Giant submandibular gland tumor: mucoepidermoid carcinoma within the pleomorphic adenoma (mixed tumor).

Pleomorphic adenoma (mixed tumor) is the most common type of salivary gland tumors, most often involving the parotid glands. The study presented a case of a giant pleomorphic adenoma of the submandibular gland in a 78-year old woman. Due to the initially slow and progressive growth (during a period of 25 years) without treatment, the tumor attained a size of 25×19×16 cm and a weight of 4 kg. The patient underwent surgery. The histopathological examination showed that the tumor was subject to malignant transformation: within the pleomorphic adenoma one observed mucoepidermoid carcinoma lesions of high-degree malignancy. In spite of the good postoperative esthetic and functional effect the patient was diagnosed with distant metastases to the lungs.