Chapter 28. Neck Neoplasms & Neck Dissection

Essentials of Diagnosis

• Primary neoplasms of the soft tissue in the head and neck are rare.
• The most common benign tumors are paragangliomas and nerve cell tumors.
• The most common malignant neoplasm is metastatic squamous cell carcinoma from the upper aerodigestive tract.
• The evaluation of a metastatic squamous cell carcinoma without an easily identifiable primary site is extensive and treatment is controversial.
• Neck dissections are performed to treat metastatic neoplasms and to determine the presence of occult metastasis.

General Considerations

Neck neoplasms include not only metastatic squamous cell carcinoma but also a number of other primary neck tumors. Metastatic squamous cell carcinoma arises from the upper aerodigestive tract and is present in the lymph nodes and in the neck; other primary tumors arise from the soft tissue in the neck, such as fat, fibrous tissue, muscle, blood vessels, lymphatic vessels, nerves, and paraganglia (Table 28–1). These primary tumors are fairly uncommon, often making a pathologic diagnosis difficult. The evaluation of all neck masses consists of obtaining a complete history and conducting a physical exam.

Clinical Findings

Symptoms and Signs

The presenting symptom of a neck neoplasm is a painless enlarging neck mass that may grow extremely slowly or very rapidly. On physical examination, there is often a well-circumscribed mass in the neck. The location of the mass sometimes suggests its cause.

Imaging Studies

Imaging with computed tomography (CT) or magnetic resonance imaging (MRI) is critical for these lesions, especially if these studies are performed before a biopsy is obtained. A preoperative study can better assess both the size and the extent of the lesion without confounding factors such as bleeding and edema. An MRI is often the study of choice because it allows a greater differentiation of soft tissue. A positron emission tomography (PET) scan in evaluating patients with metastatic disease can identify additional tumor masses. Additional studies such as angiography and, recently, magnetic resonance angiography (MRA) add valuable information to the diagnosis of vascular lesions (eg, carotid body tumors and vascular malformations).

Special Tests

Fine-Needle Aspiration (FNA) Biopsy

A tissue specimen is vital for the diagnosis of neck neoplasms and can be obtained via a fine-needle aspiration biopsy (FNAB). Metastatic squamous cell carcinoma has an excellent specificity and sensitivity for FNAB. Additional studies such as flow studies, immunohistochemistry techniques, or electron microscopy may be required for an accurate diagnosis of these specimens.

Open Biopsy

Open biopsies consist of incisional and excisional biopsies. A small superficial lesion or any lesion smaller than 3 cm should undergo an excisional biopsy with sufficient normal surrounding tissue for adequate, clear margins. An incisional biopsy should only be entertained if the mass is larger than 3 cm. If metastatic squamous cell carcinoma is suspected, an open biopsy should not be considered unless all other avenues have been exhausted and at least two inconclusive FNAB.

Other Tests

After either an FNAB or open biopsy is performed, the specimen then undergoes evaluation with light microscopy. Immunohistochemistry techniques can stain for cytokeratin, leukocyte common antigen, S-100, and myoglobin to differentiate sarcomas, melanomas, and epithelial carcinomas. Electron microscopy is used to aid in the diagnosis in patients where light microscopy and immunohistochemistry techniques prove ineffective.

Benign Neoplasms

The most common benign masses in the neck are inflammatory lymph nodes and masses of salivary and thyroid gland origins. True soft-tissue benign tumors in the neck are relatively uncommon.

Paragangliomas

Paragangliomas arise from paraganglia, islands of cells derived from neural crest cells, associated with arteries and cranial nerves located at the carotid body, vagal body, along laryngeal nerves, and in the jugulotympanic region. The tumors derived from these regions are carotid body tumors, intravagal paragangliomas, and glomus tympanicum and glomus jugulare. While paraganglia cells are capable of producing catecholamines, the incidence of catecholamine-producing head and neck paragangliomas is exceedingly rare.

Carotid Body Tumors

Carotid body tumors are the most common head and neck paragangliomas. The carotid body is found at the bifurcation of the common carotid artery and responds to changes in arterial pH, oxygen, and carbon dioxide.

Clinical Findings

Symptoms and Signs

Symptoms are present only with large tumors and include pressure, dysphagia, cough, and hoarseness. On examination, the mass is palpated at the anterior border of the sternocleidomastoid muscle. It is typically mobile laterally but not vertically.

Laboratory Findings

The diagnosis requires a high index of suspicion as the location is similar to that of many other masses (eg, branchial cleft cysts and enlarged lymph nodes). Fine-needle aspiration of these lesions often yields only blood; however, if cells are obtained, FNA can offer a definitive diagnosis.

Imaging Studies

The angiogram in Figure 28–1 shows the typical findings of a splayed bifurcation of the carotid artery with a vascular blush. An MRI often proves useful in identifying other paragangliomas as synchronous and metachronous lesions occur in 25–48% of cases. Familial paragangliomas occur in 7–9% of cases.

Treatment

Surgical Measures

The treatment of these lesions is predominantly surgical. Preoperative embolization is useful to minimize blood loss in order to allow for a cleaner dissection. Surgical excision requires the following measures: (1) identification of the proximal and distal carotid artery and (2) identification and preservation of the vagus, hypoglossal, and spinal accessory nerves. Patients with large or recurrent tumors often require vascular reconstruction, which should be planned preoperatively.

Radiation Therapy

Radiation therapy is not the primary mode of therapy but has been used as the sole method of treatment in some cases such as elderly patients who are poor surgical candidates. In patients with carotid body and vagale tumors, radiation therapy alone has been shown to provide a local control rate of as much as 96%. Control rates with surgery alone range from 88% to 100%. Treatment decisions are based on surgical risks and complications; therefore, small tumors should usually be treated surgically, with radiation therapy reserved for large tumors.

Intravagal Paragangliomas

Intravagal paragangliomas typically occur in association with one of the vagal ganglia, most commonly the ganglion nodosum. Intravagal paragangliomas account for approximately 3% of all head and neck paragangliomas. Symptoms can include hoarseness, dysphagia, aspiration, tongue weakness, and Horner syndrome. Angiographic imaging shows a mass located above the carotid bifurcation, with lateral and medial displacement of the external and internal carotid arteries. FNA has been useful in the diagnosis of these tumors.

The treatment involves surgical resection, with radiation therapy reserved for patients with high surgical risk, incomplete resection, recurrent disease, and bilateral tumors. Most intravagal paragangliomas can be resected via a cervical approach. If there is intracranial extension, a middle or posterior fossa approach may be needed.

Peripheral Nerve Cell Tumors

Tumors arising from peripheral nerves typically arise from the Schwann cells in the nerve sheath. Of the many names used to describe these tumors, two in particular—schwannomas and neurofibromas—have significant clinical differences that warrant discussion. As a group, neurogenous tumors occur most commonly in the head and neck regions. They are often asymptomatic and present as lateral neck masses.

Schwannomas

Peripheral nerve schwannomas, more appropriately termed neurilemomas, are solitary, well-encapsulated tumors. Histologically, these tumors have characteristic Antoni A and Antoni B tissues. Antoni A tissue consists of palisading nuclei around central cytoplasm and Antoni B tissue is comprised of a loose edematous matrix. These tumors can arise from cranial nerves, peripheral motor and sensory nerves, and the sympathetic chain. They can sometimes present with a displaced tonsil or a lateral pharyngeal wall when the mass is located in the parapharyngeal space.

Neurofibromas

Neurofibromas differ from neurilemomas in that they are not encapsulated. The nerves in neurofibromas tend to traverse the tumors and are integral to them. While solitary neurofibromas are very rare, multiple neurofibromas are common especially in patients with von Recklinghausen disease. von Recklinghausen disease is an autosomal dominant disease with clinical findings of cafè-au-lait spots and neurofibromas.

The treatment of both neurilemomas and neurofibromas consists of simple surgical resection. The function of the affected nerve can typically be preserved with neurilemomas unless the neoplasms are intimately involved with some cranial nerves. These tumors rarely recur and malignant transformation is exceedingly rare.

Lipomas

Lipomas are the most common benign soft-tissue neoplasms. They arise from the subcutaneous tissue and present as painless, smooth, encapsulated, and round masses. Fifteen to twenty percent of all lipomas occur in the head and neck. Most of these neoplasms are solitary lesions and are easily treated with excision. Recurrences are very rare.

Malignant Neoplasms

The most common malignant neoplasm in the neck is a cervical metastasis from a primary tumor in the upper aerodigestive tract. In most cases, when a lymph node metastasis in the neck is identified, the primary tumor also can be identified and the treatment proceeds according to the principles dictated by the stage of the primary disease. In less than 10% of cases, the primary site is not located and further evaluation is required. Malignant neoplasms of the salivary, thyroid, and parathyroid glands also can present as malignant cervical masses or with metastases to cervical lymph nodes. (See the following chapters for information on these neoplasms: Chapter 17, Malignant Diseases of the Salivary Glands; Chapter 41, Malignant Thyroid Disorders; and Chapter 42, Parathyroid Disorders.) Other common primary malignant neoplasms of the head and neck are lymphomas. Rarely are sarcomas seen in the head and neck.

Unknown Primary Squamous Cell Carcinoma

Clinical Findings

Symptoms and Signs

A common problem with an unknown primary squamous cell carcinoma is determining the site of the primary tumor when a known metastatic node has been identified. The incidence of an unknown primary tumor is between 2% and 8% of all patients with head and neck squamous cell carcinoma. The patient examination shows a mass in the neck with no masses or abnormalities in the upper aerodigestive tract. It is often on an FNAB that the diagnosis of squamous cell carcinoma is made.

Imaging Studies

Positron Emission Tomography (PET)

The PET scan with a combination of CT scan is now preferred over an MRI as an initial imaging modality. It shows increased glycolytic activity of tumor cells identifying a potential tumor site. PET scans can identify small tumors, typically in the base of the tongue and in the tonsil, which would have otherwise escaped detection. PET/CT combination scans have been used to follow patients after treatment to evaluate for recurrence.

MRI

If better imaging is required for a therapeutic intervention, such as surgical planning, an MRI can be advantageous as it allows for better soft-tissue distinction (Figure 28–2).

Diagnostic Tests

All patients with unknown primary tumors should undergo an exhaustive search for the primary site so that (1) site-specific treatment can be employed; (2) the area can be closely monitored for recurrence; and (3) treatment morbidity, especially with radiotherapy, is markedly reduced.

The next step in the site search is a direct laryngoscopy with biopsy, esophagoscopy, bronchoscopy, and tonsillectomy. If studies suggest a primary site that can be confirmed on direct laryngoscopy, a directed biopsy is often sufficient for the diagnosis. It is more likely that no abnormalities are noted and blind biopsies are obtained. The typical sites harboring a primary cancer are in the nasopharynx, the palatine tonsil, the base of tongue, and the pyriform sinus. The mucosa can be easily biopsied from the nasopharynx, the base of tongue, and the pyriform sinus. A tonsillectomy should be performed rather than just a biopsy as 18–26% of patients can harbor a primary tumor in the tonsil.

Staging

The staging of neck tumors is based upon the system created by the American Joint Committee on Cancer. This system takes into account the number and size of lymph nodes in the neck; a portion of this staging system is shown in Table 28–2.

Treatment

The treatment of patients with an unknown primary tumor has been controversial. While the necessity of treating the neck is undisputed, the order of surgery and radiation therapy is debated, as is the extent of the surgery needed. Some clinicians advocate primary radiotherapy with surgery to follow, while others promote primary neck dissection with postoperative radiation therapy. The advantage of primary radiotherapy is that all potential tumor sites can be treated and the neck mass may decrease in size to facilitate or in some cases avoid the neck dissection. The advantage of primary surgery is that a lower total dose of radiation may be given to the neck to prevent some complications of radiation therapy.

The need to treat all potential primary sites also is debated. Wide-field radiation therapy to encompass all potential mucosal sites carries significant morbidity, though intensity-modulated radiotherapy (IMRT) does reduce the toxicity to vital structures such as the parotid glands, optic nerve, and spinal column. Proponents of this treatment maintain that wide-field radiation therapy decreases the risk of future tumor emergence. The emergence rates of primary tumors are estimated to be 3–8% a year in patients with primary sites treated with radiation, compared to a 32–44% in patients who do not undergo this treatment modality.

The complications of radiation treatment can be severe and include xerostomia, mucositis, and persistent dysphagia. For large, unresectable tumors, palliation is an option.

General Considerations

A neck dissection is a systematic removal of lymph nodes in the neck. It serves to eradicate cancer of the cervical lymph nodes and can help determine the need for additional therapy when no lymph nodes are clinically identified. The indications for a neck dissection in the setting of no clinically palpable nodes are based on the propensity of metastasis from the primary site and the size of the primary tumor.

Classification of Neck Zones

The evaluation of the drainage pattern from the primary tumor sites in the upper aerodigestive tract has led to the understanding and identification of nodal groups at risk for cervical metastasis. The neck has been divided into six such groups called zones (Figure 28–3).

Zone I: The Submandibular and Submental Triangles

Zone I consists of the submandibular triangle and the submental triangle. The submandibular triangle is bordered by the mandible superiorly, the posterior belly of the digastric muscle posteroinferiorly, and the anterior belly of the digastric muscle anteroinferiorly. The submental triangle is the region between the bilateral anterior bellies of the digastric muscle and the hyoid bone.

Zone II: The Upper Jugular Region

Zone II is known as the upper jugular region. Its boundaries are (1) the skull base superiorly, (2) the carotid bifurcation inferiorly, (3) the posterior border of the sternocleidomastoid muscle laterally, and (4) the lateral border of the sternohyoid and stylohyoid muscles medially. The tissue encompassed within these boundaries includes the upper portion of the internal jugular vein and the spinal accessory nerve. A subsection of Zone II, the submuscular triangle, includes the most superior aspect of this zone and lies laterally to the spinal accessory nerve at the skull base.

Zone III: The Middle Jugular Region

Zone III is the middle jugular region. It is bordered by (1) the carotid bifurcation superiorly, (2) the junction of the omohyoid muscle and the internal jugular vein inferiorly, (3) the posterior border of the sternocleidomastoid laterally, and (4) the lateral border of the sternohyoid muscle medially.

Zone IV: The Lower Jugular Region

Zone IV is the lower jugular region and extends from the omohyoid superiorly to the clavicle inferiorly; it also extends to the posterior border of the sternocleidomastoid muscle laterally and the lateral border of the sternohyoid muscle medially.

Zone V: The Posterior Triangle

Zone V is the posterior triangle and includes all of the lymph nodes between the posterior border of the sternocleidomastoid medially and the anterior border of the trapezius muscle laterally; it extends to the clavicle inferiorly. This triangle encompasses the course of the spinal accessory nerve. The supraclavicular region is part of Zone V.

Zone VI: The Anterior Compartment

Zone VI is the anterior compartment and includes midline lymph nodes. The borders of this region are the hyoid bone superiorly, the suprasternal notch inferiorly, and the carotid sheaths laterally. This region is typically only dissected in conjunction with laryngectomy and thyroidectomy.

Treatment

The current classification of neck dissections includes radical neck dissection, modified radical neck dissection, selective neck dissection, and extended radical neck dissection.

Radical Neck Dissection

Radical neck dissection is defined as an en bloc removal of all nodal groups between the mandible and the clavicle; this removal includes the sternocleidomastoid muscle, the internal jugular vein, and the spinal accessory nerve inclusive of Zones I–V. Since this dissection was first classified, many modifications have been proposed, especially in staging neck dissections when no palpable nodes are present (Figure 28–4).

Modified Radical Neck Dissection

A modified radical neck dissection involves sparing at least of one of these three structures—the sternocleidomastoid muscle, the internal jugular vein, or the spinal accessory nerve—while still dissecting Zones I–V. The indications for a modified radical neck dissection include definitive treatment of the neck in the presence of metastatic disease. Since the spinal accessory nerve is rarely directly involved with disease, it tends to be preserved to decrease the pain associated with shoulder dysfunction. On occasion, all three structures can be preserved if they are not directly involved with pathologic nodes.

Selective Neck Dissection

A selective neck dissection involves the preservation of one or more zones that are typically removed in a radical neck dissection. This procedure is performed when both the treatment of the primary lesion is surgical and the risk of occult metastasis to the cervical lymph nodes is greater than 20%.

Supraomohyoid Neck Dissection

A supraomohyoid neck dissection involves Zones I–III and is usually performed in conjunction with oral cavity tumors and N0 neck disease (Figure 28–5; also refer to Table 28–2). Its most common role is in the dissection of the contralateral neck at high risk for cervical metastasis in order to avoid postoperative radiation therapy.

Lateral Compartment Neck Dissection

A lateral compartment dissection includes Zones II–IV (Figure 28–6); it is used in conjunction with the surgical resection of tumors of the larynx, hypopharynx, and pharynx. When lateral compartment dissections are needed, they are usually performed bilaterally as the lesions are fairly midline.

Posterolateral Neck Dissection

Posterolateral neck dissections include Zones II–V and include nodes in the retroauricular and suboccipital regions (Figure 28–7). These dissections are often performed when cutaneous malignant tumors metastasize to the neck.

Anterior Compartment Neck Dissection

The anterior compartment neck dissection includes Zone VI and is used for tumors found in the larynx, hypopharynx, subglottis, cervical esophagus, and thyroid. It includes the removal of the thyroid lobe and necessitates both the identification and the preservation of the parathyroid glands, with reimplantation as needed.

Extended Radical Neck Dissection

Extended neck dissections involve the additional removal of muscle, nerves, vessels, and lymph node groups as dictated by the primary disease and the presence of metastasis. Patients with disease extensive enough to warrant the consideration of a carotid resection should be evaluated preoperatively for carotid reconstruction.

Complications

The complications associated with neck dissections can occur either intraoperatively due to poor technique or postoperatively due to poor nutritional status, alcoholism, and underlying medical conditions such as diabetes.

Intraoperative Complications

Surgical complications usually stem from injury to the nerves present in the field. The mandibular branch of the facial nerve can be injured in a submandibular dissection, as can the lingual and the hypoglossal nerves. Injury to the vagus nerve is uncommon but it can lead to vocal cord paralysis, a decreased sensation of the hemipharynx, and dysphagia with a risk of aspiration. Dissection in the neck, below the deep layer of the deep cervical fascia, can cause inadvertent injury to the phrenic nerve that becomes symptomatic only in patients with significant pulmonary disease.

Postoperative Complications

Hematomas

A hematoma is a common postoperative complication. The immediate evacuation of a hematoma either by milking the drains (if small) or by exploration is necessary to both prevent wound infections and protect skin flaps.

Wound Infections

The incidence of wound infections in neck dissections without concomitant pharyngeal surgery and with the use of perioperative antibiotics is 2–5% but increases when performed in conjunction with pharyngeal or laryngeal surgery. The use of perioperative antibiotics in the latter group has decreased the incidence of wound infections as well.

Chylous Fistulas

A relatively uncommon complication is a chylous fistula; it occurs due to injury to the thoracic duct. Even with meticulous surgical technique, the incidence of a chylous leak is between 1% and 2%. This leak often becomes evident after the resumption of enteral feeds. The drain output tends to increase and is of a milky quality. The initial management includes pressure dressings and placing the patient on a medium-chain fatty acid diet. Most leaks resolve with this conservative therapy. However, if the drainage persists, is >600 cc/d, or is noted immediately postoperatively, surgical exploration with ligation of the stump may be necessary.

Carotid Artery Exposure and Rupture

The most feared complication after neck surgery is carotid artery exposure with carotid rupture. Improved surgical techniques and the use of a pedicled and free musculocutaneous flap have minimized this risk. However, patient factors such as preoperative radiation therapy, poor nutritional status, infection, and diabetes continue to be risk factors. Should the carotid artery be exposed and a sentinel bleed occur, it is advisable to electively ligate the carotid artery both proximal and distal to the rupture. The carotid artery can sometimes be managed with embolization by highly experienced neurointerventional radiologists.