Disclaimer: The information contained within the Grand Rounds Archive is intended for use by doctors and other health care professionals. These documents were prepared by resident physicians for presentation and discussion at a conference held at Baylor College of Medicine in Houston, Texas. No guarantees are made with respect to accuracy or timeliness of this material. This material should not be used as a basis for treatment decisions, and is not a substitute for professional consultation and/or peer-reviewed medical literature. Maxillary Ameloblastoma Ameloblastoma is a histologically benign, locally aggressive tumor arising from the odontogenic ectoderm. It accounts for one percent of all oral tumors. The mandible is affected four times more frequently than the maxilla. Both sexes are affected equally. Although the tumor can occur at any age and has been described in the literature in patients as young as 21 months, most patients present in the third or fourth decade of life. In the mandible, there is a predilection for the molar-ramus area with a little more than two-thirds occurring in this region. This also the most common region in the maxilla. The tumor is relatively uncommon anteriorly. Typically, early symptoms are absent and these tumors are seldom diagnosed in the early stages of development. The usual clinical presentation of this tumor is that of a slowly growing, asymptomatic intraoral swelling. This is the case in about 75 percent of patients. Pain, numbness, toothache, mobile teeth, ill-fitting dentures, malocclusion, ulcerations, draining sinuses, nasal obstruction, or even epistaxis may bring the patient to seek medical advice. Pathological fracture is a very unusual finding on presentation. They are often found incidentally with the use of routine dental x-rays. It is interesting to note that some authors have reported that trauma, infection, or previous extraction was documented in 60-70 percent of patients ultimately shown to have ameloblastoma. The diagnosis of ameloblastoma cannot be made by radiographic means alone. There are, however, several radiographic features which make one suspicious of the diagnosis. As it begins within the jaw and grows slowly, it expands the lingual cortex. Radiographically, this translates to a radiolucency which when unilocular is difficult to distinguish from a simple odontogenic cyst. Nearly one-half of all ameloblastomas exhibit an overlapping multilocular soap-bubble or honeycomb appearance. The margins of the defect are scalloped and well defined in the majority of cases. Uneven cortical sclerosis at the margin of the tumor has been described as typical. When the tumor occurs adjacent to a tooth, the root of the tooth is typically eroded whereas displacement of teeth is more common in association with simple dentigerous cysts. The differential diagnosis of a multilocular radiolucency in the jaw in-cludes cherubism, giant cell granuloma, odontogenic myxoma, aneurysmal bone cysts, odontogenic keratocysts, and others, and often the diagnosis is not made until the patient undergoes diagnostic biopsy. Microscopically, the ameloblastoma is composed of nests, strands, and cords of ameloblastic epithelium, all separated by relatively small amounts of fibrous connective tissue stroma. There are two predominant patterns: follicular and plexiform. In the follicular form, the epithelial islands contain central portions that are composed of a loose network resembling that of the enamel organ. The epithelium at the periphery is composed of tall columnar cells with polarized nuclei. In the plexiform type, the epithelium is arranged in anastomosing strands and cords. The epithelial cells are closely apposed and appear basaloid or cuboidal. Muller and Slootweg looked at the growth characteristics of ameloblastoma histologically and the reaction of the surrounding tissues in 31 surgical specimens. They reached four primary conclusion: 1) Infiltration of spongy bone is seen frequently. 2) There is little tendency for invasion of cortical bone. 3) The periosteum generally forms a barrier against tumor growth. 4) No definite capsule can be seen where the tumor adjoins the oral mucosa. These conclusions led to several inferences regarding the management of these tumors. They felt that: 1) Spongy bone needed to be resected at some distance from the tumor margins and they recommended a one centimeter margin of apparently healthy bone to ensure adequate resection. 2) Cortical bone should be resected sparingly. 3) Mucosa overlying the alveolar process enclosing the perforated bone must be included in the resection. Although histologically indistinguishable, maxillary ameloblastomas are considered more aggressive and are more difficult to treat because the thick compact bone found in the mandible which confines tumor growth is not found in the maxilla. The combination of thin fragile bone with the proximity of the maxilla to the nasal cavity, paranasal sinuses, orbit and vital structures at the base of skull add a clinical dimension not present with mandibular tumors. Peripheral ameloblastoma is defined as tumors that demonstrate the histologic characteristics of their interosseous counterparts but occur solely in the soft tissue covering the tooth-bearing portion of the jaws. In contrast to central ameloblastomas, peripheral lesions do not exhibit aggressive destructive behavior and do not invade the underlying bone. These lesions require excision with minimal margins and rarely recur. Metastatic ameloblastoma is rare. The most common sites were lung, pleura, lymph nodes, and bone. Certain clinical situations, including: 1) long duration of tumor, 2) multiple recurrences, 3) extensive local disease, 4) frequent surgical procedures, and 5) radiation therapy, have been implicated as risk factors. Both the primary and distant lesions are histologically benign and the mechanism of spread is debated. Some suggest lymphatic or hematogenous spread while others support aspiration of tumor cells, citing as evidence that the most common site is the lung, which provides a fertile ground for displaced cells. No standard treatment has been established for these tumors. A variety of modalities have been tried including local curettage, cryotherapy, cautery, laser, simple excision, radical excision, radiotherapy, and chemotherapy. A surgical approach is generally accepted as the treatment of choice, but there is no consensus regarding conservative versus radical surgery. Some authors state that it is important to distinguish between unilocular and multilocular lesions because unilocular lesions are slower growing and less infiltrative and may be managed more conservatively with curettage. Muller and Slootweg believe this is a fallacy because those publications fail to make allowances for the slow growing pattern and do not give long-term follow-up. Sehdev and others quote a 90% recurrence rate for mandibular lesions following treatment by curettage, 20% recurrence after segmental resection, and 20% recurrence after salvage of previously curetted lesions by segmental or hemimandibulectomy. In the maxilla, Sehdev reported 100% recurrence in 11 patients treated by curettage. En bloc excision with margin of normal tissue provided a recurrence rate of 22%. Some investigators have reported palliation following irradiation. Dosages range from 45 to 60 Gy, with regression or control of disease in half or less of patients in most reports. There have also been reports of sarcomas induced when treating ameloblastomas with radiation. There are few references in the literature of chemotherapy in the treatment of this tumor. In most cases, it has been used as a last resort and none of the agents used have proven effective. SUMMARY Ameloblastoma is a histologically benign but locally aggressive tumor with a marked tendency for recurrence. In rare instances it has been known to act in a malignant fashion. Most patients present with an asymptomatic mass. Radiographic findings are not pathognomonic but usually reveal a uni- or multiloculated expansile lesion which thins bone and may have scalloped borders with a smooth contour. The mainstay of therapy is surgical excision with adequate margins. Simple curettage is associated with unacceptable recurrence rates. Case Presentation A 55-year-old man from Mexico had a loose right maxillary third molar extracted six months prior to admission. The wound healed poorly and bled intermittently. He subsequently underwent right Caldwell-Luc through which a soft tissue mass in the maxillary sinus was biopsied. The provisional diagnosis was benign cystadenoma. He was referred to the United States and our service for further evaluation and management. Examination revealed a soft tissue mass extending into the right nose from the middle meatus. Panorex was obtained and demonstrated a destructive lesion involving the right lateral aspect of the maxillary alveolar ridge. CT depicted a well defined, lobulated, partially cystic mass centered on the right maxillary alveolar ridge. Histopathologic review of the biopsy specimen was most consistent with ameloblastoma. The patient underwent right anterolateral maxillectomy including a rim of normal bone followed by placement of a palatal prosthetic splint over a split thickness skin graft. Seventeen months later he is doing well without evidence of recurrent disease. Bibliography Adekeye EO, Lavery KM: Recurrent ameloblastoma of the maxillofacial region. J Maxillofac Surg 14:153-7, 1986. Batsakis JG: Odontogenic lesions, in Tumors of the Head and Neck. Baltimore, Williams & Wilkens, 1979. Batsakis JG, McClatchey KD: Ameloblastoma of the maxilla and peripheral ameloblastomas. Ann Otol Rhinol Laryngol 92:532-3, 1983. Bredenkamp JK, Zimmerman MC, Mickel RA: Maxillary Ameloblastoma: A potentially lethal neoplasm. Arch Otolaryngol Head Neck Surg 115:99-104, 1989. Cannole PW: Tumors of dental origin: Ameloblastoma. Otolaryngol Clin North Am 12:141-4, 1979. Chow JI, Skolnik EM: Nonsquamous tumors of the oral cavity. Otolaryngol Clin North Am 19:573-607, 1986. Crawley WA, Levin LS: Treatment of ameloblastoma - a controversy. Cancer 42:357-63, 1978. Eliasson AH, Moser RJ, Tenholder MF: Diagnosis and treatment of metastatic ameloblastoma. South Med J 82:1165-8, 1989. Fitzgerald GWN et al: Ameloblastoma of the jaws: A 12 year review of the McGill experience. J Otolaryngol 11:23-8, 1982. Gardner DG, Pecak AMJ: The treatment of ameloblastoma based on pathologic and anatomic principles. Cancer 46:2514-19, 1980. Kahn MA: Ameloblastoma in young persons: A clinicopathologic analysis and etiologic investigation. Oral Surg Oral Med Oral Pathol 67:706-15, 1989. Kunza E et al: Biology of metastasizing ameloblastoma. Path Res Pract 180:526-35, 1985. Lanham RJ: Chemotherapy of metastatic ameloblastoma. Oncology 44:133-4, 1987. Laughlin, EH: Metastasizing ameloblastoma. Cancer 64:776-80, 1989. Lownie JF, Lurie R: Diagnosis and management of odontogenic tumors. Surg Annu 21:73-96, 1989. Marciani RD et al: Cryotherapy in the treatment of ameloblastoma of the mandible: report of cases. J Oral Surg 35:289-95, 1977. Pindborg JJ, Clausen F: Classification of odontogenic tumors. Acta Odont Scand 16:293-301, 1958. Regezi JA et al: Odontogenic tumors: Analysis of 706 cases. J Oral Surg 36:771-778, 1978. Richardson JF, Greer RO: Ameloblastoma of mucosal origin. Arch Otolaryngol 100:174-78, 1974. Robinson HBG: Ameloblastoma: A survey of 379 cases from the literature. Arch Pathol 23:831-43, 1937. Scaccia FJ, Strauss M, Arnold J, Maniglia AJ: Maxillary ameloblastoma: Case report. Am J Otolaryngol 12:20-25, 1991. Sehdev MK et al: Ameloblastoma of maxilla and mandible. Cancer 33:324-33, 1974. Simmons CC: Adamantinoma. Ann Surg 88:693-704, 1928. Slootweg MD, Muller H: Malignant ameloblastoma or ameloblastic carcinoma. Oral Surg 57:168-76, 1984. Small IA, Waldron CA: Ameloblastoma of the jaws. Oral Surg 8:281-97, 1955. Tsaknis PJ, Nelson JF: The maxillary ameloblastoma: An analysis of 24 cases. J Oral Surg 38:336-42, 1980. Grand Rounds Archive | Department Home page BCM Public | BCM Intranet | Privacy Notices | Contact BCM | BCM Site Map | ©2001-2006 Baylor College of Medicine
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