P-cadherin as a marker in the differential diagnosis of breast lesions.

AIMS To assess the value of the calcium dependent cell adhesion molecule P-cadherin as a myoepithelial marker in the differential diagnosis of benign and malignant breast lesions. METHODS Immunohistochemical analysis of normal breast, sclerotic breast lesions, tubular carcinomas, and ductal carcinoma in situ using a P-cadherin specific antibody and comparison with smooth muscle actin. RESULTS All myoepithelial cells in normal breast ducts, ductules, and lobules and sclerotic lesions showed strong staining for P-cadherin. There was no staining of tubular carcinomas; myoepithelial cells were demonstrated around in situ carcinomas. Weaker reactivity was seen in a proportion of cells in some hyperplasias and in situ carcinomas. This weak reactivity in these tissues was not seen for smooth muscle actin but in radial scars, tubular carcinomas, and ductal carcinoma in situ staining of stromal cells caused difficulties in the identification of myoepithelial cells. CONCLUSION P-cadherin is a useful marker in the differential diagnosis of breast lesions.