Nonvisualized sentinel lymph nodes on lymphoscintigraphy in melanoma: predictive factors and surgical outcomes

Preoperative lymphoscintigraphy is the standard for the identification of sentinel lymph nodes (SLNs) in melanoma. The impact of negative scintigraphy [nonvisualization (NV) of the SLN] on surgical outcomes is inadequately reported in the literature. The objectives of this study were to determine the incidence, predictive factors, and surgical outcomes of NV in clinically node-negative melanoma patients.

A retrospective review of a prospective, Institutional Review Board approved, melanoma sentinel node database from January 2005 to August 2015 was performed.

Twenty-seven of the 897 (3%) patients had negative scintigraphy. Single-photon emission computed tomography/computed tomography was performed in addition to planar imaging in four patients and failed to locate the SLN in all cases. NV was associated with older age (71 vs. 59 years, P<0.001), head and neck primaries (41%), and previous operations adjacent to the primary tumor or nodal beds (37%). NV was not associated with sex, BMI, or T stage. Despite a negative scintigram, the SLN was still found at operation in 10 of the 27 (37%) patients using the hand-held gamma probe, with one (10%) patient having nodal metastasis. Two patients with NV had nodal recurrence, with a mean follow-up of 3 years.

Preoperative lymphoscintigraphy in clinically node-negative melanoma patients is associated with a low NV rate. Predictors for NV include age, head and neck location, and previous operations at adjacent sites. NV should not preclude surgical exploration as the SLN can still be found at operation in over one-third of patients.