Introduction Sentinel lymph node biopsy (SLNB) is considered the gold standard for evaluating locoregional spread in patients with cutaneous malignant melanoma (MM). Since the status of regional lymph nodes is a key prognostic factor, microscopic lymph node involvement has been added by AJCC in the N-category in tumor staging (2009). Our study focuses on the correlation between Breslow depth of MM and the probability of metastases in the Sentinel lymph node; moreover, it analyses the rates of recurrent/metastatic disease and mortality among patients with positive SLNB compared with those with negative SLNB.
Methods From 2000 to 2007 SLNB was performed on 257 consecutive patients, preceded by lymphoscinigraphy with 99mTc Nanocoll. Patients were divided in three groups according to Breslow thickness: Group A (54 patients; Breslow <1 mm), Group B (168 patients; 1 mm≤Breslow<4 mm) and Group C (25 patients; Breslow≥4 mm). In 10 patients Breslow thickness couldn’t be consistently evaluated. Follow-up was performed every three/four months for two to nine years with clinical examination and ultrasound (eventually chest X-ray, CT or PET). Fisher's exact and Chi-square tests were used to compare the incidence of recurrent/metastatic disease and mortality among SLNB-positive and -negative patients.
Results SLNB resulted positive in 6/54 (11,1%) patients of Group A; those with positive SLNB had a higher rate of recurrent or metastatic disease (50%, P=0.05) and mortality (33,3%, P=0.06) compared with those with negative SLNBs (14.6% and 4.2% respectively). In Group B, 34/168 (20,2%) patients resulted having SLN involvement. Thirteen of them (38,2%) had a recurrence or metastases and 7 (20,5%) died, compared with an incidence of secondary events and mortality of 38,2% (22/134) and 20,5% (7/134) respectively in SLNB-negative patients, with a significant difference between the two groups (P<0,01). In Group C, SNLB was positive in 18/25 (72%) patients; the respective rates of recurrence of disease/metastases and mortality in SLNBs-positive and -negative patients were 55,5% (10/18), 22,2% (4/18) and 28,5% (2/7), 0% (0/7) respectively, with no significant differences among the two groups.
Discussion Our experience confirms the positive correlation between Breslow depth of MM and the probability of SLN involvement; moreover, it shows that SLN status is an important prognostic indicator in patients with Breslow <4 mm, affecting the risk of secondary events and the survival as well.