PSAP serves as a confirmed biomarker in breast cancer with elevated expression linked to poor prognosis, in GC with tissue overexpression associated with advanced stage and adverse outcomes, and in CRC as a CMS4/CRIS-B subtype marker; potential biomarkers to be confirmed, which include its role as a serum staging marker in PCa, an early diagnostic marker in GBC, and a co-diagnostic marker with QSOX1 in mesothelioma. The gene discussed is PSAP; the disease is colorectal carcinoma.