Purpose: Regional lymph node status is the strongest prognostic determinant in early-stage melanoma. Lymphatic mapping and sentinel lymphadenectomy (LM/SL) is standard to stage regional nodes because it is accurate and minimally morbid, yet its role for thin (<or= 1.5 mm) primary melanomas is unknown.
Patients and methods: Our melanoma database of more than 10,000 patients was reviewed for patients with melanomas <or= 1.50 mm thick who underwent LM/SL. All had lymphoscintigrams and LM/SL via dye alone or with radiopharmaceutical. Patients with tumor-positive sentinel nodes (SNs) underwent completion dissections.
Results: Five hundred twelve patients underwent LM/SL. Most were men (57%), and median age was 49 years. Most primary melanomas were on the torso (44%). Twenty-five patients (4.9%) had tumor-positive SNs. The thinnest lesion with a nodal metastasis was 0.35 mm. The SN-negative and SN-positive cohorts were equivalent by sex, but SN+ patients tended to be younger (P =.053), with significantly more SN metastases in those younger than 44 years (P =.005). No consistent pathology among SN-positive primary melanomas was found. Among those with 1.01- to 1.05-mm primaries, 7.1% were SN-positive. Among 272 patients with lesions <or= 1.00 mm, 2.9% had positive SNs and 1.7% with lesions <or= 0.75 mm had SN metastases. All 13 deaths were in SN-negative patients. Median follow-up durations in SN-positive and SN-negative patients were 25 and 45 months, respectively.
Conclusion: The high nodal positivity rate associated with primary melanomas 1.01 to 1.50 mm thick suggests that LM/SL is indicated in this group. Younger age may be correlated with nodal metastases in patients with lesions <or= 1.00 mm. Lesions <or= 0.75 mm have minimal metastatic potential, and therefore LM/SL is rarely indicated.