The soft palate is a subsite of the oropharynx. Its axial plane defines the superior boundary of the oropharynx, incompletely separating it from the nasopharynx above. The soft palate comprises approximately one-third of the palate, with the more anteriorly positioned hard palate making up the remainder; the junction between the hard and soft palates also separates the oral cavity from the more posteriorly located oropharynx. In contrast to the hard palate, the soft palate is a mobile structure that is suspended from the posterior aspect of the hard palate via the palatine aponeurosis. This aponeurosis is formed by the expanded tendon of the tensor veli palatini. The thicker, anterior portion of this tendon constitutes the majority of the anterior soft palate, whereas the posterior aspect of the soft palate is mainly comprised of muscle (levator veli palatine, tensor veli palatini, palatoglossus, palatopharyngeus). At its most posteroinferior extent, the free margin of the soft palate contains a conical muscular projection, the uvula. Functionally, the soft palate is a dynamic structure that is critical for velopharyngeal competence. Elevation of the soft palate puts it into contact with the posterior pharyngeal wall, sealing it off from the nasopharynx (e.g., when swallowing), and its depression puts it in contact with the tongue base, sealing the oral cavity from the nasal passage (e.g., when breathing exclusively through the nose). In this way, function of the soft palate is critical to velopharyngeal competence.
Neoplasms of the soft palate may arise from any of the individual, constituent parts of the soft palate (muscle, lymphatics, mucosa, connective tissue), encompassing a broad variety of benign and malignant tumors ( Table 37.1 ). Importantly, benign tumors of the soft palate are extremely rare, and any soft palate lesion should be considered malignant until proven otherwise. Squamous cell carcinoma is the most common neoplasm of the soft palate, and the oropharynx in general, accounting for more than 90% of all malignant tumors in the oropharynx ( Fig. 37.1 ). Etiologic factors contributing to squamous cell carcinoma are alcohol and tobacco. Although the human papillomavirus (HPV) has more recently been established as an etiologic and positive prognostic factor for oropharyngeal squamous cell carcinoma, a recent review has suggested that significantly less soft palate squamous cell carcinomas are HPV positive than other subsites (22% vs. 70%).
| Benign | Malignant |
|---|---|
| Fibroma | Adenocarcinoma |
| Hemangioma | Adenoid cystic carcinoma |
| Lipoma | Lymphoma |
| Papilloma | Mucoepidermoid carcinoma |
| Pleomorphic adenoma | Mucosal melanoma |
| Schwannoma | Squamous cell carcinoma |
A tumor of salivary gland origin represents the next most commonly encountered tumor of the soft palate, originating in the many minor salivary glands distributed throughout the soft palate. Although the most common benign salivary gland tumor of the soft palate is pleomorphic adenoma, it is estimated that nearly 50% of minor salivary gland tumors in the oropharynx are malignant. The most common of these malignancies are adenoid cystic carcinoma and mucoepidermoid carcinoma. In contrast to the mucosal disruption caused by typical squamous cell carcinomas, minor salivary gland tumors are frequently submucosal.
Lymphatic drainage of the soft palate is primarily to the superior jugulodigastric chain (level II) with subsequent drainage inferiorly to levels III and IV. Importantly the retropharyngeal lymph nodes also receive significant drainage from the soft palate, with one study demonstrating retropharyngeal node involvement of carcinoma in 56% of cancers of the soft palate. Cancers of the soft palate also have a high incidence of metastases to the cervical lymph nodes, with one study demonstrating that 48% of patients with cancer of the soft palate present with metastases to the neck and another 40% who initially presented with an N0 neck who eventually went on to develop cervical lymph node metastases. Because of this, all patients with clinically negative necks still require treatment with either an elective neck dissection or radiation, with bilateral neck dissection required for lesions involving or approaching the midline.
Key Operative Learning Points
- 1.
The soft palate is a dynamic structure whose function is critical for velopharyngeal competence.
- 2.
There is a high incidence of cervical lymph node metastasis associated with cancer of the soft palate (particularly with squamous cell carcinoma). Treatment of both necks is recommended for squamous cell cancers involving or approaching the midline.
- 3.
Reconstruction of the soft palate is complex, and reconstitution of a functional velopharyngeal sphincter is key.
Preoperative Period
History
- 1.
History of present illness
- a.
Symptoms range widely from asymptomatic to odynophagia, dysphagia, otalgia, airway compromise, oral bleeding, weight loss, changes in speech, and a mass in the neck.
- b.
Early lesions are often found incidentally due to dental examinations, ill-fitting dentures, and office physical examinations but also may present at more advanced stages.
- c.
Patients may have hearing loss due to middle ear effusion secondary to Eustachian tube dysfunction.
- a.
- 2.
Past medical history
- a.
Prior history of malignancies and treatment
- b.
Anticoagulant medications
- a.
- 3.
Social history
- a.
Tobacco use history (all types)
- b.
Alcohol use history
- a.
Physical Examination
- 1.
All patients should undergo a comprehensive examination of the head and neck.
- a.
Thorough inspection and palpation of the oral cavity and oropharynx
- b.
Neck: assessment for cervical lymph node metastases
- c.
Laryngoscopy/pharyngoscopy: assessment posterior/inferior extent of lesion, evaluation of larynx/hypopharynx, evaluation for second primary malignancy, evaluation of airway patency
- d.
Cranial nerve examination: evaluation of palatal elevation (CN X)
- a.
- 2.
The primary tumor should be evaluated with respect to location and extension into surrounding structures.
- a.
Size of the lesion, local extent (e.g., involvement of adjacent subsites), firmness to palpation, mobility, endophytic versus exophytic, oral airway obstruction
- b.
A neoplasm isolated to the posterior/nasopharyngeal surface of the soft palate is exceedingly rare.
- c.
Mouth opening should be evaluated because trismus and oral airway obstruction by tumor may preclude a transoral resection or intubation.
- a.
Imaging
Computed tomography (CT) and magnetic resonance imaging (MRI) are frequently used for delineation of local extent of tumor (T-stage) and evaluation for cervical metastases; (Fluorodoxyglucose-Positon Emission Tomography/Computerized Tomography FDG PET/C) is used to evaluate for distant metastases.
- 1.
CT with contrast: primary imaging modality for head and neck cancer; gives excellent delineation of involvement of adjacent bony structures (palate, mandible)
- 2.
MRI with contrast: enhanced soft tissue resolution allowing better delineation of depth of invasion and evaluation of perineural invasion. Although MRI has a greater potential for motion artifact, dental artifact is usually significantly less than with CT.
- 3.
FDG PET/CT: improved sensitivity over CT or MRI alone in detecting metastases greater than 5 mm. The negative predictive value of PET/CT is nearly 100% for second primary tumors and metastatic disease.
Indications
- 1.
Early-stage (T1-T2) squamous cell carcinoma with minimal involvement of soft palate musculature
- 2.
Advanced (T3-T4) cancer of salivary gland origin
- 3.
Salvage surgery for persistent/recurrent cancers (salvage is typically successful in only ⅓ of patients)
Contraindications
- 1.
Advanced (T3-T4) lesions requiring resection of a significant portion of the soft palate musculature (exception: patients who are not candidates for or who have already received definitive radiation)
- 2.
Patients with distant metastases or large/unresectable cervical lymph node metastases
- 3.
Proximity to large vessels to or involvement of primary tumor (i.e., medialized course of carotid artery or tumor adjacent to carotid artery)
- 4.
Patients with significant trismus or oral contractures limiting access for a transoral resection (transcervical resection may still be possible)
- 5.
Patients medically unfit to undergo general anesthesia (rare)
Preoperative Preparation
- 1.
Biopsy of the lesion should be performed for adequate diagnosis prior to any definitive resection.
- 2.
Evaluation for metastasis should be completed preoperatively.
- 3.
Discussion of surgery with a complete explanation of risks/benefits/alternatives
- a.
Risks: bleeding, infection, need for additional surgery and/or adjunctive treatments, velopharyngeal incompetence
- b.
Benefits: tumor excision, pathologic staging, possibility of avoiding radiation therapy and/or chemotherapy in some cases
- c.
Alternatives: Radiation ± chemotherapy depending on tumor stage. Not effective in tumors of salivary gland origin.
- a.
- 4.
Patients should be aware of the possibility and expected duration of a tracheostomy and/or placement of a feeding tube.
- 5.
Patient should be seen in consultation with a Maxillofacial Prosthodontist with possible fabrication of a prosthesis.
Operative Period
Anesthesia
General anesthesia is typically required for patient comfort and airway protection.
Positioning
Supine with shoulder roll placement reserved for concurrent neck dissection or the rare transcervical approach
Perioperative Antibiotic Prophylaxis
Clean-contaminated surgery with recommendation for ampicillin/sulbactam or clindamycin, cefazolin which should be given prior to skin incision and then continued for no more than 24 hours
Monitoring
Although muscle relaxant (i.e., paralysis) is often required for transoral resections, some surgeons prefer the patient nonparalyzed during concurrent neck dissection or the rare transcervical approach to enable nerve assessment.
Instruments and Equipment to Have Available
- 1.
Mouth retractor: Crowe-Davis, McIvor, Dingman, and Feyh-Kastenbauer can all be used depending on patient factors (mouth opening, dentition, tumor location) and surgeon’s preference.
- 2.
Standard head and neck and oral surgery set
- 3.
Cautery: Bovie electrocautery may be used for excision with suction cautery, and/or bipolar cautery is often required for hemostasis.
- 4.
Adjunctive equipment:
- a.
Robotic platform (da Vinci System) for transoral robotic surgery (TORS)
- b.
CO 2 laser (±microscope) for transoral laser microsurgery (TLM)
- a.
Key Anatomic Landmarks
- 1.
Tonsillar pillars: Formed by the paired palatoglossus (anterior) and palatopharyngeus (posterior) muscles, these muscles form lateral connections of the soft palate to the tongue base and pharynx, respectively. These also serve as routes of extension of tumor onto the pharyngeal wall, tonsil, and base of tongue, which is important in surgical planning.
- 2.
Hard/soft palate junction: defines the anterior boundary of the oropharynx and serves as the attachment point for the palatine aponeurosis, into which all four paired muscles of the soft palate insert (palatoglossus, palatopharyngeus laterally; levator veli palatini and tensor veli palatini centrally)
- 3.
Lesser palatine artery: paired arteries arising from the lesser palatine foramina in the posterior hard palate that supply the soft palate
- 4.
Uvula: conical, muscular projection from the free margin of the posteroinferior extent of the midline soft palate
Prerequisite Skills
If undertaking TLM or TORS, the surgeon must be experienced with these modalities.
Operative Risks
- 1.
Bleeding
- 2.
Infection
- 3.
Dysphagia
- 4.
Velopharyngeal incompetence
- 5.
Need for additional procedures or treatment modalities
Surgical Technique
- 1.
Ablation: Transoral resection is the rule for most isolated cancers of the soft palate. Extended, transcervical approaches to the oropharynx (i.e., cheek flap, mandibulotomy with lip split) are rarely required for isolated cancer of the soft palate but may be necessary for larger/composite resections or in patients with severe trismus limiting transoral exposure. It is critical to have a three-dimensional (3D) understanding of the tumor, and larger tumors require margins to be achieved in both the oropharynx and the nasopharynx. Ideally, the posterior nasopharyngeal margins are directly visualized. Resection of the cancer should be performed with at least 1-cm margins of normal tissue with margins verified by frozen section. The incisions in the oropharyngeal mucosa are made first with any deeper, muscular or nasopharyngeal mucosal resection dictated by the extent of the tumor. Larger cancers will often require a through-and-through defect, whereas in more superficial lesions, the posterior soft palate can be preserved. Given the high prevalence of regional metastasis, all patients with squamous cell carcinoma should undergo unilateral neck dissection (levels II to IV), with bilateral neck dissection performed for patients with larger cancers in or approaching the midline. The transoral resection may be performed with multiple modalities according to patient factors and surgeon’s preference:
- a.
Transoral electrocautery: traditional method using handheld electrocautery; access and visualization may be limited by short working distance of the instruments
- b.
TLM: improved visualization enabled by the use of a microscope and longer working distance of the laser. This modality has been shown to be effective in both primary and salvage resections.
- c.
TORS: affords 3D visualization with 10-fold magnification and an operation using two fully articulated instruments; outcomes are reliant on surgeon experience, but the modality has been proven effective with high local control and low morbidity
- d.
Transcervical/transmandibular approaches: rarely used for isolated defects of the soft palate; may be required for larger, composite defects of the oropharynx or in salvage situations in patients with significant trismus
- a.
- 2.
Reconstruction: Functional reconstruction of the soft palate is complex, owing to its important role in speech and swallowing. The best results are obtained with small defects wherein the musculature of the soft palate is minimally resected and can be reapproximated. If the defect extends beyond the midline of the soft palate, reconstruction typically involves reducing the cross-sectional area of the velopharynx.
- a.
Primary closure: best for smaller, superficial defects (commonly submucosal cancer of minor salivary gland origin). Accomplished by approximating oropharyngeal mucosa to posterior/nasopharyngeal mucosa on either side of the defect (similar to a uvulopalatopharyngoplasty). Healing by secondary intention is also possible for small defects but may result in wound contraction and velopharyngeal insufficiency (VPI).
- b.
Obturation: best suited to smaller defects of the central palate. Adequate remaining dentition is necessary to anchor the prosthesis. It is also an option for patients who are not candidates for large reconstructive efforts. The prosthesis allows nasal breathing at rest but contacts the posterior pharyngeal wall to enable velopharyngeal closure during swallowing. Studies have shown equivalent speech outcomes between obturation and free flap reconstruction for extensive soft palate defects.
- c.
Local flaps: The uvulopalatal flap, pharyngeal flap ( Fig. 37.2 ), palatal island flap, and the superior constrictor flap have all been described and are best for defects of less than 50% of the lateral palate.
- a.
