A Study of p63 Immunohistochemical Expression in Benign and Malignant Breast Lesions at a Tertiary Hospital in South India

Introduction Breast cancer is one of the leading causes of cancer deaths in female patients. Breast lesions can have various morphological diversities, ranging from benign to in situ to malignant. An important histopathological feature that distinguishes benign and malignant lesions is the presence or absence of the myoepithelial cell layer. The tumor protein p63 has been characterized as a reliable immunohistochemical marker and is uniquely displayed in the myoepithelial cells of breast parenchyma. Hence, it helps distinguish benign from malignant lesions. Aim To study the value of the immunohistochemical expression of p63 in the diagnosis of breast lesions, to investigate p63 expression in benign and malignant breast lesions, and to assess if loss of p63 expression is consistently associated with invasive disease. Materials and methods About 98 cases of breast disease were studied, of which 86 were subjected to immunohistochemical staining for p63 and analyzed for its expression, and the staining arrangement was interpreted. Results Out of 86 cases, there were 46 benign and 40 malignant breast lesions. Immunohistochemical staining for p63 in the benign lesions showed continuous positivity with a score of three in 30 cases and discontinuous positivity with a score of two in 16 cases. In malignant lesions, p63 was not expressed and scored zero in 35 cases and discontinuous positive with a score of one in five cases. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of p63 in distinguishing the benign from the malignant lesions was 100%, 87.50%, 90.20%, 100%, and 94.19% respectively. Conclusion There is a statistically significant difference in the expression of p63, a specific nuclear marker for myoepithelial cells, in benign and malignant breast lesions. It was consistently positive in benign breast lesions and negative in the majority of malignant breast lesions. Thus, p63 can act as a helpful immunohistochemical marker in categorizing histopathologically-difficult cases into benign or malignant ones.