IMMUNOHISTOCHEMICAL LOCALIZATION OF PARATHYROID HORMONE-RELATED PROTEIN IN CANINE MAMMARY-TUMORS

Parathyroid hormone-related protein (PTHrP) was localized immunohistoc hemically in 58 canine mammary tumors (31 malignant, 27 benign) and ad jacent normal or hyperplastic mammary tissue. PTHrP immunoreactivity w as significantly enhanced by pretreatment with microwave heating in no rmal and neoplastic tissues. Epithelial cells of hyperplastic and neop lastic mammary tissues, myoepithelial cells, and metaplastic osteoblas ts in mammary tumors stained moderately to strongly positive for PTHrP . No significant difference between staining intensity for PTHrP and h istologic pattern of mammary tumors was found. The presence of PTHrP i n normal and neoplastic canine mammary tissues supports a pathophysiol ogical role for PTHrP as a paracrine of autocrine hormone in the mamma ry gland.