Melanoma without a detectable primary site with metastases to lymph nodes

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).

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.

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.

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.