Lymphoscintigraphy and intraoperative gamma probe-directed sentinel lymph node mapping in patients with malignant melanoma

Background and Purpose: Lymphoscintigraphy has been considered a useful tool for sentinel lymph node (SLN) mapping for malignant melanoma. This study evaluated the usefulness of SLN detection by lymphoscintigraphy and excision with intraoperative gamma probe in Taiwanese patients with malignant melanoma. Methods: Thirty six malignant melanoma patients in clinical stage I and II were enrolled. The Breslow thickness of the primary melanomas was ≤ 1.0 mm in 8 patients, 1.01 to 2.0 mm in 12 patients, 2.01 to 4.0 mm in 9 patients, ≥ 4 mm in 3 patients, and unknown in 4 patients who were transferred from other hospitals and had no nodal or distant metastasis. SLN lymphoscintigraphy was performed with filtered ^99mTc-sulfur colloid. An intraoperative gamma probe was used to identify the SLN for dissection. Results: A total of 44 SLNs were detected in 36 patients, with a mean of 1.22 SLNs per patient. The SLN detection rate by lymphoscintigraphy was 100%. During surgery, 39 of the 44 SLNs (88.6%) in 33 of 36 patients (91.7%) were identified. SLN metastasis was found in 8 of 39 dissected SLNs (20.5%) or in 8 of 36 patients (22.2%). The SLN metastatic rate in the patients with primary melanoma with Breslow thickness ≤ 2.0 mm was 10.0% (2/20), and in patients with Breslow thickness > 2.0 mm was 41.7% (5/12). Conclusions: Lymphoscintigraphy and intraoperative gamma probe are useful in localizing and dissecting SLN in patients with malignant melanoma. SLN mapping changed the clinical stage in 22.2% of melanoma patients.