47.1
Parotid Gland
A complete surgical resection with negative margins is the primary goal when treating malignant tumors of the parotid gland. Preparation for surgery includes clinical evaluation of the patient, physical examination, including testing facial nerve function, cytologic evaluation for diagnosis, and detailed radiologic imaging evaluation for extent of disease. Imaging evaluation of parotid tumors is important, not only to document the extent of disease and establish a baseline for future comparisons, but some imaging modalities have also been shown to differentiate malignant from benign parotid tumors. The surgical approach is chosen according to the size and histologic grade of the primary tumor. If the tumor is small, low-grade, and confined to the superficial lobe of the parotid gland, a partial parotidectomy is the treatment of choice (see Chapter 35 ). Larger high-grade tumors might require more extensive resection, including sacrifice of the facial nerve, with or without neck dissection. Some advanced tumors may require resection of adjacent structures such as the auditory canal, the ascending ramus of the mandible, and temporal bone; details of these techniques are outside the scope of this chapter and are available elsewhere. Patients whose tumors are more advanced and in the deep lobe of the parotid are at greater risk of having long-term complications and they should be counseled preoperatively.
Radical Parotidectomy With Facial Nerve Resection
If clinically obvious facial nerve deficit from tumor involvement is present, sacrifice of the nerve or the branches that are involved is indicated. However, if the nerve is functioning, the decision to sacrifice it is made intraoperatively. The nerve is not amenable to salvage if it is encased by the tumor, because splitting even benign tumors that encase the nerve will result in local recurrence. However, resecting a functioning nerve for the sole purpose of achieving a “wide” margin is not recommended when the tumor does not involve the nerve. Although the decision to sacrifice the nerve or its branches is intraoperative, the surgeon must discuss this possibility and its consequences with the patient and the surgical consent should cover this possibility.
The skin incision is performed as described in superficial parotidectomy (see Chapter 35 ). If the skin is invaded by the tumor, the incision should be planned to incorporate an overlying skin island that will be resected accordingly. In cases of locally recurrent tumor, the surgical access should be through the previous parotidectomy incision and the scar should be excised. When elevating the skin flaps, the great auricular nerve (GAN) should be identified and preserved whenever possible. This can be very difficult in patients who had a previous parotidectomy. A segment of this nerve can be used as a graft to reconstruct the resected segment of the facial nerve. The facial nerve should also be identified and the segments and branches that are not involved by the tumor should be preserved. Fig. 47.1.1 shows a mucoepidermoid carcinoma (MEC) with gross invasion of the upper division of the facial nerve. Fig. 47.1.2 illustrates a recurrent parotid tumor encasing the lower division of the facial nerve. After the resection of the tumor and sacrifice of the involved branches of the facial nerve, the margins of the stumps are examined by frozen section to evaluate tumor involvement ( Figs. 47.1.3 , 47.1.4 ). Even when the nerve margin is “negative” in histologic evaluation, there can be further perineural spread, especially in adenoid cystic carcinoma (ACC), which is well known to have skip areas of normal nerve. Fig. 47.1.5 shows reconstruction of the upper division of the facial nerve using GAN graft (see Chapter 50 ). After the resection and nerve grafting, hemostasis and incision closure are done after the drain has been placed.
Mandibulotomy for Resection of Tumors of the Deep Parotid Lobe
Transcervical resection, described in detail in Chapter 35 , is feasible for most tumors of the deep lobe of the parotid gland. Some malignant tumors though, especially locally recurrent or tumors that were previously violated by an attempted transoral biopsy, benefit from an exposure that provides direct visualization of the parapharyngeal space. A more comprehensive exposure of the parapharyngeal space can be achieved with the mandibulotomy approach. This surgical technique has been well described in the literature for oropharyngeal tumors.
The preferred osteotomy to assess parapharyngeal tumors is the paramedian mandibulotomy. This position is preferred because it allows wide exposure with the following advantages:
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It preserves the sensation of the chin, lower lip, and teeth (there is no need of division of mental or inferior alveolar nerves)
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It does not require dental extraction
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It only requires division of the mylohyoid muscle (there is minimal interference with mastication or swallowing)
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It is anterior in the oral cavity, which makes the postoperative care easier and keeps the osteotomy and the hardware that is used to fix it out of the way of radiotherapy portals, if adjuvant treatment is needed.
The patient is kept with nasogastric tube feeding for a week and after this period, a trial with pureed food is made. If the trial is successful, the patient’s food intake is advanced gradually to a soft diet. Once the patient’s oral intake suffices the daily nutritional requirement, the nasogastric tube can be removed. Oral hygiene is essential for healing and to avoid infection at the osteotomy site.
Postoperative care for all cases of advanced malignant tumors in the parotid gland should include a multidisciplinary team to evaluate and help in rehabilitating the patient’s speech, swallowing, facial motricity, and lymphatic drainage for the face and neck.
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If the tumor is small, low-grade, and confined to the superficial lobe of the parotid gland, a partial parotidectomy is the treatment of choice.
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Resecting a functioning nerve for the sole purpose of achieving a “wide” margin is not recommended.
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The preferred osteotomy to assess parapharyngeal tumors is the paramedian mandibulotomy.
47.2
Submandibular Gland
Introduction
An estimated 25–50% of submandibular gland tumors are malignant, with a wide range of histologies and biologic activity. ACC, the most common primary malignancy of the submandibular gland, has a predilection for perineural spread and late distant metastases. Other common malignant histologies may also demonstrate invasive locoregional disease and have an increased risk of metastases.
Surgical management remains the standard of care for submandibular gland malignancies. In patients with initial gland enucleation who subsequently underwent definitive surgical resection, over 60% were found to have residual carcinoma. Although all submandibular masses harbor the potential for malignancy, fine needle aspiration (FNA) in some cases will suggest malignancy and therefore indicate an oncologic approach. Optimal management of submandibular gland malignancy, therefore, requires adequate preparation for appropriate tumor exposure, full resection of the gland in continuity with surrounding lymphatics and involved structures, along with the ability to perform any required reconstructive procedures when necessary.
Surgical Approach
See also Chapters 11 and 35.2 .
Incision Design and Exposure
The incision is placed at least 3 cm below the inferior border of the mandible ( Fig. 47.2.1A ). The incision extends from the submental region to the sternocleidomastoid and must be of sufficient length to achieve both appropriate tumor exposure and the ability to address the lateral cervical lymphatics when necessary ( Fig. 47.2.1B ). This often requires extension of the incision toward the mastoid with associated sacrifice of the external jugular vein and GAN. The dissection is first taken to the subplatysmal plane and a superior subplatysmal flap is elevated to the mandible. This exposure provides the maximal ability to control and elevate marginal mandibular branch of the facial nerve. The cervical motor branch to the platysma will require sacrifice. In this fashion, the level I lymphatics are mobilized off the inferior border of the mandible and the facial vessels are ligated and divided at the mandibular notch ( Fig. 47.2.2A,B ). Mobilization of these ligated superior vessels serves to elevate the marginal mandibular nerves branches providing further protection. The anterior and posterior bellies of the digastric muscle are exposed and the common facial vein is ligated ( Fig. 47.2.2C ).
Tumor Resection
Tumor resection for malignant disease should encompass a full submandibular gland resection in continuity with the level I lymphatics. Level Ia is rolled off the contralateral anterior digastric belly and rolled medially toward the mylohyoid and ipsilateral anterior digastric belly. Care is taken to include the lymph nodes situated between the two digastric bellies at their apex, as well as just superior and under the attachment of the muscle at the mandible. The nodal tissue at the superolateral junction of the anterior belly of digastric and mylohyoid is mobilized off the mandible and underlying muscles. The submental artery and vein are encountered in this region and should be ligated. This dissection proceeds inferiorly until the mylohyoid is fully exposed. Care is taken during this aspect of the dissection to assess for potential tumor adherence or involvement of the mylohyoid or digastric muscles. If noted, partial or complete muscle resection is included in the specimen.
The mylohyoid muscle is then retracted anteriorly and superiorly with a narrow Richardson retractor, which allows visualization of the lingual nerve with its attachment to the gland at the submandibular ganglion ( Fig. 47.2.3 ). The gland is then elevated and the hypoglossal nerve is identified. As with the muscles, assessment of direct tumor involvement with either the lingual or hypoglossal nerve is critical. With these crucial structures in view, the submandibular duct and ganglion are ligated and divided, completing the resection of the submandibular gland and tumor with associated level I nodal tissue ( Figs. 47.2.4, 47.2.5A,B ). The lateral cervical chain lymphatics can then be addressed through this same incision ( Fig. 47.2.5C ).
