Pleomorphic adenomas (benign mixed tumors) form the majority of neoplasms arising from the parotid gland. Pleomorphic adenomas should not recur after adequate surgical excision. Most recurrences can be traced to enucleation of the mass with no appreciation of the pseudopodia-like extensions of tumor. Although it appears encapsulated, if a surrounding cuff of normal tissue is not removed along with the tumor, the risk of recurrence is high.18 Recurrences frequently occur in multiple sites and are significantly more difficult to treat. Consequently, the treatment of choice for a pleomorphic adenoma of the parotid gland is excision of tumor with a surrounding cuff of normal tissue. Because 90% of pleomorphic adenomas arise lateral to the plane of the facial nerve, the treatment usually involves a complete or partial excision of the superficial lobe of the parotid gland. The extent of dissection of the facial nerve and the amount of parotid tissue resection depend on the size, location, and histology of the tumor.18 Small adenomas located in the tail of the parotid gland may only require dissection of the lower division of the facial nerve with removal of the tumor and the surrounding parotid tissue, avoiding unnecessary dissection of the upper division. Larger tumors of the superficial lobe usually require a complete superficial parotidectomy. Deep lobe tumors usually require a total parotidectomy, with facial nerve preservation. Although there is some controversy regarding the extent of resection of normal tissue surrounding a pleomorphic adenoma, there is universal agreement that capsular penetration should be avoided in order to minimize the risks of recurrence.
Recurrent pleomorphic adenomas may present a more complex problem. The scarring and altered anatomy in such cases place the facial nerve at greater risk of surgical injury during the dissection. Under such circumstances, facial nerve monitoring during revision surgery may be helpful in reducing the risk of damage to the facial nerve. Frequently there are multiple foci of recurrence, and they may continue to manifest over several years. Provided that a recurrence is nonprogressive and asymptomatic, it may be prudent to observe such stable recurrent disease for sometime. During this period of observation, other recurrences may become manifest and, in such cases, multiple surgeries can thus be avoided.18 Another reason for observing small asymptomatic recurrent pleomorphic adenomas is the increased risk to the facial nerve during revision surgery. Radiotherapy may be considered in the treatment of recurrent pleomorphic adenoma when surgery is no longer a feasible option.
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