Excision of the Submandibular Gland
Randal S. Weber
INTRODUCTION
The principal reasons for excision of the submandibular gland are the presence of refractory sialadenitis or the concern for neoplasia. Prior to embarking upon excision of the submandibular gland, it is incumbent upon the surgeon to ascertain the diagnosis of the salivary gland pathology present so that the surgery may be tailored appropriately. Submandibular sialadenitis may be idiopathic or secondary to chronic sialolithiasis. Neoplasia, on the other hand, comprises a wide spectrum of heterogeneous tumors that may be benign or malignant.
A detailed history and physical examination are important for differentiating chronic inflammatory disease from a neoplasm. Preoperative imaging studies and the use of fine-needle aspiration biopsy will provide diagnostic information for achieving the appropriate preoperative diagnosis.
The surgical approach is quite different depending upon whether the surgeon is dealing with a chronic inflammatory process or neoplasia. To avoid inappropriate or inadequate surgery, the surgeon must achieve a working diagnosis prior to excision. Table 31.1 displays our experience with tumors of the submandibular gland and the histologic spectrum of malignancy. Benign neoplasms include pleomorphic adenoma, monomorphic adenoma and benign lymphoepithelial lesion.
For a chronic inflammatory process, an extracapsular dissection and a capsular excision of the submandibular gland is adequate, whereas for suspected neoplasia, the minimal surgical procedure should be a complete dissection of levels IA and IB. Thus, appropriate preoperative planning and differentiating between sialadenitis and neoplasia of the submandibular gland are critical to avoid an inadequate operation should a neoplasm be the underlying pathology.
HISTORY
A complete history will assist the clinician in achieving the correct diagnosis. For patients with chronic sialadenitis, typical symptoms includes intermittent swelling of the submandibular gland often exacerbated by eating or drinking. Over time, the gland may become firm, fibrotic, and chronically painful. There may be a history of sialoliths that have been removed transorally. In severe cases of sialadenitis, abscess formation may have occurred in the past. Conversely, in patients with submandibular gland neoplasia, gradual enlargement is typical. For instance, in patients with a pleomorphic adenoma of the submandibular gland, enlargement may have occurred over several years. For those with malignant tumors, progressive enlargement generally occurs over a shorter interval. Pain may be a symptom in patients with an acute relapse of sialadenitis. For patients with benign neoplasms of the submandibular gland, pain is an uncommon symptom. In up to 20% of patients with malignant tumors of the submandibular gland, pain may be constant and progressive. Cranial nerve palsies, including weakness of the lower lip, numbness of the tongue or paresthesias, and paralysis of the hemitongue, may occur in patients with malignant tumors. Inquiry into the presence or absence of these symptoms is important.
TABLE 31.1 Histologic Distribution of Submandibular Gland Carcinomas | ||||||||||||||||||||||
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PHYSICAL EXAMINATION
Physical examination for patients with submandibular gland enlargement should include inspection and palpation of the neck as well as the oral cavity. The size and consistency of the gland should be documented, as should the presence or absence of tenderness and whether or not the gland is mobile. The important cranial nerves assessed include the marginal mandibular branch of the facial nerve; the lingual nerve, which provides sensation to the ipsilateral oral tongue; and the hypoglossal nerve, which provides motor innervation. Involvement of the hypoglossal nerve may be manifest by atrophy of the hemitongue, fasciculations, or deviation on protrusion of the tongue to the side of the paralysis. The presence or absence of trismus should be assessed and, if present, is indicative of invasion of the medial pterygoid muscle. With the mouth open, the submandibular gland should be palpated and massaged to determine if saliva can be expressed from the Wharton duct. Bimanual palpation of the floor of the mouth and submandibular gland is important and may indicate the presence of a stone in the submandibular duct. Bimanual palpation will also provide an estimate as to the size of the gland, an indication as to fixation of the gland to the mandible or surrounding structures. Palpation for enlarged lymph nodes is critical and, if adenopathy is present, supports the presence of malignancy. The presence of lymphadenopathy in the upper neck should raise a concern that one is dealing with a malignant tumor of the submandibular gland, especially if present in level I along with enlargement of the gland.
INDICATIONS
Surgery for excision of the submandibular gland has two broad indications. The first is for chronic inflammatory disease that includes certain patients with sialoliths, and the second is for suspected neoplasia. In patients with chronic inflammatory disease, repeated painful swelling of the gland during stimulated salivation is usually not alleviated by medical treatment, and surgical excision should be considered. These patients may or may not have sialoliths. Occasionally salivary stones are in the most proximal portion of the Wharton duct and are not amenable to removal with sialendoscopy or sialodochotomy. In these cases, excision of the gland and the proximal portion of the duct harboring the stone is indicated. For patients with a history of submandibular gland infection and abscess, excision should be performed following an interval to allow the acute inflammation to subside.
Patients with suspected neoplasia should be considered for surgery. The minimal surgery for a neoplasm of the submandibular gland is a level I dissection that removes the gland and the facial lymph nodes. Enucleation of the gland should be avoided in these cases to avoid incomplete excision of tumor.
CONTRAINDICATIONS
A contraindication to surgical removal of the submandibular gland for patients with either salivary stone or chronic inflammatory disease is lack of adequate conservative therapy. Stone removal by endoscopic or transoral procedures should be performed as a first step when feasible. For recurring sialadenitis, hydration, oral antibiotics, and sialogogues should be given a trial to alleviate symptoms. When neoplasia is suspected, the principal contraindication to surgical removal would be the patient’s inability to tolerate general anesthesia.
PREOPERATIVE PLANNING
Imaging Studies
Imaging studies may be performed prior to excision of the gland. A computed tomography (CT) scan with contrast will provide information regarding involvement of the mandible, the presence or absence of pathologic lymphadenopathy, and the local extent of the tumor. Submandibular sialoliths are radiopaque in 80% of patients when present. The gland may demonstrate enlargement and diffuse enhancement in cases of chronic inflammatory disease. As with parotid neoplasms, imaging lacks specificity for differentiating benign from malignant tumors. Magnetic resonance imaging (MRI) scanning will provide soft tissue detail superior to CT scans and may demonstrate enhancement of the lingual or hypoglossal nerves or enlargement of the neural structures that would raise suspicion for malignancy. At times, both modalities may be helpful when evaluating a patient with a malignant tumor.
Fine-Needle Aspiration Biopsy
Fine-needle aspiration biopsy is a useful tool for differentiating chronic inflammatory disease from neoplasia. In patients with chronic sialadenitis, cytologic examination will typically demonstrate the presence of acute and chronic inflammatory cells. In contrast, however, fine-needle aspiration for patients with neoplasms will demonstrate the presence of neoplastic cells, but differentiating benign from malignant tumors is more difficult. Nevertheless, an experienced cytopathologist will accurately differentiate inflammation from neoplasia in 85% to 90% of cases. Ultrasound-guided fine-needle aspiration biopsy should be employed when anatomic imaging demonstrates areas of heterogeneity in the gland suspicious for neoplasia. This will improve the accuracy and the diagnostic utility of fine-needle aspiration biopsy. Finally, if enlarged lymph nodes were present, fine-needle aspiration biopsy may confirm the presence of regional metastasis.
Table 31.2 provides an algorithm for differentiating benign inflammatory conditions from a neoplastic process.
Informed Consent
Prior to embarking on surgery, the risks of the procedure should be carefully explained to the patient. The usual risk factors include general anesthesia, bleeding, and infection. Due to the proximity of important cranial nerves in the operative field, the patient should be apprised of the possibility of weakness of the lower lip, numbness of the tongue, or paralysis of the tongue on the operated side due to injury to the marginal mandibular, lingual, and hypoglossal nerves, respectively.
SURGICAL TECHNIQUE
The surgical approach differs depending upon the diagnosis of sialadenitis versus neoplasia. The former requires a limited incision and essentially an extracapsular removal of the submandibular gland with preservation of all nerves in the region. Conversely if one is excising either a benign or malignant neoplasm,
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