Cutaneous lymphatic drainage in patients with grossly involved nodal basins

Background: The development of lymphatic mapping techniques has facilitated the identification of the sentinel lymph node (SLN), the first node in the regional basin into which cutaneous lymphatics flow from a particular skin area. Previous studies have shown that SLN histology reflects the histolog y of the entire basin, because melanoma metastases progress in an orderly f ashion, involving the SLN before higher nodes in the basin become involved with metastatic disease, it is uncertain whether these orderly cutaneous ly mphatic flow patterns are maintained in grossly involved basins. Lymphatic mapping was performed in a population of melanoma patients with clinically palpable lymphadenopathy to address this question. We aimed to determine wh ether the presence of gross nodal disease in the basin alters lymphatic flo w into that basin so that lymphatic mapping techniques are not applicable, and, in patients referred with a grossly involved basin, whether preoperati ve lymphoscintigraphy should be performed to identify other regional basins at risk for metastases. Methods: Eight patients presented with grossly palpable disease in the regi onal basin acid underwent preoperative lymphoscintigraphy. All patients wit h palpable disease and all basins indicated by lymphoscintigraphy to be at risk were dissected. Three patients presented with clinically palpable node s at the time of diagnosis, and five developed nodal disease on clinical fo llow-up after undergoing initial wide local excision only. A total of 10 ba sins in the eight patients were dissected. Of these, eight of the basins ha d grossly palpable regional nodal disease, and the other two basins were id entified by preoperative lymphoscintigraphy as being at risk for metastases . The SLN was identified with intraoperative mapping, harvested, and submit ted to pathology. Complete therapeutic lymph node dissections were performe d following the SLN harvest in the basins with grossly palpable disease. SL N biopsy alone was performed in the two basins that did not have clinically palpable adenopathy but showed cutaneous lymphatic flow from the scintigra m. Results: Sixteen SLNs were harvested from these eight basins with grossly p alpable disease, and 14 (87.5%) contained tumor. In each case, one of the S LNs was the grossly palpable node, and in six of the basins (75%) it was th e only site of melanoma metastases. An additional 190 higher level, non-SLN s were removed, 32 (16.8%) of which contained microscopic foci of metastati c melanoma (P = .015). The null hypothesis that melanoma nodal metastasis i s a random event is rejected. Two patients with trunk; melanoma primary sit es were identified to have other basins at risk for metastatic disease on l ymphoscintigraphy. SLN biopsies were performed in these two patients, and o ne had microscopic nodal disease in the SLN. Conclusions: These data support the fact that cutaneous lymphatic drainage patterns are maintained in patients with grossly involved basins, thus butt ressing the idea that the SLN is the nude most likely to develop metastatic disease. Gross disease in the basin does not significantly alter cutaneous lymphatic flow into the regional basin, as the sentinel lymph node identif ied under these circumstances is the same as with the grossly involved node . Preoperative lymphoscintigraphy in patients who present with grossly invo lved nodes in one basin may identify other regional basins with micrometast atic disease and deserves further study in this setting.