FSTL1 and melanoma: Cross-referencing with the Cell Surface Protein Atlas (CSPA) reduced this to 120 surface-accessible proteins, which were subsequently filtered through the HisgAtlas immunosuppression database to yield 18 candidate biomarkers with documented immunoregulatory functions: APOH, B7-H3 (CD276), CALR, CD26, CD39, CD44, CSF1, FSTL1, GDF15, GPNMB, GRN, ICAM1, L1CAM, MERTK, MICB, MRP2, SMPD-1, and TIMP1 that were detected on melanoma exosomes but absent from melanocyte-derived exosomes in our dataset.