Lymphatic drainage to the popliteal basin in distal lower extremity malignant melanoma

Hypotheses Melanoma of the distal lower extremity may drain to the popliteal basin. Drainage pathways and retrieval of the popliteal sentinel nodes may affect patient outcome. DESIGN: Retrospective analysis of popliteal involvement in patients with stage IB or higher melanoma, operated on from August 1, 1993, to July 31, 2003. SETTING: Tertiary referral, university-affiliated medical center. PATIENTS: One hundred six melanoma patients who underwent combined lymphoscintigraphy and blue dye-guided sentinel node biopsy, radical popliteal dissection, or both. MAIN OUTCOME MEASURES: Incidence and patterns of drainage to popliteal nodes; effect on staging and outcome. RESULTS: Lymphoscintigraphy (n = 8) and physical examination (n = 2) identified 10 cases (9%) of draining to the popliteal basin, with concurrent drainage to the groin. Three distinct drainage patterns were identified, with different popliteal node locations. Seven of 8 popliteal sentinel nodes were retrieved, 1 of which was metastatic with no groin metastasis. Two patients had synchronous palpable popliteal and groin metastases and underwent radical groin and popliteal dissection. All 3 patients with popliteal metastases relapsed early with synchronous systemic and in-transit disease. One of 7 patients with negative sentinel nodes is alive with in-transit disease; all others are disease free. CONCLUSIONS: According to this series, the popliteal basin is the site of first drainage in about 9% of patients, with concurrent drainage to the groin. The 3 distinct patterns of drainage to the popliteal region and the presence of isolated popliteal metastases may affect the surgical treatment. Therefore, drainage to popliteal sentinel nodes and the pattern of this drainage should be noted in all distal lower extremity melanomas.