Ovarian cancer is one of the most common causes of death in the female population. Among malignant tumors, ovarian cancer ranks fourth after neoplasms of the body, cervix, and mammary gland. High mortality rates in malignant ovarian neoplasms are primarily due to the asymptomatic course, the ineffectiveness of screening diagnostic methods, and the progression of the tumor process. One of the clinical and morphological features of ovarian cancer is pathological biomineralization. The purpose of the work is to establish the morphological features and phase composition of pathological biominerals. Also to investigate the potential diagnostic value of mineral formations of ovarian cancer. We have analyzed 60 samples of ovarian cancer by histopathology (hematoxylin-eosin and von Kossa staining), immunohistochemistry, scanning electron microscopy with EDX and transmission electron microscopy. Results. We detected hyperechoic formations of a rounded shape with smooth edges and precise contours during the ultrasound diagnosis of ovarian cancer. The size ranged from 2 to 5 mm. Histological analysis demonstrated the presence of psammoma bodies (Pbs) in the tumor tissue of the ovary with a variation in the amount from 1 to 200 units. PBs were mainly localized at the base of papillary growths of ovarian serous carcinoma and tumor tissue detritus. The sizes of these formations varied from 12.6 to 493.7 μm. Psammoma bodies and their fragments in the tumor tissue were stained black with von Kossa staining. This indicates the presence of calcium phosphate salts in the composition of these bodies. Immunohistochemical examination of ovarian cancer tissue demonstrated the accumulation of OPN and OC on the surface of mineral formations. This indicates the presence of hydroxyapatite and proteins in the structural composition of PBs. Scanning electron microscopy established that the calcifications have different sizes, rounded shapes, and fragile structures. The main lines of Ca and P were present in the EDX spectra. Their intensity ratio reflects the characteristic features of hydroxyapatite Ca10(PO4)6(OH)2. Transmission electron microscopy demonstrated the poly- and monodispersity of apatite crystals. The electron diffraction (ED) pattern indicates the polycrystalline nature of these mineral inclusions. Crystalline particles ranged in size from 5 to 15 nm to 40 to 50 nm, which illustrates the polydisperse morphology of nanosized crystals of the pathological deposit. Therefore, studying the structure, physicochemical, and phase composition of ovarian cancer calcifications, and their imaging features is essential because of the possible practical application of this pathological phenomenon for the early diagnosis of ovarian cancer and other malignant neoplasms with biomineralization. The structural properties of biomineral deposits of tumor tissue make it possible to increase the accuracy of early diagnosis, and the informativeness of the final result at the pre-and postoperative stages, which can improve the prognosis and preserve the quality of life of patients.