The study is a retrospective review of 407 female patients with primary breast cancer and 320 female patients with benign breast changes who were surgically treated in the University Hospital for Tumors during calendar year 2009. We investigated a possible link between the ABO blood group and breast cancer. All patients had their blood group (ABO antigen and RhD) determined, as a part of preoperative treatment, at the Department for Transfusion Medicine of the University Hospital for Tumors. Erythrocyte antigens were determined using the plate and microcard technique. The mean age of all patients was 62.1 years (range 30 – 95 yrs). No statistically significant differences were found between patients who have cancer and those who have not in the frequency of certain blood groups (χ = 2.525, df = 3, p = 0.471). Also, there was no statistically significant difference between patients with cancer and those without cancer in the frequency of Rh (χ = 2.343, df = 1, p = 0.076). We found a statistically significant but slight correlation between Rh factor and HER2/neu (p=0.038), r=0.106. According to the correlation coefficient, the correlation between these two variables is none or slight. The causal relationship between the two parameters remains unknown and should be tested in a larger study.Ispitivanje je retrospektivno obuhvatilo 407 bolesnica s primarnim rakom dojke i 320 bolesnica s dobroćudnim promjenama u dojci koje su kirurški liječene u Klinici za tumore u 2009. godini. Proučavali smo moguću povezanost između ABO krvne grupe i raka dojke. Krvna grupa (ABO antigen i RhD) utvrđena je svim bolesnicama u okviru prijeoperacijske obrade u Službi za transfuzijsku medicinu Klinike za tumore. Antigeni na površini eritrocita određivani su na pločama i u mikrokarticama. Prosječna dob bolesnica iznosila je 62;1 godina (raspon 30 – 95 godina). S obzirom na učestalost određenih krvnih grupa nisu utvrđene statistički značajne razlike između bolesnica koje imaju rak i onih koje ga nemaju (χ = 2;525; df = 3; p = 0;471). Statistički značajnih razlika u učestalosti Rh faktora između bolesnica s rakom i onih koje ga nemaju; također; nije bilo (χ = 2;343; df = 1; p = 0;076). Otkrivena je statistički znakovita; iako slaba korelaciju između Rh faktora i HER2/neu (p=0;038); r=0;106. Prema koeficijentu korelacije između te dvije varijable korelacije ili nema ili je slaba. Uzročna povezanost između ta dva parametra i dalje je nepoznata i treba je ispitati na većem uzorku
