ABO Blood Groups, Rh Factor, and Thyroid Cancer Risk: To 'B' or Not to 'B'

Purpose: In this study, we aimed to evaluate ABO blood groups and Rh factor in patients with thyroid cancer. Methods: Demographical and clinical features, cytological results, ABO blood groups, and Rh factor status of patients with benign and malignant thyroid disease were evaluated. Histopathological features of thyroid cancer were compared in Rh positive and negative patients, and patients with different ABO blood groups. Results: Histopathological diagnosis was benign in 1,299 (63.5%) and malignant in 744 (36.5%) patients. There was no significant difference between benign and malignant patients in terms of age, sex, thyroid autoantibody positivity, and ABO blood groups (p > .05 for each). A significantly higher rate of patients with malignant disease were Rh positive compared to patients with benign disease (91.8% vs. 88.1%, p = .046). In thyroid cancer patients, extrathyroidal extension and advanced stage (3-4) were observed more frequently in patients with B compared to non-B blood groups (p = .028 and 0.042, respectively). The likelihood of the extrathyroidal extension was 4.272 (95%: 1.816-10.049) times higher in B blood group compared to non-B blood groups in patients with multifocal disease (p < .001). Patients with O blood group had lower rate of capsular invasion than patients with non-O blood groups (p = .018). Conclusion: Patients with B blood group had higher risk of extrathyroidal extension and advanced stage compared to patients with non-B blood group.