Chapter 20

Parotid Gland

R. Anthony Carabasi III

John C. Kairys

I Introduction

A Anatomy

Embryology. The parotid gland is the largest of the salivary glands. The average gland weighs 25 g. It appears in the fourth week of gestation and originates from the epithelium of the oropharynx.

Description

The gland covers the masseter muscle, extends posteriorly beyond the vertical ramus of the mandible, and abuts the external auditory meatus.

The gland is enclosed by a dense fascial sheath. The tightness of this fascia is responsible for the severe pain that accompanies acute swelling of the gland (acute parotitis).

Classically, the parotid gland was thought to have two lobes, superficial and deep. Anatomically, this is probably not the case, but it is useful to think of the gland in this way when discussing the surgical treatment of parotid disease.

Drainage of saliva is via Stensen's duct. This duct exits anteriorly, pierces the buccinator muscle, and enters the oral cavity opposite the second upper molar. The opening is marked by the parotid papilla, which may be felt by the tongue or a finger.

B Innervation of the parotid gland

(Fig. 20 -1)

The facial nerve enters the posterior part of the gland immediately after emerging from the stylomastoid foramen. This nerve divides within the substance of the gland into two parts, the zygomaticofacial and the cervicofacial, which eventually split into five major branches:

Temporal

Zygomatic

Buccal

Mandibular

Cervical

The facial nerve and its branches separate the superficial and deep portions of the gland (Fig. 20 -2).

The muscles of expression are supplied by the facial nerve on the ipsilateral side of the face.

II Benign Neoplasms

Approximately 80% of parotid tumors are benign. The most common presenting feature of these tumors is a painless mass. Many are multicentric and have a high incidence of local recurrence. Facial paralysis is rare. Very careful identification and surgical treatment, which consist of excision that includes a margin of normal gland, are required. Extension into the deep lobe requires a total parotidectomy. The facial nerve should be spared, if

possible, during surgery for benign parotid neoplasms. A discussion of the different types of benign tumors follows.

A Mixed tumors

Mixed tumors are so named because they contain both stromal and epithelial components.

Mixed tumors are the most common benign salivary tumors and account for 60% of all parotid tumors. P.394

FIGURE 20-1 Innervation of the parotid gland.

They are slow -growing tumors but may be quite large at the time of presentation.

At surgery, mixed tumors often appear to “shell out” easily; that is, they seem easy to remove from the surrounding normal tissue. However, this excision invariably leaves nests of residual tumor, resulting in a recurrent tumor that requires re-excision.

Radiation therapy has no substantial effect.

B Papillary adenocystoma (cystadenoma) lymphomatosum (Warthin's tumor)

These tumors consist of both epithelial and lymphoid elements.

They are soft (cystic) when palpated.

This interesting tumor arises from the ducts of the gland. It is the most common parotid malignancy and constitutes 9% of all parotid tumors.

Types

Low-grade tumors are the more common form and are the tumors seen most frequently during childhood.

They generally feel soft when palpated and appear encapsulated at surgery.

They are treated by excision, with preservation of those facial nerve branches that are not directly involved by the lesion.

When low -grade tumors are treated properly, the 5-year survival rate is approximately 95%.

High-grade tumors are extremely aggressive, unencapsulated tumors that invade the gland widely.

Treatment must be radical and includes total parotidectomy, including the facial nerve, plus radical neck dissection (see Chapter 19, II D 1). Neck dissection is done even without palpable nodes, because there is a high incidence of microscopic nodal metastasis.

Surgery is usually supplemented by postoperative radiation.

The 5-year survival rate is 42% with optimal treatment.

B Malignant mixed tumors

These tumors are the second most common type of malignancy and are responsible for 8% of all parotid tumors.

The treatment is total parotidectomy; a radical neck dissection is also done for either palpable adenopathy or a high-grade tumor.

C Squamous cell carcinoma

Squamous cell carcinoma is a rare tumor in the parotid gland.

It is very hard on palpation and is usually accompanied by pain and nerve paralysis.

It is important to differentiate this lesion from a metastasis arising from a primary tumor elsewhere in the head and neck.

The 5-year survival rate is approximately 20%.

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D Other lesions

Other lesions include adenocystic carcinoma (cylindroma), acinic cell adenocarcinoma , and adenocarcinoma.

Treatment is by total parotidectomy.

Neck dissection is added when obvious nodal disease for high-grade lesions is present.

High-grade, recurrent, and inoperable tumors should be treated with radiation.

E Malignant lymphoma

Malignant lymphoma may arise as a primary tumor in the gland. The treatment is the same as for other lymphomas (see Chapter 19, XI ).

IV Parotid Trauma

A Lacerations

Lacerations in the area of the parotid may damage the parenchyma of the gland, Stensen's duct, or the facial nerve.

Parenchymal damage without injury to Stensen's duct usually heals spontaneously.

Stensen's duct. If this duct is lacerated or transected, it should be repaired over a small catheter. This catheter is sutured to the oral mucosa and left in place for 10 days.

Facial nerve injuries

These nerves may recover spontaneously if only a distal branch is injured.

If a main trunk is injured, it requires meticulous repair by primary anastomosis or nerve grafting.

If the injured area is hard to expose, a superficial parotidectomy should be done to facilitate repair.

B Foreign bodies

Foreign bodies (e.g., bullets) should be removed.

V Inflammatory Disorders

A Acute suppurative parotitis

Acute suppurative parotitis is usually found in patients who are debilitated and dehydrated and who have poor oral hygiene.

The offending organism is usually Staphylococcus aureus.

It most likely enters the gland from the mouth via Stensen's duct.

The dehydrated patient whose salivary glands are not secreting actively is susceptible to rapid growth of the organism in this favorable environment.

The bacterial proliferation leads to an intense inflammatory reaction in the gland, with edema and severe pain.

Initial treatment includes hydration, antibiotics, and measures to promote salivation, such as occasionally sucking on a lemon.

Cultures are taken from Stensen's duct.

Antibiotics are initially directed against S. aureus and are later adjusted as indicated by the results of the cultures.

Surgical drainage is required if the process is not arrested by the preceding measures.

An incision is made around the angle of the mandible, and multiple horizontal incisions are made in the parotid fascia.

There are usually multiple abscesses, and each must be drained.

The wound is left open to ensure adequate drainage.

B Calculous sialadenitis

Calculous sialadenitis is a condition caused by stones in the salivary ducts. If obstruction of the duct occurs, inflammation and intermittent painful swelling of the gland follow.

Diagnosis

Radiographs may show the stones.

A sialogram, in which contrast dye is injected into the draining duct, also shows areas of obstruction and is useful in patients when the stone is not radiopaque.

Surgery

When the stone is near the end of the duct, it can be removed transorally.

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If it is deep in the gland, it can be removed by an external incision.

If multiple stones are present and pain recurs, the entire gland should be removed.

Variants. Sialadenitis can occur without stones.

If there is a stricture of the duct on the sialogram, it should be dilated.

If symptoms persist, surgery may be necessary to remove the gland.

VI Evaluation and Management of Parotid Masses

A History and physical examination

History and physical examination can often differentiate among benign, malignant, and inflammatory processes.

A slowly enlarging, distinct mass can be either a benign neoplasm or a malignant neoplasm.

A rapidly enlarging, firm distinct mass associated with firm, ipsilateral adenopathy suggests a malignancy.

A mass associated with pain or facial nerve paralysis usually indicates a malignancy.

Acute, painful swelling in one or both glands, associated with fever or systemic symptoms, indicates an inflammatory process.

Intermittent pain and swelling in the gland suggest calculus sialadenitis. A stone may occasionally be palpable on intraoral examination.

A careful head and neck examination must be performed. Metastatic disease in a parotid lymph node (drainage from the upper two thirds of the face and the anterior scalp) may present as a mass in or near the parotid gland.

B Diagnostic studies

Diagnostic studies may provide information that dictates the extent of surgery required, thus permitting better counseling of the patient preoperatively. However, some surgeons argue that no diagnostic studies are required because operation is indicated in most cases, and the extent of resection is dictated by the pathology encountered.

the following statements is true?

A Such signs and symptoms are common and should not be worked up unless they worsen.

B An MRI scan should be obtained, but gadolinium enhancement and its attendant risks are not necessary. C Brain stem evoked response audiometry is likely to be normal.

D The patient should be assumed to have an acoustic neuroma until proven otherwise. E Conditions that cause such problems do not affect the other ear.

View Answer

Questions 2–3

A 35 -year -old man has right -sided serous otitis media and a right upper neck mass.

2.It is most important to evaluate this patient for which of the following?

A Cancer of the right ear B Cancer of the right tonsil

C Cancer of the right maxillary sinus D Cancer of the nasopharynx

E Hodgkin's lymphoma View Answer

3.Which of the following will be the primary treatment for this tumor?

A Local excision to negative margins

B Wide local excision and radical neck dissection

C Neoadjuvant chemotherapy followed by resection of residual tumor

D Unilateral radiotherapy with combined chemotherapy

E Bilateral radiotherapy

View Answer

Questions 4–5

A 65 -year -old man is found to have a small invasive squamous cell carcinoma of the right vocal cord. The right vocal cord is paralyzed, and a lymph node in the right anterior neck is 4 cm in diameter.

4.The stage of the tumor is which of the following?

A T2N1 B T2N2a C T3N1 D T3N2a E T4N3

View Answer

5.Optimal treatment of the primary tumor should include which of the following?

A Total laryngectomy

B Vertical hemilaryngectomy

C Supraglottic (horizontal) laryngectomy D Right cordectomy

E Chemotherapy View Answer

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Questions 6–7

A 55 -year -old woman presents with complaint of a mass overlying the angle of the right mandible. She says the mass has been slowly enlarging over the past 2–3 years and that the mass is painless. On physical examination, it is firm and overlies the angle of the right mandible and the area between the angle and the tragus of the ear. Neurologic examination of the head and neck is completely normal.

6. Which of the following does this mass most likely represent?

A Mucoepidermoid cancer of the parotid gland B Acute parotitis

C Benign mixed tumor of the parotid gland (pleomorphic adenoma)

D Malignant mixed tumor of the parotid gland

E Hemangioma of the parotid gland

View Answer

7. What will be the optimal treatment for this lesion?

A Radiation therapy

B Total parotidectomy with preservation of the facial nerve C Total parotidectomy including resection of the facial nerve D Superficial parotidectomy

E Enucleation

View Answer

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Answers and Explanations

1. The answer is D (Chapter 18, IV F 2). These are common presenting systems of an acoustic neuroma. Evaluation for acoustic neuroma is indicated in all cases of unilateral hearing complaints, especially when hearing loss is documented. Magnetic resonance imaging (MRI) of the brain with internal auditory canal views and gadolinium contrast is sensitive in 98% of patients with acoustic neuroma. Complications associated with gadolinium are exceedingly rare, and this contrast should always be used in an MRI to look for a tumor. Brain stem auditory response testing may or may not be normal in cases such as this. The differential diagnosis with this presenting complaint is quite extensive, and it includes processes that result in bilateral hearing loss.

2–3. The answers are 2-D and 3-E (Chapter 19, IV C; Chapter 19, IV B 2, C 2 b). The two most common presenting symptoms of cancer of the nasopharynx are enlarged posterior cervical lymph nodes and unilateral serous otitis media. Cancer of the right ear, right tonsil, or right maxillary sinus or Hodgkin's lymphoma generally do not cause otitis media and usually occur in an older age group. Hodgkin's lymphoma will lead to serous otitis media only if Waldeyer's ring involvement has led to eustachian tube dysfunction, which is a rare occurrence.

Bilateral radiotherapy is the primary treatment for all epithelial nasopharyngeal tumors.

4–5. The answers are 4-D and 5-A (Chapter 19, II C 3, VIII D 3; Chapter 19, VIII E 4). Any carcinoma of the vocal cord that leads to fixation of the cord or of the hemilarynx is at least T3. Massive involvement of surrounding soft tissues will make the tumor stage T4. The presence of a single homolateral lymph node greater than 3 cm but less than 6 cm in diameter makes the stage of the neck node N2a. Multiple small lymph nodes on the same side of the neck as the primary tumor are classified N2b, and lymph nodes involving the opposite side of the neck change the staging to N3.

T3 tumors cannot be adequately treated with partial laryngectomy in most cases; total laryngectomy is required. Radiation therapy is used postoperatively as a planned combined treatment in most cases. Chemotherapy is used for inoperable cases or in experimental protocols.

6–7. The answers are 6-C and 7-D (Chapter 20, II A 1–4 ). The history given is most consistent with a benign neoplasm of the parotid gland. Benign mixed tumors are the most common benign tumors of the salivary glands. Benign salivary tumors account for 60% of all parotid tumors. Malignant tumors, such as a mucoepidermoid cancer, usually grow more rapidly and are more often associated with facial nerve paralysis. The absence of pain makes acute parotitis unlikely. Hemangiomas of the parotid gland are much rarer than benign mixed tumors.

The optimal treatment for a benign mixed tumor is removal of the tumor with a margin of normal parotid gland. This usually can be accomplished with a superficial parotidectomy. Although these tumors often appear to shell out, removal by simple enucleation results in a very high recurrence rate. Excision of the entire gland with or without the facial nerve is indicated for malignant tumors. Radiation therapy does not have a role in the management of this lesion.