GCDFP15

GCDFP-15 stands for Gross Cystic Disease Fluid Protein 15. It is a small secreted glycoprotein, also known as prolactin-inducible protein (PIP). The protein is produced by secretory cells in the breast and in other exocrine glands, including sweat and salivary glands. It was first identified in nipple fluid from patients with fibrocystic breast changes and has since been used as a histopathological marker.

The biological role of GCDFP-15/PIP is not fully understood, but it is thought to participate in immune defense and to be hormonally regulated by prolactin. The protein is secreted into breast secretions and can be detected by antibodies in tissue sections.

In clinical practice, GCDFP-15 immunostaining is used to help determine whether a metastatic carcinoma originates in the breast. It is often used together with other breast-associated markers such as mammaglobin A and cytokeratin profiles. The frequency of GCDFP-15 positivity in breast carcinomas varies by subtype; many tumors are GCDFP-15 negative, so a negative result does not exclude a breast origin. Positive staining supports but does not prove a breast origin.

Because GCDFP-15 is not entirely specific to breast tissue and can be expressed in skin adnexal tumors, interpretation is contextual and is integrated with morphologic findings and other markers.