65 PAROTID TUMORS
Joyesh K. Raj M.D., William R. Nelson M.D.

1. What is the differential diagnosis of a mass located in front of the ear in a patient of any age?

Show answer
If the mass is painless, discrete, nontender, and located just anterior or just beneath the ear lobe, a parotid tumor is the first choice. The differential diagnosis for other isolated masses include parotitis, primary salivary neoplasm, upper jugular chain node enlargement, tumor of the tail of the submandibular gland, enlarged preauricular or parotid lymph node, branchial cleft cyst, epithelial inclusion cyst, or any mesenchymal neoplasm. Diffuse unilateral enlargement of the parotid gland indicates parotid duct obstruction that can either be persistent or intermittent because of calculi in the main duct. Bilateral diffuse enlargement may be caused by systemic conditions such as mumps, starch-eaters disease, and fatty infiltration.

2. What is the most likely diagnosis of a mass found high in the gland in front of the tragus of the ear?

Show answer
An enlarged lymph node is the most likely diagnosis, although parotid tumors are occasionally found in this location. In older patients who exhibit solar irradiated facial skin and numerous skin keratoses or have a history of skin cancer around the upper face, metastatic skin cancer in the node must be ruled out.

3. What is the likelihood that a parotid mass is malignant?

Show answer
Sixty percent of all salivary gland tumors are benign, and 40% are variably malignant. The most common benign tumor (80%) is the mixed salivary gland tumor, or pleomorphic adenoma. Although “benign,” this mixed salivary gland tumor can recur locally and behave in a locally malignant manner.

4. List the types of benign parotid tumors and their frequency.

Show answer

* Mixed tumor (pleomorphic adenoma) is most common (80%) and, although benign, has some local malignant potential.
* Warthin’s tumor: 14%
* Benign lymphoepithelial lesion: 1%
* Oxyphil adenoma, oncocytoma, and other rare lesions: < 1% each

5. In addition to the parotid, name two other locations for salivary gland tumors. What is the frequency of malignant tumors in these locations?

Show answer

* Submandibular glands: 50% malignant
* Minor salivary glands (oral cavity): 75% malignant

6. Do mixed tumors spread systemically?

Show answer
Very rarely. There have been 43 reported cases. Typically, these rare metastatic events are found in cervical lymph nodes. The lung and brain were the most common distant sites of metastatic disease, all with classical microscopic findings of mixed tumor.

7. Describe the types of malignant tumors and list their frequency.

Show answer
In the parotid region, the presence of pain, rapid enlargement of a nodule, skin involvement, or facial nerve paralysis is highly suggestive of a malignancy.

* Mucoepidermoid carcinoma: 44% (the low-grade variety of this tumor is “almost benign”)
* Malignant mixed tumor: 17%
* Acinic cell carcinoma: 17%
* Adenocarcinoma: 10%
* Adenoid cystic carcinoma: 9%
* Epidermoid carcinoma: 7%

8. Describe the characteristic behavior of adenoid cystic carcinoma.

Show answer
It is uncommon in the parotid but does recur locally with perineural invasion. It may recur 15 years or more after treatment.

9. How should a parotid mass be evaluated and treated? Should a biopsy be performed?

Show answer
A moveable, rubbery-feeling mass should not be biopsied preoperatively. A parotid lobectomy is normally carried out with dissection of the facial nerve (cranial nerve [CN] VII), followed by frozen section of the tumor. If a tumor is found to be malignant preoperatively by needle aspiration biopsy (which is obtained secondary to nerve involvement), a complete lobectomy should be performed, keeping in mind that cancer may involve one or more nerve branches. The decision about nerve branch resection can only be determined surgically with actual evidence of neural invasion. Most authorities also advocate removal of adjacent upper neck nodes. With histologic evidence of node involvement, a modified neck dissection is indicated.

10. What is the surgical treatment of a deep lobe parotid tumor?

Show answer
These are quite uncommon because the lobe is only one fifth of the size of the entire gland and lies completely beneath the facial nerve (CN VII). Typically, a superficial parotidectomy is performed first followed by dissection and preservation of the facial nerve. Then the tumor in the deep lobe is removed along with any residual deep lobe tissue.

11. What does a partial or temporary facial nerve (CN VII) paralysis in the presence of an untreated parotid mass suggest?

Show answer
With gradual paralysis, cancer is the likely diagnosis (> 95%). Sudden onset of unilateral CN VII weakness suggests Bell’s palsy, which is typically the result of an inflammatory process and thus may be reversible. Mixed tumors rarely present with nerve paralysis. Facial nerve paralysis has an ominous prognosis. Radical surgery plus radiotherapy may help control cancer in rare cases.

12. What is the best imaging modality that can be used to identify parotid lesions?

Show answer
Deep lobe tumors occasionally extend into the oral pharynx and oral cavity, and the margins of infiltration as well as the extent of tumor are best delineated by magnetic resonance imaging (MRI). This, however, cannot differentiate between malignant and benign lesions. Routine MRI is not necessary when treating a freely moveable superficial parotid tumor.

13. Can children develop parotid tumors?

Show answer
Parotid tumors are uncommon in children, and a greater proportion of their tumors are malignant (50%).

14. What is the cause of parotid tumors?

Show answer
The cause is not clear. Inflammatory disease or stones in the parotid duct have been incriminated, and smoking may play a part in the production of Warthin’s tumors.

15. What is the recommended treatment of benign-appearing parotid tumors?

Show answer
As a rule, it is safer to remove all parotid masses. The only exceptions are long-standing parotid lesions of apparently benign type in older or infirm patients. Aspiration biopsies can be useful here to confirm the diagnosis of mixed tumors or other benign lesions in situations in which surgery would be high risk.

16. What is the most likely diagnosis of a recently enlarging parotid mass in a patient who is HIV positive?

Show answer
A benign lymphoepithelial lesion is most likely. If needle biopsy confirms this diagnosis, surgery is not necessary because of the benign nature of the process in the face of eventual AIDS development. If a cyst is present, fluid aspiration can decrease or temporarily eliminate the swelling.

17. If a malignancy is identified on a frozen section of the superficial lobe of the gland, is further surgery necessary?

Show answer
Removal of the remaining salivary tissue, including the deep lobe, is usually advocated. Low-grade mucoepidermoid carcinoma does not require radical removal. Careful histologic study, of course, is absolutely essential in determining the type of malignant neoplasm. If cancer is confirmed, a limited upper neck dissection is advised. A classical neck dissection is not performed in patients with parotid cancer unless there is evidence of nodal disease.

18. Is further surgery necessary when a mixed tumor is identified in the superficial lobe?

Show answer
Few, if any, cases recur if the resection margins are grossly clean, there is no spillage at surgery, and there is no microscopic penetration of the capsule.

19. When is the appropriate time for nerve grafting after parotid cancer resection?

Show answer
Interposition grafting can be performed after noncancerous frozen sections of the nerve ends have been confirmed. A nerve graft from the contralateral greater auricular nerve is usually preferred.

20. Is it necessary to dissect the facial nerve (CN VII) when performing a parotid tumor resection?

Show answer
Yes. For a Warthin’s tumor, which usually develops in the lower part of the parotid, careful local excision (without identifying the nerve) is permissable because local recurrence is uncommon. Mixed tumors arising in rare anterior locations may also be excised locally without nerve dissection.

KEY POINTS: PAROTID TUMORS

1. The most common benign tumor is a mixed tumor or pleomorphic adenoma.
2. The most common malignant tumor is mucoepidermoid carcinoma.
3. The facial nerve branch most commonly injured during a parotidectomy is the ramus marginalis mandibularis.

21. Which facial nerve branch is most commonly injured during a parotidectomy?

Show answer
Most commonly injured is the ramus marginalis mandibularis, the lowest branch of the nerve that innervates the depressor muscles of the lower lip. This nerve must be preserved. If weakness of the lower lip does occur because of neuropraxia (a common complication even of careful surgery), it will with resolve within 8 weeks.

22. What are the most common causes of postparotidectomy facial nerve paresis?

Show answer
Postoperative palsy is rare. Neuropraxia is typically caused by rough handling of the facial nerve and branches. Coagulation of bleeding vessels, which leads to temporary thermal injury of the nerve; careless suctioning around the nerve itself; and excessive traction of the nerve may result in several weeks of distressing palsy. Despite the greatest care, some patients may still develop temporary paralysis, but most should resolve in weeks.

23. Why do some patients complain of anesthesia of the ear lobe after surgery?

Show answer
They have temporary or permanent injury to the posterior branch of the greater auricular nerve. This nerve can be preserved if it is not involved with tumor and not adherent to the tumor itself.

24. When is a lymph node dissection indicated?

Show answer
Only for clinically positive (palpable) nodes and high-grade cancers.

25. When should postoperative radiation therapy be used after parotidectomy?

Show answer
In all except very low-grade cancers. A radical neck dissection is not performed without evidence of nodal involvement.

26. What are the cure rates with surgery for parotid cancer?

Show answer
In low-grade cancers, cure rates may approach 90%. In one large series of all types of cancers, survival rates at 5, 10, and 15 years were approximately 62%, 54%, and 47%, respectively.

27. Is the stage or histologic grade of the tumor more important in determining the prognosis of adenoid cystic carcinoma?

Show answer
Multivariate analysis shows that tumor stage is more prognostic than tumor grade. Early-stage tumors, even in the face of high-grade histology, enjoy a good prognosis.

28. How common is a salivary fistula after superficial parotidectomy?

Show answer
Rare. If all except a few fragments of the superficial lobe are removed cleanly, fistulas should not occur. The deep lobe itself is rarely, if ever, the source of salivary leak after removal of the superficial lobe.

29. What is Frey’s syndrome?

Show answer
Gustatory sweating, also known as auriculotemporal nerve syndrome, is a well-known sequela after parotidectomy. Patients become socially debilitated by episodes of unilateral hyperhidrosis, pain, and flushing in the cutaneous distribution of the auriculotemporal nerve when they eat. The most widely accepted theory of the pathophysiology is the aberrant regeneration theory. In this theory, autonomic fibers from the parotid gland, when damaged by surgery or trauma, regrow into the sheath of the severed auriculotemporal nerve, causing the syndrome. Nonsurgical treatment includes medications such as topical anticholinergics and systemic atropine. Surgical treatments include neurectomy with or without the insertion of a graft to provide a barrier to reinnervation.

30. When is chemotherapy used after parotidectomy in the face of malignancy?

Show answer
Total gross excision of parotid cancer, sparing facial nerve if possible and followed by regional radiotherapy, provides excellent rates of control and survival with only moderate toxicity. Patients presenting postoperatively with gross residual tumor or recurrence after surgery should be considered for trials of more aggressive treatment with combined chemotherapy or altered fractionation schemes of irradiation.

31. Can a mixed tumor metamorphose into a true malignancy?

Show answer
Possibly, but it is rare.

32. Can facial nerve (CN VII) function be preserved despite the sacrifice of facial branches?

Show answer
Occasionally, lip elevator function can be maintained by preserved branches from the zygomatic or buccal branches of the facial nerve that cross over and accomplish similar function as the cut nerve branch.

33. Which tumor suppressor gene is most often associated with parotid cancer?

Show answer
p53 has been found in some parotid cancers. These lesions are usually advanced and larger than those without p53.

References
WEB SITE
http://www.acssurgery.com
BIBLIOGRAPHY
1. Blevins NH, Jackler RK, Kaplan MJ, Boles R: Facial paralysis due to benign parotid tumors. Arch Otol Head Neck Surg 118:427-430, 1992.
2. Christensen NR, Jacobsen SD: Parotidectomy: Preserving the posterior branch of the great auricular nerve. J Laryngol Otol 111:556-559, 1997. Medline Similar articles
3. Goldwyn RM, Cohen MN: The Unfavorable Result in Plastic Surgery. Philadelphia, Lippincott Williams & Wilkins, 2001.
4. Ismail Y, McLean NR, Chippindale AJ: MRI and malignant melanoma of the parotid gland. Br J Plast Surg 54:636-637, 2001. Medline Similar articles <a href=”http://dx.doi.org/10.1054/bjps.2001.3674″>Full article
5. Kelley DJ, Spiro RH: Management of the neck in parotid carcinoma. Am J Surg 172:695-697, 1996. Medline Similar articles Full article
6. Malata CM, Camilleri IG, McLean NR, et al: Malignant tumors of the parotid gland: A 12-year review. Br J Plast Surg 50:600-608, 1997. Full article
7. Ogata H, Ebihara S, Mukai K: Salivary gland neoplasms in children. Jpn J Clin Oncol 24:88-93, 1994. Medline Similar articles
8. Spiro RH, Huvos AG: Stage means more than grade in adenoid cystic carcinoma. Am J Surg 164:623-638, 1992. Medline Similar articles
9. Teymoortash A, Werner JA: Value of neck dissection in patients with cancer of the parotid gland and a clinical NO neck. Onkologie 25:122-126, 2002. Medline Similar articles Full article
10. Toonkel LM, Guha S, Foster P, Dembow V: Radiotherapy for parotid cancer. Ann Surg Oncol 1:468-472, 1994. Medline Similar articles
11. Tullio A, Marchetti C, Sesenna E, et al: Treatment of carcinoma of the parotid gland: The result of a multicenter study. J Oral Maxillofac Surg 59:263-270, 2001. Medline Similar articles Full article
12. Yugueros P, Loellner JR, Petty PM: Treating recurrence of benign parotid pleomorphic adenomas. Ann Plast Surg 40:573-576, 1998.