Cancer of the floor of the mouth

Patches of thin homogeneous leukoplakia are usually observed (intervention on possible causal factors, including tobacco/alcohol use, chronic trauma, and alimentary habits, as well as biopsy is performed if areas becomes symptomatic or if appearance changes [eg, development of a grossly irregular surface with or without erythroplakia], and malignancy is suggested). Premalignant lesions of the mucosa of the oral cavity such as hyperkeratosis, dysplasia, and even carcinoma in situ can be treated by peroral excision, if it is localized and of a relatively small extent (Figure 1). On the other hand, diffuse or multifocal lesions involving a large surface area preclude complete conventional excision. The carbon dioxide laser is an effective method for excision or vaporization of such lesions. The desired depth of tissue destruction for leukoplakia is approximately 1 to 2 mm in thickness. Complete hemostasis is obtained by controlling focal bleeding points by defocusing the laser beam. Radiation therapy plays no role in the treatment of premalignant lesions of the oral cavity.

Similar to cancer of the oral tongue, small FOM cancers may be treated effectively with either radiation therapy or surgery, with equivalent cure rates of 70% to 95%.^,  The proximity of the mandible and the risks of radiation-induced bone and soft tissue necrosis, in addition to severe xerostomia, are the main reasons for selecting surgery in the majority of cases. The mandible is considered at risk when the primary lesion overlies the mandible. If the lesion extends to the gingiva without fixation to the periosteum, the resection should include the periosteum and spare the mandible. In cases of lesions adherent to the periosteum, a rim of mandible should be included in the specimen (Figure 2). As a general rule, early invasion of the mandible can be treated by marginal mandibulectomy, because the cortical part of the mandible inferior to the roots of the teeth remains uninvolved and can be spared safely. In edentulous patients, the feasibility of marginal mandibulectomy depends on the vertical height of the body of the mandible (Figure 3a and b). The involvement of the narrow lateral FOM is less common.

The majority of these lesions involve the gingiva and are tethered or fixed to the mandible. Rim resection, whenever possible, preserves continuity of the mandible and offers acceptable speech and swallowing in addition to a good cosmetic result (Figure 4, Figure 5). Preoperative irradiation is not advisable in these cases, because of the high risk of pathological fracture or osteoradionecrosis, particularly in elderly patients. Patients who have tumors staged T4 only because of bone invasion have a better chance of cure compared with those with large, infiltrative tumors grossly involving the suprahyoid musculature or with deep infiltration of the tongue. Radical surgery of the primary tumor with segmental mandibulectomy and partial or subtotal glossectomy, combined with adjuvant radiation therapy, is the preferred modality of treatment. Reconstruction of the mandible and soft tissues are better achieved through a composit osteocutaneous free flap (usually with iliac crest or fibula). Postoperative radiation portals often include the entire oral tongue and FOM with a total tumor dose ranging from 6500 to 7000 cGy (daily dose of 180 cGy). Clinically positive cervical nodes are managed by a small field boost of radiation with a dose ranging from 4500 to 5000 cGy after neck dissection. Acute mucositis, with debilitating effects on the patient, should be expected. The current indications for segmental mandibulectomy in FOM include the following: (1) tumors extending up to the alveolar process in elderly edentulous patients in which marginal mandibulectomy is not feasible; (2) gross invasion by the oral cancer; (3) invasion of the inferior alveolar nerve or canal by the tumor; and (4) massive soft tissue disease adjacent to the mandible. Palliative treatment has usually been radiation therapy with two fractions of 1000 cGy delivered at a 7- to 10-day interval.

Peroral excision for small superficial lesions of the FOM can be performed with the surgical defect safely left open to granulate and heal by secondary intention. However, when such an excision includes deep portions of the FOM reaching the underlying musculature, or when the lesion is located in certain critical areas where mobility is essential, secondary healing leads to fibrosis and contracture impairing function. In these cases, immediate coverage of the surgical defect is indicated (Figure 10). Under general anesthesia and naso-tracheal intubation, the oral cavity is exposed and opened with a self-retaining mouth retractor. Packing the oropharynx with a humid gauze bolster is advisable to prevent aspiration during the procedure. The proposed area of surgical excision is marked out with the electrocautery to obtain adequate surgical margins. A 3-dimensional resection of the primary tumor is performed, with care taken not to disrupt the surgical specimen, which makes it difficult to evaluate the surgical margins at the frozen-section examination. As the Wharton’s ducts become visible, they are obliquely transected (to provide a wider opening) and the ducts’ posterior halves are anastomosed to the remaining mucosa of the FOM with interrupted absorbable 4-0 sutures on its posterolateral aspect. A full-thickness skin graft is harvest from the supraclavicular area of the neck or from the inguinal/abdominal area (if its a hairless area) and, after appropriately trimmed, it is sutured to the mucosal edges of the surgical defect with absorbable 3-0 sutures. Anastomosis of the anterior halves of the Wharton’s ducts is then accomplished. After the graft is sutured in place, several stab incisions are made in the skin graft to permit drainage of blood and/or serum that may accumulate beneath the graft. A Xeroform gauze bolster is made to fit the area of the skin graft and is anchored in position with 2-0 silk tie-over sutures. The nutritional intake will be provided by a nasogastric tube for approximately 1 week (period of boslter dressing use). Intense oral irrigations and rinses with saline solution are advisable to maintain optimal oral hygiene, even after the removal of the bolster dressing. Feeding by mouth will be made initially with clear liquids and pureed foods. Even when skin grafts do not take completely, they still play an important role in providing a biological dressing of the surgical defect in the immediate postoperative period (Figure 11, Figure 12). Other options for FOM reconstruction with locoregional flaps include the following: (1) nasolabial flap, (2) tongue flap, and (3) platisma flap.

Excision of moderately advanced FOM tumors usually requires wide exposure for access to the primary tumor and satisfactory resection. A lower cheek flap approach or a visor flap approach is indicated, depending on the location of the primary tumor. The lower cheek flap approach involves splitting the lower lip and the chin in the midline through its full thickness up to the symphysis of the mandible. The incision continues in the midline up to the thyrohyoid membrane, where it turns toward the ipsilateral neck along an upper skin crease. This transverse component of the incision should be at least two fingerbreadths below the body of the mandible to prevent inadvertent injury to the mandibular branch of the facial nerve during elevation of the cheek flap (Figure 13). With the visor flap approach, the oral cavity is exposed via a single transverse skin incision extending from the mastoid process on one side to that on the other side, along an upper neck skin crease. The visor flap requires another incision in the gingivobuccal and gingivolabial mucosa with division of all soft tissue lateral to the mandible, permitting elevation and retraction of the visor flap to expose the oral cavity (Figure 14). The operative procedure planned for a moderately advanced FOM cancer consists of a neck dissection (bilaterality and extent of the procedure depends on the location of the primary tumor and the presence or absence of lymph node metastases) together with marginal resection of the mandible and resection of the FOM. The neck dissection is completed in the usual fashion except for level I, through which the specimen is attached to the primary tumor. All attachments of the specimen inferior and deep to the digastric tendon are divided at this point. The upper neck flap is already elevated, with careful identification and preservation of the mandibular branch of the facial nerve. The periosteum of the body of the mandible is exposed, and a close-up view of the primary tumor and its limits with the lingual surface of the mandible and with the other intraoral structures facilitates the planning of 3-dimensional resection. To outline the extent of intraoral mucosa to be resected, an incision is made in the mucosa of the undersurface of the tongue, extending from the alveolar process of the body of the mandible from one side to another, keeping a generous cuff of normal mucosa around the primary tumor. The musculature is completely divided, and a power saw is used for marginal mandibulectomy. This specimen should include the alveolar process and as much of the lingual plate of the mandible as possible, which is made through an oblique cut. Such an oblique cut permits resection of the musculature attached to the mandible in a monobloc fashion. With a skin hook, the portion of the mandible to be resected is elevated from the body of the mandible, revealing the deep muscular attachments to the genial tubercle and other parts of the mandible. At this point, a more precise evaluation of the tumor borders (and their relation to the mandible) is possible, confirming or not the indication for marginal resection instead of segmental resection. The remaining soft tissue attachments between the surgical specimen and the patient are detached with an electrocautery at this point. The excised specimen, in a monobloc fashion, should include a marginal mandibulectomy and through-and-through resection of the FOM, in continuity with the cervical lymph nodes excised by neck dissection. Frozen sections are obtained from appropriate areas of the surgical field. The goals of reconstruction for intraoral defects include covering the exposed area of muscle and bone, releasing the tongue and restoring its mobility for speech, mastication, and swallowing. Primary closure can be used if it does not cause tethering of the tongue. Alternative methods of reconstruction include the following: (1) skin grafts, (2) nasolabial flaps, (3) platisma flap, and (4) radial forearm flap. If adequate vertical height of the marginally resected mandible is available, the patient should be considered for secondary placement of osseointegrated dental implants and a permanent fixed denture. A tracheostomy is usually necessary and us performed at the conclusion of the operation for provision of a satisfactory airway and to facilitate clearance of pulmonary secretions.