Regressing thin cutaneous malignant melanomas (< or = 1.0 mm) are associated with angiogenesis

Abstract

In previous studies, we have shown that angiogenesis is often first noted in cutaneous malignant melanomas (CMMs) under 1.0 mm in thickness. Because angiogenesis may signal a more aggressive tumor phenotype, it is important to establish the circumstances associated with onset of angiogenesis. In the present study, we have quantified tumor vascularity in a series of CMMs under 1.0 mm in thickness and either associated with or lacking histologic regression. Microvessels were identified with the lectin Ulex europaeus agglutinin I and the vessels in five fields counted within an ocular grid (area 7.84 x 10(-2) mm2) at 400 x magnification. CMMs (mean 0.48 mm) with regression had greater microvessel counts (27.2 +/- 5.1) compared with CMMs (mean 0.61 mm) without regression (mean 20.1 +/- 7.9) (P < 0.01). However, of particular interest, CMMs in the radial growth phase only and associated with regression (mean 0.40 mm) had strikingly greater vascularity (mean 28.7 +/- 6.9) versus radial growth phase CMMs (mean 0.44 mm) lacking regression (mean 16.4 +/- 6.6) (P = 0.0013). CMMs in the vertical growth phase (mean 0.81 mm) without regression had slightly less vascularity (mean 24.4 +/- 7.3) compared with vertical growth phase CMMs with regression (mean microvessels 27.2 +/- 5.1) (P = 0.1878) but significantly greater microvessels versus radial growth phase CMMs without regression (P = 0.0213). These results suggest that the onset of angiogenesis in thin CMMs is related to at least two phenomena: 1) inflammatory regression and 2) development of the vertical growth phase.