Pigmentation in the sentinel node correlates with increased sentinel node tumor burden in melanoma patients

The prognosis of sentinel node (SN)-positive melanoma patients is predicted by a number of characteristics such as size and site of the metastases in the SN. The pathway and prognosis of strong pigmentation of melanoma metastases in the SN is unclear. The aim of this study is to evaluate the role of pigmentation and growth pattern of metastases in the SN with respect to survival. A total of 389 patients underwent an SN procedure (1997-2011). Ninety-five patients had a positive SN and material from 75 patients was available for review. The median follow-up time was 75 months (range 6-164). Pigmentation was scored from 0 to 2 using the following scale: 0=absent, 1=slight, and 2=strong. Growth pattern was scored as either eccentric (1) or infiltrative (2). SN tumor burden was measured according to the Rotterdam criteria. The primary melanoma had a median Breslow thickness of 2.90 mm (0.8-12.00 mm). Ulceration was present in 34 patients (45.3%). There was a median SN tumor burden of 0.5 mm (0.05-7.00 mm). In a total of 75 patients, 59 patients (79%) had no pigmentation, 13 patients (17%) had slight pigmentation, and three patients (4%) had strong pigmentation in the SN. Because of the small numbers, the classification was modified to either absent 59 (79%) or present 16 (21%) pigmentation, respectively. The SN tumor burden was significantly higher (P=0.031) for patients with pigmentation. Patients with pigmentation had a 5-year melanoma-specific survival (MSS) of 47% and a 10-year MSS of 33%. Patients without pigmentation had a 5-year MSS of 70% and a 10-year MSS of 59% (P=0.06). There was no difference in MSS for patients with an eccentric or an infiltrative growth pattern, nor did it correlate with other prognostic factors. Multivariate analysis for MSS showed five significant factors associated with worse prognosis: male sex (P=0.036), nodular melanoma (P=0.001), truncal site (P=0.0001), SN tumor burden more than 1.0 mm (P=0.022), and positive completion lymph node dissection (P=0.004). The 5-year MSS for SN tumor burden is 94% for 0.1 mm or less, 66% for 0.1-1.0 mm, and 41% for more than >1.0 mm (P<0.001). The 10-year MSS for SN tumor burden is, respectively, 94, 51, and 35% (P<0.001). This preliminary exploratory retrospective study showed that pigmentation within the SN seems to correlate with increased SN tumor burden.