Dermal vasculature and melanocytic proliferation index in photodamaged skin in the assessment of lateral margins of lentigo maligna and lentigo maligna melanoma

Lentigo maligna (LM) is the most common subtype of melanoma on the face. When it invades the dermis it is called lentigo maligna melanoma (LMM). Its histological delimitation is controversial due to subjectivity. Analysis of peritumoral vasculature and proliferation index of melanocytes may help to differentiate tumor areas from tumor-free areas, as neoplasia-induced angiogenesis in such scenarios, as well as the higher proliferation index of melanocytes in melanomas, are well established. This work compares the peritumoral vasculature and melanocyte proliferation index of LM and LMM with that of adjacent non-neoplastic skin and sun-damaged skin (control). Forty-three resection cases of LM and LMM were selected retrospectively. Immunohistochemistry was performed for anti-CD31 and anti-CD105 to assess vascularization. Melanocyte proliferation index double labeling was performed using the anti-Melan-A and anti-Ki-67. The Chalkley optical grid was used to quantify blood vessel hotspots. Doubly labeled cells with anti-Melan-A and anti-Ki-67 were counted at tumor, free margin, and control skin. Microvasculature quantification under the melanomas, for both CD31 and CD105, was greater than at the margins of the same specimens (P < 0.0001; P = 0.0001) and greater than control skin (P = 0.0016; P = 0.0027), with higher density for CD31 than CD105. The mean number of double-labeled proliferating melanocytes at the melanoma periphery was greater than at the adjacent free skin and control skin (P = 0.0011). The control skin samples showed the highest CD31-positive vasculature in the head and neck region, with a positive correlation between melanocytic proliferation index and vasculature. The presence of neovascularization (CD105) and proliferating melanocytes (Ki67+/Melan-A+) are suspicious findings for LM/LMM, helping to outline, diagnose, and evaluate tumor margins.