A primary or metastatic malignant neoplasm involving the oral cavity. The majority are squamous cell carcinomas. The disease is oral cavity cancer (Monarch Disease Ontology id MONDO_0005515). Also known as: cancer of oral cavity, malignant mouth neoplasm, malignant mouth tumor, malignant mouth tumour, malignant neoplasm of mouth, malignant neoplasm of oral cavity, malignant neoplasm of the mouth, malignant oral cavity neoplasm.