Malignant melanoma (MM) early lymph node (LN) metastasis usually appears first in the sentinel LN (SLN). Breslow thickness is the main factor considered in the selection of patients to be submitted to SLN biopsy. The present study aimed to describe other independent prognostic factors useful in SLN candidate selection. During one year, 94 MM patients (90 primary cutaneous MM with Breslow thickness > or = 0.76 mm, and four cutaneous relapses), were submitted to SLN biopsy in the Melanoma Unit at the Hospital Clinic, Barcelona, Spain. The prognostic factors studied were: Breslow thickness, Clark's level of invasion, mitotic rate, cellular type (small, epithelioid, fusocellular, sarcomatoid), vertical growth phase, regression > 50%, severe vascularization, infiltrate (lymphocytic, plasmocytic), ulceration, neurotropism, intravascular/intraneural invasion, protein p16 expression and recurrence. Nineteen SLN (20.2%) were positive and 75 (79.8%) negative. No positive SLN occurred in MM with Breslow thickness < or = 1.0 mm. Breslow thickness > or = 2 mm (P = 0.005), severe vascularization (P = 0.005), small cell (P = 0.000) and ulceration (P = 0.005) were significant prognostic factors by univariate analysis. Small cell (P = 0.008) and ulceration (P = 0.05) were also significant prognostic factors in a multivariate analysis. The probability of finding a positive SLN for small cell was 56.9% [95% confidence interval (CI), 26.8-82.6%]. The probability of positive SLN for ulceration was 35.5% (95% CI, 14.2-64.7%). For small cell and ulceration together the probability increased to 86.3% (95% CI, 54.3-97.1%). The results of this study corroborated ulceration as a prognostic factor for SLN candidate selection and for the first time we have described small cell melanoma morphology as a significant factor associated with positive SLN.
