Melanoma without a detectable primary site with metastases to lymph nodes.

Objective: To compare outcomes of patients with clinical nodal melanoma metastases that occurred without a detectable primary tumor (melanoma of unknown primary site; MUP) with those with a known primary site (KPM).

Methods: We included data from 459 consecutive patients treated from 1994 to 2007 with radical therapeutic lymph node dissection (LND; stage IIIB, C) due to clinically palpable and pathologically confirmed lymph node metastases (229 axillary; 230 ilioinguinal). The median follow-up was 49 months.

Results: LND was performed in 59 cases (12.9%; 29 men, 30 women) due to MUP nodal metastases, including 33 axillary (14.4%) and 26 ilioinguinal (11.3%). In the MUP group, the 3- and 5-year survival rates were 48% and 41%, respectively. Similar rates were observed in patients with KPM, even with matched-pair analyses. Established prognostic factors (number of metastatic nodes, p=.005; extracapsular extension of metastases, p=.002) influenced survival in the MUP group. Relapses occurred in 31 (53%) and 299 (74.7%) cases in the MUP and KPM groups, respectively.

Conclusions: Survival rates in the MUP and KPM groups were similar, and the same prognostic factors affected both. Thus, all MUP cases should be treated as standard stage III melanomas.