Embryonic vasculogenesis in nodular melanomas and tumour differentiation

Area of Science:

• Oncology
• Pathology
• Cancer Biology

Background:

• Vasculogenic mimicry (VM) and incorporated microvasculature (INC) are two distinct vascularization pathways in tumors.
• The role of pigment in regulating these vascularization strategies in cutaneous melanoma remains unclear.

Purpose of the Study:

• To investigate the relationship between pigment levels and the prevalence of VM versus INC in nodular vertical growth phase (VGP) cutaneous melanomas.
• To assess the potential association of VM with aggressive tumor characteristics.

Main Methods:

• Analysis of 27 cutaneous melanoma tumors (15 pigmented, 12 amelanotic), sampling 10 nodules each.
• Histological assessment using HE, Reticulin, and PAS staining for vascular patterns.
• Immunohistochemistry (HMB45, LN5, α(5)β(1) integrin) and electron microscopy to characterize vascular and cellular components.

Main Results:

• Amelanotic melanomas predominantly exhibit VM, characterized by tumor cells forming vascular-like spaces.
• Pigmented melanomas show a higher proportion of INC derived from pre-existing stromal vessels.
• Tumor cells lining VM spaces express LN5 and α(5)β(1) integrin, indicating a potential switch to a more aggressive phenotype.

Conclusions:

• Pigmentation is negatively correlated with VM and positively with INC in cutaneous melanoma.
• Amelanotic melanomas utilize embryonic VM more significantly than pigmented melanomas.
• VM is associated with markers suggesting increased aggressiveness in melanoma.