Spatial Distribution and Phenotypic Profiling of Cd68⁺ and Cd163⁺ Macrophages in Melanoma Progression: Insights into...

Background: Macrophages are key components of the tumor microenvironment and play a critical role in melanoma progression. However, the dynamics of different macrophage subsets, particularly CD68⁺ and CD163⁺ populations, in relation to tumor thickness and stage remain insufficiently characterized. Objective: This study aimed to quantitatively assess intratumoral and peritumoral CD68⁺ and CD163⁺ macrophages in cutaneous melanoma and to investigate their associations with Breslow thickness, pT stage, and AJCC stage. Methods: We conducted a retrospective cohort study of 126 patients with cutaneous melanoma (AJCC stages IA-IIID). Tumor samples were examined histologically and immunohistochemically for CD68⁺ and CD163⁺ macrophages, and quantitative analysis was performed in intratumoral and peritumoral regions. Results: This study included 126 patients with cutaneous melanoma, ranging in stage from IA to IIID. Histopathological analysis revealed that melanoma tissues were primarily composed of irregular clusters of atypical melanocytic cells infiltrating the dermis and subcutaneous fat. Immunohistochemical staining identified CD68⁺ and CD163⁺ macrophages both within the tumor and in the surrounding stroma. Macrophage infiltration significantly increased with tumor thickness (Breslow) and progression to more advanced stages. Specifically, at Breslow thickness <1.0 mm, the mean number of CD68⁺ macrophages in the intratumoral zone was 29.7 ± 4.3 cells, increasing to 70.3 ± 6.4 cells in tumors >4.0 mm. CD163⁺ macrophages showed similar trends, with a rise from 15.6 ± 2.8 cells at <1.0 mm to 39.8 ± 4.6 cells at >4.0 mm in the intratumoral zone. Additionally, macrophage density was higher in tumors with ulceration, and both CD68⁺ and CD163⁺ macrophage numbers increased progressively with tumor stage, particularly in advanced stages. The number of CD68⁺ macrophages at stage IA in the intratumoral zone was 21.6 ± 3.1 cells and increased to 56.4 ± 6.8 cells at stage IIID, while CD163⁺ macrophages rose from 13.8 ± 3.2 cells at stage IA to 36.4 ± 4.6 cells at stage IIID. This suggests that macrophage infiltration, particularly CD163⁺ cells, correlates with melanoma progression. Conclusions: Our findings highlight distinct spatial and phenotypic patterns of macrophage infiltration in melanoma progression. The prominent increase in CD68⁺ and CD163⁺macrophages suggests their important role in tumor-associated immunomodulation. Further studies are warranted to elucidate macrophage polarization states and their prognostic and therapeutic implications in melanoma.