BACKGROUND Numerous studies confirm the benefits of using core-needle biopsy (CNB) for diagnosing patients with suspected breast cancer, thus reducing the costs and the stress, and allowing optimum treatment planning. The present study examined the number of patients in Poland who had been diagnosed with breast cancer through inpatient open surgical biopsy (OSB) and CNB by province. MATERIAL AND METHODS This retrospective study used a health needs map to identify patients in 2014 and partially in 2015 who had had OSB or CNB of the breast performed on an inpatient basis due to benign breast lesions and whose diagnosis had been changed from benign to malignant. RESULTS Among the total number of hospitalizations (13 718 cases with OSB) due to benign lesions of the breast, 1506 patients had their diagnosis changed to malignant, constituting 8.59% of new breast cancer diagnoses across the country. The resulting diagnosis change from benign to malignant varied significantly across provinces, from 5.3% to 23.4%. Among the total of 7205 hospitalizations in 2014 with CNB performed using different methods, there were 1574 malignancies, amounting to 8.9% of new diagnoses in Poland. The use of inpatient CNB to diagnose breast cancer differed significantly across provinces, from 0.6% to 34.4%. CONCLUSIONS OSBs are too often used to diagnose focal lesions in breast glands in Poland. In some regions, CNBs are too frequently performed on an inpatient rather than outpatient basis, thereby requiring an analysis of the quality of and access to modern diagnostic methods.