A case report of carcinoma ex pleomorphic adenoma of the parotid gland that the malignant lesion was detected by advanced MRI techniques

Abstract

We present a patient with a malignant lesion diagnosed as carcinoma ex pleomorphic adenoma of the parotid gland detected by advanced MRI techniques such as diffusion-weighted MR imaging （DWI） and apparent diffusion coefficient （ADC）. A 64-year-old male was referred to our hospital due to a gradual growing left parotid tumor originally discovered 20 years earlier. MRI imaging detected a left parotid tumor 4 cm in the longer axis and 3 cm in the shorter axis. On two occasions, fine needle aspiration cytology and an echo-guided core needle biopsy indicated the possibility of a carcinoma. Total parotidectomy with facial nerve reconstruction was performed. Histological findings confirmed the presence of a carcinoma as well as hyaline degeneration. The tumor was finally diagnosed as a carcinoma ex pleomorphic adenoma by histological examination and gradual growth of the tumor. Advanced MRI techniques revealed low ADC and high DWI only in the regions of the carcinoma.