Clinical Case of Primary Ovarian Osteosarcoma.

We describe an extremely rare clinical case of primary ovarian osteosarcoma (OS) in a 70-year-old woman, along with the diagnostic criteria for this condition. The patient underwent chemotherapy and has been under observation for 27 months. Currently, tumor progression with metastatic lesions of the peritoneum is observed. This case highlights the importance of further studies of primary ovarian OS. Ovarian OS is not included in the 2022 WhO classification of genital tumors, but such cases occur; their diagnosis is difficult, and there is no consensus on the treatment. Accumulat- ing data on the structural features of these tumors and their response to treatment will help improve the understanding of their treatment.