Immune checkpoint inhibitors produce impressive clinical benefits in cancer types previously considered untreatable, such as metastatic melanoma. However, only some patients benefit from the treatment, for reasons that remain largely unknown. By conducting a large reanalysis of bulk and single-cell RNA sequencing data we uncovered that a specific population of FDCSP+ fibroblasts might predict response to cancer immunotherapy independently of T cells, B cells or tumour mutational burden, thus opening new avenues to explain why some patients do not respond to immune checkpoint inhibitors.