphatic drainage site in conjunction with the popliteal fossa. Concurrent popliteal and inguinal drainage may either reflect two separate lymphatic channels with popliteal nodes being the primary drainage site, or a single channel which drains to the popliteal basin as an interval node. Hence, popliteal lymph nodes should be carefully assessed in distal lower extremity lesions including melanomas. Modalities to delineate lymphatic flow and identify micrometastatic deposits should be used and when metastatic popliteal disease is identified, radical popliteal dissection is advised. CONCLUSION: Proper clinical assessment, good surgical technique, a high index of suspicion, and active surveillance are all essential to ensure early detection of metastasis to the popliteal region.