In situ immunofluorescence and/or FACS analyses of clinical samples from CRC patients revealed that TMEM123 is mostly enriched in CD8+ and CD4+ T cells of the immune infiltrates present in primary and metastatic cancers, being simultaneously expressed in synchronous and metachronous metastasis, while it is expressed at much lower level in T cells resident in proximal normal tissues, and almost negative in blood-circulating T cells and in non-activated or exhausted T lymphocytes. The gene discussed is TMEM123; the disease is metastatic malignant neoplasm.