High-grade plasmacytosis of bilateral ovarian malignant tumors refers to its pathological type, and stage IIIC refers to its staging. Ovarian plasmacytoid carcinoma is a relatively common ovarian tumor, mostly bilateral, and can be divided into high-grade and low-grade plasmacytoid carcinoma based on its tumor cell nuclear grade and nuclear division count. High-grade plasmacytoid carcinoma is more common, with high nuclear grade, common nuclear schizophrenia and very poor prognosis. Stage IIIC ovarian cancer refers to the presence of extra-pelvic peritoneal metastases visible to the naked eye, with the largest diameter of the lesion >2 cm, with or without retroperitoneal lymph node metastasis (including tumor spread to the liver peritoneum and spleen, but not metastasized to the parenchyma of the organs). If the diagnosis of bilateral ovarian malignant tumors (high-grade plasmacytoid stage IIIC) is confirmed, prompt medical attention is recommended for diagnosis and treatment.