MS4A1 and rheumatoid arthritis: Results showed marked enrichment in exhausted CD8+ T cells and macrophages within the TME of C-MPNSTs as supported by LAG3, CD68 and CD163 overexpression, in contrast to a predominance of mast cells encountered in the TME of SCMs with overexpression of MS4A (MS4A1 and MS4A2), CPA3 and STAT4. Furthermore, GSEA identified a significant upregulation of the “Rheumatoid arthritis” gene set in C-MPNSTs.