A malignant neoplasm involving the buccal mucosa. The disease is cheek mucosa cancer (MONDO_0004645). Also known as: buccal mucosa cancer, cancer of buccal mucosa, malignant buccal mucosa neoplasm, malignant buccal mucosa tumor, malignant buccal mucosa tumour, malignant neoplasm of buccal mucosa, malignant neoplasm of cheek, inner aspect, malignant neoplasm of the buccal mucosa.