OBJECTIVES. To determine a number of diagnosed breast carcinomas in a two-year period. To determine a frequency of breast carcinomas according to a phenotype. To compare the presence of certain histological types with reference to the phenotype of breast carcinomas. STUDY DESIGN. A retrospective comparative study. PARTICIPANTS AND METHODS. The study includes 363 newly discovered ductal in situ breast carcinomas (DCIS) and invasive breast carcinomas diagnosed at the Clinical Institute for Pathology and Forensic Medicine at the Clinical Hospital Centre Osijek. By applying the method of immunohistochemistry, estrogen, progesterone, HER-2/neu and Ki-67 were determined. In order to immunohistochemically process tissues, the automatic counter Ventana BenchMark Ultra, produced by the company Roche, and monoclonal primal antibodies of the company Roche, made for the laboratory use, were used. RESULTS. In the period from January 2015 until December 2016, 342 invasive breast carcinomas were diagnosed at the Clinical Institute for Pathology and Forensic Medicine at the Clinical Hospital Centre Osijek. The majority of the examinees were at the age of 60 to 90 (31.58%) with the average age of 61.6 years. According to the histological type, the most frequent invasive breast carcinomas were ductal invasive carcinomas (87.43%). Furthermore, according to the phenotype, the most frequent was luminal B HER negative phenotype (48.54%). Ductal (48.16%) and lobular (52.94%) invasive breast carcinomas and mixed (75%) carcinomas were frequently luminal B of the negative type. Medullary carcinomas (75%) as well as mucinous carcinoma were mostly of the triple negative phenotype. CONCLUSION. In order to diagnose invasive breast carcinomas, the immunohistochemical treatment of a tissue is indispensable. It aims to determine the exact phenotype of carcinomas consequently determining the adequate therapy.