Case 10

Discussion:

Pleomorphic adenoma is the most common parotid gland tumor representing about 70-80 percent of all benign parotid tumors. More than 84 percent of pleomorphic adenomas occur in the parotid gland, 8 percent occur in the submandibular gland, and 6.4 percent occur in the minor salivary glands. 90percent of pleomorphic adenomas arise lateral to the facial nerve (superficial lobe). They are typically seen in middle aged women presenting as a painless slowly growing mass. Facial nerve function is usually not affected even with large size tumor. Typically solitary and well demarcated. They may appear heterogeneous secondary to hemorrhage, calcification, and necrosis. Malignant transformation is seen in 2-5 percent of cases. If the fibrous capsule can be completely removed, these tumors can be cured with surgery. Local recurrence can occur when portions of the capsule is left. The rate of successful cure after recurrence is less than 25 percent, and recurrence rates of up to 50 percent are reported. Facial nerve injury can occur during resection of these tumors. 3:2 female to male ratio.

CT allows direct, bilateral visualization of the salivary gland tumor and provides information about overall dimension and tissue invasion. MRI provides superior soft tissue delineation. But overall the imaging appearance is non specific; neither CT nor MRI can make a definitive diagnosis, although it has been reported that very high T2 weighted MR imaging appearance was very suggestive of pleomorphic adenoma. However, fine needle aspiration is often required for definitive diagnosis.

References:

• Cohen EG; Patel SG; Lin O; Boyle JO; Kraus DH; Singh B; Wong RJ; Shah JP; Shaha AR. Fine-needle aspiration biopsy of salivary gland lesions in a selected patient population. Arch Otolaryngol Head Neck Surg 2004 Jun;130(6):773-8.
• Koyuncu M; Sesen T; Akan H; Ismailoglu AA; Tanyeri Y; Tekat A; Unal R; Incesu L. Comparison of computed tomography and magnetic resonance imaging in the diagnosis of parotid tumors. Otolaryngol Head Neck Surg 2003:129:726-32.
• Stennert E; Guntinas-Lichius O; Klussmann JP; Arnold G. Histopathology of pleomorphic adenoma in the parotid gland: a prospective unselected series of 100 cases. Laryngoscope 2001 Dec;111(12):2195-200