The routine immunohistochemical evaluation in Paget disease of the nipple.

Paget disease (PD) of the nipple with coexisting intraductal (DCIS) and invasive carcinoma of the breast comprises 0.6-1.8% of all malignant epithelial neoplasms of this organ. Unlike invasive ductal carcinoma, there are many controversies concerning histological features of PD and the significance of the immunohistochemical characteristics of this neoplasm, which limits the optimal treatment protocols. Therefore, we decided to verify the immunohistochemical markers of PD basing on the retrospective analysis of postoperative material from 69 patients treated surgically. Microscopic examination revealed partial (7 cases) or total (62 cases) replacement of the squamous epithelium of the nipple with nests of atypical glandular cells spreading in an area ranging from 0.2 to 2.5 cm. DCIS coexisting with the PD lesions was present in all examined patients, and infiltrating carcinoma occurred in 31 (44.9%) patients. Both intraepidermal and DCIS components presented c-erbB2 overexpression. Positive estrogen and progesterone receptor staining was observed only in 7 (10.1%) and 2 (2.7%) tumours, respectively. Ki-67 proliferation index of PD cells ranged from 10% to 30%, whereas in DCIS it varied from 4% to 20%. The value of Ki-67 index exceeding 25% in the intraepidermal component of PD was associated with worse overall survival rate.