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P63 and cytokeratin8/18 expression in breast, atypical ductal hyperplasia, ductal carcinoma in situ and invasive duct carcinoma.

Background and Purpose : The pattern and distribution of p63 expression as a myoepithelial/basal stem cell marker can be different between atypical ductal hyperplasia (ADH), ductal carcinoma in situ (DCIS) and invasive ductal carcinoma (IDC) and may denote basal phenotype of breast ductal carcinoma. CK8/18 is a luminal marker and may indicate a luminal phenotype of IDC and its expression in ADH and DCIS may refer to a possible precursor lesion to IDC. This work was designed to study and compare the expression of p63 and cytokeratin 8/18 (CK8/18) in some cases of ADH, DCIS and IDC. Materials and Methods : Histopathological evaluation and immunohistochemical study of anti-p63 and anti- CK8/18 was performed on selected archival cases of 7 ADH, 12 DCIS, 30 IDC of known clinicopathological data and previous estrogen receptor status (ER) for IDC. Confirmatory anti-smooth muscle actin (ASMA) expression for positive p63 cases was performed. Results : p63 was expressed in the peripheral rim of the myoepithelial cell layer in ADH and DCIS with occasional gabs in DCIS. It was positive and stained occasional malignant cells in 3/30 (10%) of IDC cases. Confirmatory ASMA staining decorated the same peripheral rim of cells in ADH and DCIS, but was negative in p63 positive IDC cases. CK8/18 was positive in 100% of ADH, 8/12 (66.7%) of DCIS and 22/30 (73%) of IDC cases. Combined p63 and CK8/18 expression was noticed in 3/30 (10%) of IDC. Conclusion : It is concluded from this study that p63 is specific and valuable in differentiating myoepithelial cells and is more specific and valuable than other myoepithelial markers, as ASMA and can differentiate between ADH, DCIS, IDC as it stains peripheral myoepithelial cells in ADH and DCIS with gabs in the latter and does not stain any neoplastic cells. In IDC, it is positive in malignant cells in a minority of cases which may indicate basal/stem cell/myoepithelial cell origin of breast carcinoma. Comparatively, CK8/18 cannot differentiate ADH, DCIS and IDC as there is no difference in its staining pattern among them, which may suggest that they are a continuum or that ADH and DCIS are precursors for the luminal phenotype of IDC. Key Words : p63 -CK8/18 -IDC -ADH -DCIS -Basal/ stem cells.