The receptor-binding cancer antigen expressed on SiSo cells (RCAS1) is a novel tumor-associated antigen that induces cell-cycle arrest and/or apoptosis in RCAS1 receptor-bearing human cells. Current evidence has revealed enhanced RCAS1 expression in the tumor malignant stage of several organs, which may play a crucial role in tumor progression by enabling cancer cells to evade immune surveillance. In the last few years, tissue RCAS1 protein expression and circulating levels in biofluids have further been the focus of extensive research as a diagnostic and prognostic marker in several human malignancies. The present article aimed to review the available data so far concerning the clinical significance of RCAS1 in human neoplasia. Reviewing of English literature revealed that tissue RCAS1 expression was associated with important clinicopathological parameters for patients' management and prognosis, being considered as an informative biomarker in several types of human malignancy. In addition, the current evidence supported a crucial role for RCAS1 in tumor immune escape, which renders this receptor a promising target for future (gene) therapeutic approaches. However, the clinical application of circulating RCAS1 concentrations in biofluids as a marker in the management and prognosis of tumor malignancies needs to be further explored, since the data so far are still extremely limited.