PTPRM (protein tyrosine phosphatase receptor type M) is a transmembrane receptor that functions as both a cell adhesion molecule and tumor suppressor with context-dependent roles in different tissues. The protein mediates homotypic cell-cell interactions through its extracellular domains, forming stable head-to-tail homodimers between adjacent cell membranes 1. As a phosphatase, PTPRM regulates cellular signaling by dephosphorylating target proteins including members of the protein tyrosine phosphatase family such as PTPN22, thereby modulating PKD-associated pathways including ERK, mTOR, and STAT3 2. PTPRM exhibits tumor suppressive properties in several cancers, with expression significantly decreased in epithelial ovarian cancer correlating with poor prognosis and advanced disease stages 3. Similarly, PTPRM loss through chr18 deletion and promoter hypermethylation contributes to colorectal adenoma-carcinoma progression 4. The gene is also subject to epigenetic silencing in lymphoma development 5 and spermatogonia, where BMI1-mediated repression of PTPRM promotes cell proliferation 6. Paradoxically, PTPRM shows oncogenic properties in cervical cancer, where high expression promotes tumor growth and lymph node metastasis through epithelial-mesenchymal transition 7.