The biology and prognostic value of lymphatic vessel density (LD) and lymphatic invasion (LI) in regression in melanoma

Abstract

9017 Background: Regression in melanoma is characterized by increased vascularity, lymphocytic infiltrate and fibroplasia in the papillary dermis, accompanied by the absence (complete regression, CoR) or presence (partial regression, PaR) of melanoma cells in the epidermis. The prognostic value of regression is controversial. We noticed that LD and LI were increased in the areas of regression (AR) or areas with brisk lymphocytic infiltration (AB). Our goal was to clarify the prognostic value of regression in melanoma. Methods: Dual immunohistochemical staining was done using antibodies to podoplanin (lymphatic vessels) and S100 (melanoma cells) on paraffin tissues from 321 patients with vertical growth phase (VGP) primary melanomas who had 10 years or more of follow-up. LD in AR (both CoR and PaR) was compared with that of normal dermis adjacent and distant, as well as LD in the AB. LI in these areas was also scored. Unadjusted and adjusted hazard rates were obtained from univariate and multivariate Cox models for time to melanoma-specific death using established melanoma prognostic factors. Results: 116 patients (36%) had regression: 75 CoR (23%) and 41 PaR (13%). LD significantly decreased stepwise from CoR (mean ± se, 23.7 ± 2.7) to PaR (15.5 ± 1.1), adjacent normal dermis (7.3 ± 0.28) and distant normal dermis (5.4±0.31) and it was significantly elevated in the AB (18.5±0.78). Melanomas with CoR had the highest percentage of LI in both AR and AB. In addition, the percentage of LI in AB was highest for men and for those with VGP tumor infiltrating lymphocytes (TILs). Both high LD in AR and more LI in AB were associated with poor prognosis (p=0.004 and p=0.002, respectively). Six factors were significant in the final multivariate model: LI in AB (HR=2.3), LD in AR (HR=1.04), thickness (HR=1.44), axial (HR=7.7), ulceration (HR=2.5) and no VGP TILs (HR=2.8). Conclusions: AR and AB were associated with increased LD and higher incidence of LI in primary melanomas. LD and LI in AR or AB are independent prognostic factors. Our data suggest that the effects of regression on prognosis are mediated at least in part through lymphangiogenesis and LI. No significant financial relationships to disclose.