Lymphoscintigraphy for sentinel lymph node mapping in Japanese patients with malignant skin neoplasms of the lower extremities: comparison with previously investigated Japanese lymphatic anatomy Hiroyuki MiuraShuichi OnoMorio NagahataKoichi ShibutaniShinya KakehataKohei Morimoto • Hiroko SeinoAkihisa KakutaMasahiko AokiYoshiomi HatayamaHideo Kawaguchi • Yoshihiro TakaiYoshinao AbeTakahide KanekoDaisuke SawamuraKatsumi Hanada

Objectives Lymph nodes (LN) and lymphatic drainage were identified by lymphoscintigraphy using 99m Tc-phytate in order to map the sentinel lymph nodes (SLNs) in patients with malignant skin neoplasms of the lower extremities, and to compare the results with an atlas of Japanese lymphatic anatomy. Methods Sentinel lymphoscintigraphs of 18 patients with malignant skin neoplasms of the lower extremities (9 men, 9 women; age range 45‐84 years, mean age 66 years) were analyzed retrospectively, and the LNs detected were identified as SLNs or secondary nodes. Results The patterns of lymphatic drainage were divided into three different categories: (1) initial drainage into inguinal LN without visualization of popliteal LNs (inguinal type), (2) initial drainage into popliteal LNs and then into intrapelvic LNs (popliteal type), and (3) initial drainage into both popliteal and inguinal LNs (inguinal and popliteal type). More than half of the cases were the inguinal and popliteal type, as both inguinal and popliteal LNs were identified as SLNs. In the cases in which the hallux and its surrounding area were injected, all were the inguinal type and popliteal LNs were not visualized. In one case, only dynamic images detected lymphatic drainage without visualization of popliteal LNs. In contrast to the previously published literature on Japanese lymphatic anatomy, SLN lymphatic drainage from the skin of the lower extremities was wide and overlapping in many areas. However, in agreement with currently accepted anatomy, only the great saphenous lymphatic vessel drained the skin of the hallux and its surrounding area. The present results suggest that it is important to confirm lymphatic drainage in order to identify SLNs in the lower extremities. Conclusions The patterns of lymphatic drainage from the skin of the foot were divided into three different categories. In contrast to previously published Japanese lymphatic anatomy, lymphatic drainage from the skin of the lower extremities was wide and overlapping in many areas. However, only the great saphenous lymphatic vessel drained the skin of the hallux and its surrounding area in agreement with currently accepted Japanese lymphatic anatomy. It is important to confirm lymphatic drainage to identify SLNs in the lower extremities.