Lee CC et al. (2008) Improved survival after lymphadenectomy for nodal metastasis from an unknown primary melanoma. J Clin Oncol 26: 535–541

Studies examining the prognostic significance of melanoma of unknown primary (MUP) have produced inconsistent results and it is unclear whether patients with MUP require more-aggressive management than patients with known primary melanoma (MKP). Now, Lee et al. have commented that they have conducted the largest ever review of the outcomes of patients with MUP and palpable regional metastasis in a single lymphatic basin, to determine survival rates and prognostic factors.

By examining the clinical records of the 13,000 patients registered on the John Wayne Cancer Institute melanoma database, the researchers identified 1,571 patients with nodal melanoma who underwent regional lymphadenectomy within 3 months of presentation. Among this study group, 262 patients had MUP and 1,309 had MKP. Multivariate analysis revealed that male sex, age ≥60 years, more than one tumor-involved node, decade of diagnosis, and MKP were all associated with a worse prognosis. The researchers then identified 221 pairs of patients (each comprising one patient with MUP and one patient with MKP) who were matched by the four significant covariates age, sex, nodal-tumor burden and decade of diagnosis. The 10-year overall survival rate for patients with MUP was 52%, compared with 36% for the matched patients with MKP (P = 0.0006 for trend). In addition, patients with MUP had a longer median overall survival than patients with MKP (165 months vs 34 months; P = 0.0006).

The authors conclude that lymphadenectomy should be standard initial treatment for MUP with palpable nodal metastasis limited to a single lymphatic basin; however, they highlight the importance of an accurate staging work-up to rule out the possibility of distant disease.