DPYSL2 and vitamin D deficiency: This study aimed to determine whether selected markers—lipoprotein-associated phospholipase A2 (Lp-PLA2), dihydropyrimidinase-like 2 (DPYSL2), and 8-hydroxy-2′-deoxyguanosine (8-OHdG)—can differentiate specific types of brain tumors in patients with vitamin D deficiency, i.e., whether these markers have diagnostic significance in oncology.