martedì 8 luglio 2008
Figure 1, Figure 2, Figure 3, and Figure 4: CT images of the bilateral parotid Warthin tumors.
Diagnosis: Warthin tumor
Warthin tumor (also referred to as papillary cystadenoma lymphomatosum) is the second most common benign tumor of the parotid gland with only pleomorphic adenoma being more common. Warthin tumor comprises 4%-10% of all parotid tumors. They are the most common bilateral salivary gland tumor with an estimated 5% to 14% of cases presenting with bilateral glandular involvement.
Warthin tumors are ovoid, encapsulated tumors that are either completely solid or solid with cystic components. The most common location of presentation is the parotid tissue adjacent to the angle of the mandible. Warthin tumors are believed to arise from the embryologic entrapment of heterotopic salivary gland ductal epithelial tissue within intraparotid or periparotid lymph nodes.
Patients typically present with painless swelling. The peak incidence is the fifth to seventh decade of life. Risk factors include cigarette smoking and radiation exposure. Malignant degeneration and facial nerve involvement are extremely rare. Treatment for Warthin tumors is surgical with superficial parotidectomy.
Ultrasound images demonstrate a well demarcated, hypoechoic mass or a solid mass with multiple anechoic internal areas. On CT, Warthin tumors are homogeneous, enhancing soft tissue densities that contain no calcification. If calcifications are present in a benign appearing parotid mass, the diagnosis of pleomorphic adenoma should be favored. Warthin tumors are traditionally located in the posterior aspect of the tail of the parotid gland but the tumors have been known to arise from periparotid lymph nodes. Cyst formation is common and the larger the tumor the greater the chance for cystic change. On MR imaging, the tumors have low T1 and high T2 signal (similar to pleomorphic adenomas). Warthin tumors are rich in mitochondrium and therefore will accumulate Tc-99m pertechnetate on salivary scintigraphy. Unfortunately, oncocytomas and the extremely rare oncocytic carcinoma both accumulate pertechnetate as well. Imaging findings that suggest a malignant parotid mass include; irregular margins, heterogeneous density/signal intensity, regional lymphadenopathy, adjacent soft tissue or bone invasion, and facial nerve perineural spread of tumor. Often, parotid masses will go to biopsy for a definitive diagnosis.