IntroductionThe most common cancer in women is, by far, breast cancer. The incidence and mortality of breast cancer must be reduced by a multidisciplinary strategy that includes education campaigns, preventive measures, screening programmes for early diagnosis, and the availability of treatment facilities. The use of immunohistochemical (IHC) stains with relative specificity for myoepithelial markers has become a mainstay of standard diagnostic breast pathology because the presence and distribution of myoepithelial cells might differ greatly amongst the distinct breast proliferation. Although it has also been reported that DOG1 is expressed in other mesenchymal tumours, DOG1 has been demonstrated to be sensitive and specific for the detection of gastrointestinal stromal tumors (GISTs). Both myoepithelial cells (MECs) and luminal epithelial cells have occasionally displayed DOG1 immunoreactivity in the breast.Materials and methodsThis prospective cross-sectional study was done in the Department of Pathology at Osmania General Hospital, Hyderabad on 60 cases from June 2017 to June 2019. Female patients with different breast lesions including benign proliferating lesions, ductal carcinoma in-situ (DCIS), and invasive carcinoma breast cases were included in the study. Inflammatory lesions, mesenchymal, and metastatic tumors were excluded. IHC expression of DOG1 as a myoepithelial marker to discriminate invasive from non-invasive breast lesions was evaluated and correlated with clinicopathological features.ResultsThe mean age of the study population was 33.67 ± 8.48 in the benign group and 54.43 ± 12.84 in the malignant group. Fifty percent (15) of the patients with benign lesions belonged to the age group 20-30 years, whereas 26.7% (8) of the patients with malignant lesions belonged to the age group 61-70 years. DOG-1 expression was strongly positive in fibroadenoma, ductal hyperplasia, fibrocystic disease, whereas strongly negative in malignant disease of the breast (p< 0.0001). P63 expression was strongly positive in benign breast diseases and strongly negative in malignant diseases (p< 0.0001).ConclusionDOG1 seems to be similar to p63 as a myoepithelial cell marker both in normal breast tissue and in benign lesions. DOG1 is strongly positive in benign breast diseases and strongly negative in malignant breast diseases. Hence, it can be considered as a useful myoepithelial marker in differentiating invasive breast carcinoma and non-invasive breast lesions.