**Background of PIP Antibodies**
PIP (Prolactin-Inducible Protein) antibodies target a small secreted glycoprotein (~15 kDa) encoded by the *PIP* gene, initially identified for its regulation by prolactin in breast tissue. PIP is expressed in various exocrine glands, including mammary, lacrimal, and salivary glands, and plays roles in cell adhesion, immune modulation, and lipid metabolism. Its overexpression in breast cancer, particularly estrogen receptor-positive (ER+) and low-grade tumors, has made it a biomarker of interest in oncology.
PIP antibodies are widely used in immunohistochemistry (IHC) to detect PIP expression in tissue samples. In clinical diagnostics, they help distinguish breast carcinoma from other malignancies (e.g., lung or ovarian cancers) due to PIP's tissue-specificity. However, PIP expression is not exclusive to cancer; it also occurs in benign conditions like apocrine metaplasia.
Research suggests PIP may influence tumor progression by modulating immune responses or interacting with CD4+ T cells, though its exact mechanistic role remains unclear. Antibodies against PIP also hold potential as tools for studying protein function or developing targeted therapies. Despite limitations in specificity, PIP antibodies remain valuable in pathology for tumor classification and prognostic evaluation, particularly in breast cancer diagnostics.