Sentinel lymph node detection by lymphoscintigraphy in malignant melanoma

Sentinel lymph node (SLN) detection is currently employed in patients with malignant melanoma (MM) to spare them unnecessary lymph node dissection.

We investigated 241 patients (130 men and 111 women, median age, 50 years (range, 14-92) with MM (192 before and 51 after surgical biopsy); two of them had more than one melanoma lesion. In each patient approx. 10 MBq of 99mTc Nanocoll in 0.1 mL (Nycomed Amersham Sorin; particle size range, 3-80 nm) was injected intradermally around the MM lesion or surgical scar. Dynamic acquisition was performed for 20 minutes (20 frames/min) and the study was concluded within four hours of injection. Using an external radioactive marker, the skin over the SLN was marked with China ink.

294 SLNs were scintigraphically identified: 117 in the inguinal region, 147 in the axillae, four in the submandibular region, three in the laterocervical region and 23 at other sites. In two patients no drainage was detected. In 43 patients more than one sentinel node was identified. In 13 patients with lesions located in the trunk the tracer drained towards multiple lymph node stations or unexpected lymph nodes (nine cases). Histology and immunohistochemistry diagnosed MM in 25 SLNs; 19 were positive for metastasis with hematoxylin-eosin staining, five with Hmb45 and one with CD68 immunostaining. All 25 detected lymphatic basins were excised. In nine of these basins there was metastatic involvement of at least one other lymph node besides the SLN. During follow-up which ranged from six to 86 months, metastatic disease was found in only one patient with a histologically negative SLN six months after surgery.

This study confirms the utility of scintigraphic SLN detection in patients with MM. In most of the cases the procedure led the surgeon to evaluate the drainage area, which is unpredictable for lesions in the trunk and may be difficult to delineate using only patent blue dye. Furthermore, in approximately 10% of cases we observed dual drainage from individual lesions, mainly those located on the trunk. We will proceed to compare the results obtained during follow-up with those of an investigational group of patients with melanoma who were not subjected to lymphoscintigraphy for SLN detection in order to obtain well-founded information on the prognostic value of this technique.