PIWIL4 and colorectal carcinoma: In this context, aberrant expression of PIWI proteins, especially PIWIL2, has been documented in a wide range of tumors, including colorectal carcinoma, gastric cancer, prostate cancer, breast cancer, gliomas, soft tissue sarcomas, cervical cancer, and hepatocellular carcinoma [50,88,89,90,91,92,93,94,95].