Table 2 A key summary of the immune microenvironment in acral melanoma

Yoshiyuki Nakamura

Retrospective study

CM (n = 53)

AM (n = 65)

Immunohistochemistry

The total TIL count was significantly lower in ALM than in CM (54.2 vs. 72.9, p < 0.01)

The CD8 TIL count was significantly lower in ALM than in CM (33.0 vs. 46.5, p < 0.01)

[84]

Jiannong Li

Retrospective study

AM (n = 8);

GSE115978 (n = 32);

GSE72056 (n = 19)

TCGA:

AM(n = 336);

CM(n = 443)

scRNA-seq

Compared to the non-AM dataset (GSE115978 and GSE72056), acral melanomas had significantly fewer PDCs, CD8 T cells, and NK cells, very few γδ T cells, and a lower mean immune infiltration rate (39.1% vs. 71.2% vs. 67.6)

Further validation of the TCGA dataset revealed that the proportion of CD8T effector memory cells, NK cells, and γδ T cells were lower in AM patients than in those with CM

[80]

Miguel Zúñiga-Castillo

Retrospective study

ALM (n = 67);

SSM (n = 67)

Immunohistochemistry

Increased M2-Ms in ALM compared to SSM

[85]