CD103+ T Lymphocyte Count Linked to the Thickness of Invasion on Acral Melanoma without E-Cadherin Involvement

The Roles of Vitamin D Receptor (VDR) and CD8+ T-Lymphocytes in Acral and Mucosal Melanoma Invasion Depth

BACKGROUND

Acral and mucosal melanomas, the most common sun-shielded site melanoma subtypes in Asia and Indonesia, often yield poor prognoses. The invasion depth reflects their progressivity, and the pathogenesis is influenced by vitamin D receptor (VDR) status and CD8+ T-Lymphocyte amount. This study aims to determine the association between the invasion depth of acral and mucosal melanomas with their VDR and CD8+ immunoexpression.

METHODS

A cross-sectional observational study was conducted on 60 formalin-fixed paraffin-embedded (FPPE) samples, with equal representation in acral and mucosal melanoma groups from 2017 to 2021. The samples were assessed for the invasion depth and immunoexpression of VDR and CD8+. A chi-square test with an alternative Exact-Fisher analysis was used to determine the association between the variables in both subtype groups.

RESULTS

An association between VDR and CD8+ immunoexpression and invasion depth in acral melanoma (p value = 0.0001 and 0.009, respectively) was observed, while only VDR immunoexpression was associated with the invasion depth in mucosal melanoma (p-value =0.004). Interestingly, no association was found between CD8+ immunoexpression and the invasion depth in mucosal melanoma (p = 0.640).

CONCLUSION

The role of VDR and CD8+ T-lymphocytes are inversely associated with melanoma depth in acral melanoma, while only VDR is associated with melanoma depth in mucosal melanoma.

Clinical features, molecular pathology, and immune microenvironmental characteristics of acral melanoma

Acral melanoma (AM) has unique biology as an aggressive subtype of melanoma. It is a common subtype of melanoma in races with darker skin tones usually diagnosed at a later stage, thereby presenting a worse prognosis compared to cutaneous melanoma. The pathogenesis of acral melanoma differs from cutaneous melanoma, and trauma promotes its development. Compared to cutaneous melanomas, acral melanomas have a significantly lighter mutational burden with more copy number variants. Most acral melanomas are classified as triple wild-type. In contrast to cutaneous melanomas, acral melanomas have a suppressive immune microenvironment. Herein, we reviewed the clinical features, genetic variants, and immune microenvironmental characteristics of limbic melanomas to summarise their unique features.