High negative predictive value of slow lymphatic drainage on metastatic node spread detection in malignant limb and trunk cutaneous melanoma.

Aim: Harvesting of the "sentinel lymph node" (SLN) as identified by lymphoscintigraphy (LSG) is becoming increasingly important in the staging of patients with malignant melanoma. The purpose of the current study was to determine whether the appearance time of the LSG had a prognostic value in predicting metastasis dissemination in thick cutaneous malignant melanoma.

Methods: Between July 1999 and July 2003, 88 consecutive patients with histologically proven melanoma with a Breslow's thickness > 1 mm, without clinical or radiological evidence of lymph node involvement or metastasis, prospectively underwent lymphoscintigraphy with 32 Mbq Tc 99m sulfur colloid prior to sentinel lymphadenectomy with sentinel lymph node (SLN) histological examination.

Results: LSG was performed in 88 patients with limb and trunk melanoma and identified a total of 149 sentinel nodes. Pathological examination revealed lymph node involvement in 21 patients (24%). All positive SLNs were imaged with a scintigraphic appearance time of less than 30 min. With a scintigraphic appearance time greater than 30 min, the negative predictive value (NPV) of spread in the SLN was 100% (27/27)(CI 87-100%).

Conclusion: The strong NPV of LSG in identifying "slow" sentinel lymph nodes in patients with no clinical evidence of lymph node involvement suggests that patients could be spared sentinel lymph node biopsy when LSG detects "slow" sentinel lymph nodes. Another prospective study will be required to confirm that the scintigraphic appearance time of sentinel lymph nodes is an important predictive parameter of metastatic disease in sentinel lymph nodes and consequently might reduce the number of sentinel lymph node biopsies.