Continuous optimization of diagnosis and treatment of malignant tumors has led to significantly prolonged survival in cancer patients. Despite the recent increase in the incidence of multiple primary malignant tumors (MPMT), it remains rare in clinical practice; therefore, normative guidance on its etiology, diagnosis, and treatment is insufficient. Here we describe the case of a patient with three primary malignant tumors, namely breast cancer, diffuse astrocytoma, and hepatic malignant perivascular epithelioid cell tumors (PEComa) and discuss relevant literature.