29 Primary Malignancies of the Maxilla
Summary
Malignancies of the maxilla include squamous carcinoma and various salivary gland cancers. Various benign tumors also arise. The most common primary therapy is surgery including transoral and open approaches. Surgery of the palate impacts speech and swallowing, so treatment planning must include considerations for complete extirpation and rehabilitation. Neck node metastasis is common and must also be addressed. Multidisciplinary team approach is a key asset.
29.1 Introduction
Malignancy of the hard palate and maxillary alveolus is relatively uncommon. Several histologic types contribute to this group of patients. Surgery is the mainstay of treatment for most cancers in this area. Acceptable extirpation requires expertise in the complex anatomy, cosmetically acceptable surgical approaches, and options for reconstitution of the oral roof. Survival for early cases is good, and quality of life considerations take precedence for those individuals.
29.2 Epidemiology
Squamous carcinoma of the oral cavity roof may be associated with tobacco use, and is also more common in older individuals. 1 The minor salivary cancers have no obvious etiologic risk factors; while ameloblastoma of the maxilla is more common in women, the opposite pattern is seen in mandibular ameloblastoma.
29.3 Clinical Presentation
Squamous cancers of the oral cavity roof most frequently present as a non-healing ulceration or fungating friable carpet of mucosal irregularity (▶ Fig. 28.4). Loosened teeth may be another bellwether symptom. Slowly progressing bone distortion may be the presenting sign for ameloblastoma and other benign bony tumors of the maxilla (▶ Fig. 29.1). Minor salivary gland tumors may present as painless or painful submucosal swelling, particularly at the hard-soft palate junction near the palatine foramen. Other symptoms may include facial numbness (Vth nerve involvement) and diplopia.
29.3.1 Anatomy: Form and Function
The maxilla forms the roof of the oral cavity. Anatomically, it is a relatively simple composite structure, with mucosa covering bone with no substantial submucosal tissue, limited neurovascular structures, and no muscle. The presence of the maxillary dentition perforating the mucosa and anchored in the maxillary alveolus provides the chief topographic and functional complexity. Surfaces may be defined as bucco/labiogingival plate, vertically oriented and projecting upward from the dental structures, and intraoral plate with midline fusion ridge punctuating an otherwise smooth vault of bone. The mucosa of the buccogingival portion is “fixed” immediately above the dental crowns, and is then loose and thin above up to the sulcus of the lip/cheek. The intraoral portion of mucosa is quite thick epithelium, relatively impervious to abrasion and thermal injury by foodstuffs. Blood supply is chiefly comprised of the descending palatine artery, an end branch of the internal maxillary artery of the external carotid system. The neuronal component is purely sensory and provided by the trigeminal nerve, second division (V2). The 16 adult teeth are supplied by an alveolar branch from each side of V2 as well as an alveolar artery. Premolar and first molar teeth roots arise into the floor of the maxillary sinus skeleton, covered by the thin mucosa of the sinus. Canines and incisors are firmly embedded in cortical bone of the premaxilla and nasomaxillary buttress.
The function of the oral maxilla is principally to provide a platform for the oral preparatory phase of deglutition, holding the upper teeth firmly in place and allowing for containment of the oral bolus as it is shifted for the ongoing mastication cycle. The imperforated and bony hard palate keeps food and water out of the nasal cavity and maxillary sinus cavity. A second -function of the hard palate is to form the roof of the oral cavity defining the resonating cavity giving voice its characteristic signature. Maintenance of the labiogingival sulcus is less important for the upper lip than the lower; however, the sulcus is important for cosmetic and dental hygiene reasons.
The maxilla can be divided into two or three structural components for the purposes of surgical and reconstructive planning: the hard palate, the maxillary alveolus, and the bucco/labial maxillary plate. Consideration of these anatomic segmentation may be useful for surgical planning.
29.3.2 Histology
Neoplasms of the oral maxilla are relatively rare, and quite eclectic in histology. While the title of this chapter indicates emphasis on malignancy, benign tumors also arise on the maxilla and present with similar treatment, surgical, and reconstructive challenges. As we have seen, the maxilla is a simple structure comprising bone, teeth, mucosa, and submucosa that contains minor salivary glands in the dense well-vascularized stroma. The neoplasms, therefore, may be of bony, dental, mucosal, and minor salivary gland origin.
Benign tumors of the maxilla include minor salivary gland pleomorphic and monomorphic adenomas, dentigerous lesions including ameloblastoma, bony lesions including fibrous dysplasia, and osteomas. The malignant neoplasms arising on the oral surfaces of the maxilla include squamous cell carcinoma (SCC), minor salivary malignancies (mucoepidermoid, adenoid cystic, adenocarcinoma), and osteosarcoma. Of these, only SCC has a well-established risk profile, being substantially more common in the setting of tobacco abuse, including such activities as inverse smoking (placing the lit end of the cigarette within the mouth). In settings where tobacco use is rare, the other cancer histologies unrelated to known risk factors may comprise a relatively higher proportion of tumors.
The rate of ameloblastoma is four times higher in the mandible than the maxilla, with 60% of maxillary ameloblastomas arising in women. It is important to properly assess the extent of the tumor and achieve complete removal with adjacent normal bone as maxillary ameloblastomas can easily recur high in the skull base and endanger vital structures. Margins of 10-15 mm of normal bone are recommended. The retromaxillary region is particularly difficult to access, requiring a lateral approach through the temporalis muscle region. 2
Sarcomas of the head and neck are located in the maxilla and palate in 13% of cases as per the Head and Neck Sarcoma Registry. 3 Survival rates are good for chondrosarcoma and dermatofibrosarcoma, but poor (< 50% at 5 years) for osteosarcoma, angiosarcoma, and rhabdomyosarcoma. The hard palate is the most common subsite in the oral cavity for adenoid cystic carcinoma (ACC), accounting for 41% of the 1,066 ACC patients in the Surveillance, Epidemiology, and End Results (SEER) review of Dubal. (Dubal) Prognosis for ACC must take into account late recurrences after several decades. The author has followed several patients who developed a mixture of squamous carcinoma and persistent ACC coexisting in the maxillary resection bed 15-20 years after surgery followed by radiation therapy. In these cases, the squamous portion may be attributable to radiation-induced malignancy.
29.3.3 Radiographic Imaging
Documentation of bone destruction is a key goal of radiographic workup of maxillary alveolar and palatal cancers. Minor erosion of the hard palate may be difficult to ascertain with confidence as the bone of the palate has some natural irregularity. Dental films can be helpful in showing minor erosion in the bone surrounding maxillary teeth. CT imaging showing clear bone erosion is indicative of malignant disease along with extension into the pterygopalatine fossa and calcifications within the tumor. 4 The variable intensity of soft tissue demonstrable by MRI can help in distinguishing between tumor and surrounding paranasal sinus inflammation, and may help in focusing attention on certain histologic classes. ACC and B cell lymphomas are associated with homogenous signal intensity while other tumors are more heterogeneous. Post-contrast studies can help further delineate the extent of tumor infiltration. 5
29.4 Treatment
For the vast majority of maxillary tumors, surgery is the mainstay of primary therapy. In part, this is due to the challenges of treating dental tissues directly with primary radiation therapy, particularly the maxilla with its limited soft tissue coverage. Risk of osteoradionecrosis is high when primary radiation is directed at these tissues. In addition, the relatively easy access to the oral cavity through transoral approach allows for direct surgical extirpation.
Tumor extirpation must be accomplished with adequate margins to provide the best opportunity for local control without compromise to function that cannot be managed to re-establish acceptable quality of life. The degree and approach to ablative surgery of the maxilla thus can be highly individualized based on detailed understanding of the complex three-dimensional structure to be addressed. Of course, margins are also required in all dimensions, taking into account complex saddle relationships that are difficult to conceptualize, orient, and catalogue. Exposure must also take into account the instruments such as drills and osteotomes in case they are needed to make bone cuts later. Surgical approach must permit adequate exposure of critical structures with care taken for final cosmesis after closure. The method of reconstruction that is planned will also factor into the choice of approach for extirpation. Truitt and coauthors have categorized surgical management of hard palate malignancies as consisting of alveolectomy, palatectomy, and infrastructure maxillectomy, all feasible through the oral aperature. 6
Structures that are of cosmetic and functional importance must be considered individually to determine if sacrifice is necessary, and if so, how the loss of these will be addressed. Hard palate and dental tissues that allow for mastication and prevent sinonasal penetration can be maintained in some cases. Partial maxillectomy with preservation and primary repair of the hard palate mucosa has been described for highly select tumors of the maxilla. 7 This is most feasible for benign bony lesions and sinonasal cancers. Midface appearance is not altered by removal of bone from the canine fossa, but complete removal of the maxillary-nasal and/or maxillary-zygomatic buttresses will result in change in external contour. Sacrifice of the infraorbital nerve will result in midfacial numbness. Sacrifice of the anterior midline maxilla supporting the nasal vomer and septum can cause tip collapse. Orbital floor and rim are critical to both appearance of the orbit as well as ocular function.
Surgical approach may be divided into transoral and transfacial options and may be supplemented with endoscopic endonasal or intrasinus visualization. The midfacial degloving approach allows for maximal extension of transoral exposure (▶ Fig. 29.2, ▶ Fig. 29.3, ▶ Fig. 29.4, ▶ Fig. 29.5). A variety of facial incisions have been designed to permit exposure with maintenance of acceptable cosmesis. These incisions utilize shadows, creases and grooves, or corners to allow scar to hide or blend while preserving anatomical subunits, muscular continuity and function, and sensation as much as possible. In general, tumors that approach the orbital rim, lacrimal sac, medial canthus, or anterior ethmoid/frontal recess are likely to require a transfacial component. Facial incisions can split the upper lip in midline or along a filtrum ridge with acceptable function and appearance after repair. A group of oral maxillofacial surgeons from China recently reported satisfactory exposure and cosmesis using a lateral lip-splitting approach for access to the maxilla. They maintain that “most of the 36 patients thought their results were good or fair.” 8
The ideal of en bloc resection of the specimen (▶ Fig. 29.6 and ▶ Fig. 29.7) may not always be feasible and should not be prioritized over obtaining adequate margins with acceptable control of hemorrhage. Removal of portions of the specimen sequentially requires that the surgeon keep in mind the original and evolving relationships of tumor and normal borders so as not to miss a component of tumor, while communicating clearly with the pathologist as to the true margin edges for sampling and analysis. This approach also requires attention to integrity of thorough communication and reporting of margins between the surgeon and pathologist.
Hemostasis is a challenge in maxillectomy surgery. The deep positioning of the internal maxillary artery branches necessitates that some bone cuts be made before direct ligation of the distal end is possible. The facial tissues have a very rich blood supply, and so blood loss must be anticipated and prepared for both mentally and practically with blood replacement readily available. Preparation of soft tissues where bleeding may be diminished with vasoconstrictive local injection should be undertaken as much as possible before beginning the osteotomies. Once bleeding begins deep within the bony architecture of the progressively freed maxillary box, it is best to quickly finish the bone cuts without attempts to stop all bleeding in order to attain access to the internal maxillary artery with expediency. Tying off the internal maxillary artery as it branches from the external carotid in the neck or preoperative endovascular embolization may be useful in extraordinary cases of highly vascular tumors. Local injection into the descending palatine foramen of the palate, the posterior aspect of the inferior meatus of the nose where the sphenopalatine artery is located, and in oral and nasal mucosa is also recommended.
29.4.1 Repair
After tumor has been removed, the defect between oral cavity and nose and sinus cavities must be addressed. While it is not life-threatening to experience sinonasal reflux of foods and liquids, this is uncomfortable and unlikely to be acceptable to most individuals if occurring in any quantity. Options for immediate management include gauze packing, placement of temporary obturator, or immediate flap reconstruction. The latter option is the subject of a separate chapter and will not be discussed here. Vaseline and antibiotic-impregnated gauze packing can be conformed to the sinonasal defect and suspended in place with a “spider web” of silk suture placed around the perimeter of the defect. This allows immediate oral alimentation with minimal discomfort while the packing is in place. However, packing must eventually be removed as it is a nidus for bacteria and debris accumulation. We generally leave the packing for 5 to 7 days, during which time prophylactic oral antibiotic is provided. When packing is removed, a further measure for managing the defect must be in view. A quick and inexpensive alternative to gauze packing is the use of comformable thermoplastic (Aquaplast) substance 9 which can be conformed to the remaining skeletal and dental elements, and suspended with wire to the zygoma or with suture to soft tissue. If a dental prosthodontist is part of the team, a more formal obturator may be used. The prosthesis can be fashioned before surgery by taking impressions and planning with the ablative surgeon on how much alveolus and dentition will remain for securing the obturator.
The temporary obturator is then adjusted with soft quick-setting material to fill the soft tissue defect placed intraoperatively. The obturator is then clipped to remaining teeth with clasps incorporated into its design. Wires to bony elements such as pterygoid plates or zygoma, or lag screws to remaining hard palate and vomer complete the fixation. After 1-2 weeks, the obturator is removed and a series of adjustments made by the prosthodontist for comfort and fixing the seal of the device. Fabrication of the final obturator is postponed until the cavity has had time to mature and reach its final endpoint of shape and size. If postoperative radiation is indicated, the fabrication of the final obturator is not recommended until at least 3 months after the completion of radiation.
Placement of a split-thickness skin graft on the raw inner surface of the cheek which remains after sublabial or transfacial incisions before placing the obturator helps prevent cheek and lip contraction with a “snarl” deformity (▶ Fig. 29.8). This also may help with patient comfort during obturator adjustment.
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