Background：GCDFP-15(gross cystic disease fluid protein 15), also known as PIP(prolactin-induced protein) is a secretory glycoprotein expressed in benign and malignant breast tumor tissues and in some normal exocrine organs such as sweat, salivary, and lacrimal glands(PMID: 12393800). GCDFP-15 expression is increased by prolactin and androgen and inhibited by estrogen(PMID: 18854942). The expression is also regulated by interleukins. GCDFP-15 is a marker of apocrine differentiation and is frequently used for assessment of metastases or regional recurrences of breast origin.
