An Update on the Management of a Recurrent Ameloblastoma: A Case Report and Review of Literature.

Yan Trokel, BA; Robert Himmelfarb, DDS; William Schneider, MD, DDS; Robert Hou, MD DDS

Ameloblastoma is a common neoplasm affecting the jaws. It is an aggressive benign tumor of epithelial origin. Ameloblastoma's are infamous for their invasive growth and their tendency to recur. This is a case report of a recurrent ameloblastoma appearing bilaterally in the mandible. A short review of the different types, histology and management of these lesions are discussed.

INTRODUCTION

A meloblastoma is the most common neoplasm affecting the jaws, yet only accounts for 1% of all tumors of the maxilla and mandible and 11% of all odontogenic tumors.1 It is an aggressive benign tumor of epithelial origin which may arise from the enamel organ2, follicle, periodontal ligament3, lining of an odontogenic (dentigerous) cyst2,3 or the marrow of the jaws. Ameloblastomas are infamous for their invasive growth and their tendency to recur. This case report presents a study of a recurrent ameloblastoma with a review of the different types, histology and management of these lesions.

CASE REPORT

A 24 year old black male with a previous history of ameloblastoma presented with a chief complaint of anterior mandibular swelling. The patient had originally been diagnosed and treated at Queens Hospital Center on March, 1991. Initial biopsy revealed a multicystic ameloblastoma of the left mandible extending to the midline. His treatment in the operating room (under general anesthesia) consisted of enucleation, peripheral ostectomy, extraction of involved teeth and then placement of maxillomandibular fixation. The patient was lost to follow up.

Four years later the patient returned with a 5.0 cm bluish swelling of the anterior mandible with buccal and lingual bony expansion.

(figure 1) Photograph depicting a large (bluish) swelling in the anterior mandible

A panoramic radiograph demonstrated a multilocular lesion on the left side with an irregular outline extending from the mesial of the second premolar to the mid-line. The lesion extended superiorly from the alveolar ridge to one half the distance of the body of the mandible. There was marked resorption of the incisors. The right side revealed a unilocular, irregularly bordered lesion with few trabeculations approximating the inferior border of the mandible without expansion or thinning. of the mandible.

(figure 2)

Incisional biopsy of the lesion confirmed recurrent multicystic ameloblastoma. CT scan showed a destructive expansile lesion extending from the left mandibular body to the right mandibular body with anterior extension into the soft tissue. No gross evidence of lymphadenopathy was present.

The patient denied any significant past medical history and pre-operatory labs including CBC, PT/PTT, and UA were all within normal limits.

The patient was taken to the operating room for extensive curettage of the anterior mandible from the mid- body on the left side to the mid- body on the right side with the extraction of the involved teeth.

(figure 3)

Thereafter, a peripheral ostectomy was performed to a depth of approximately 5 mm. The patient was extubated and brought to the recovery room in stable condition.

DISCUSSION

The age range for ameloblastomas is from 20- 50 years5,6,7 with the average age being 27.18 There is no sex or racial predilection. Eighty percent of ameloblastomas occur in the mandible- almost exclusively in the molar ramus region of the mandible10,11,12 and are often associated with an unerupted teeth.13 The remaining twenty percent occur in the maxilla with the maxillary tuberosity being the most common site.2

Ameloblastomas are non-encapsulated tumors. Histologically there are two basic patterns, follicular and plexiform with the former being more common. In both patterns the stroma is composed of mature fibrous connective tissue; however, the follicular form contains islands of epithelial elements within the stroma and the plexiform contains cords of epithelial elements within the stroma.2

Ameloblastomas are classified into four groups; unicystic, solid or multicystic, peripheral, and malignant. The unicystic ameloblastoma is essentially a "cystic" lesion with either an intraluminal or an intramural proliferation of the cystic lining.9 Radiographically it is a well- circumscribed slow growing radiolucency. Microscopically, it is a "cystic" lesion with three significant features as described by Leider et al: (1) columnar cells resembling ameloblasts occupy the basal cell layer (2) hyperchromatic nuclei having a vacuolated atypical cytoplasm are polarized from the basal lamina and (3) a loose stellate reticulum- like epithelium lining the basilar ameloblasts.14 Unicystic ameloblastomas are less aggressive than solid ameloblastomas.9

The multicystic or solid ameloblastoma can grow to an enormous size. It can infiltrate into adjacent structures including intracranial sites, and has the ability to recur and even metastasize. It occurs in a slightly older age group than its unicystic counterpart. The majority of the cases involve the mandible, but the maxilla can also be involved. Radiographically, the appearance is variable with the exception of the desmoplastic variant, but it is generally unilocular or multilocular.15 Microscopically, this lesion can exhibit a variety of patterns. Multicystic ameloblastoma has a poorer prognosis than the cystic lesion.15

The peripheral ameloblastoma is the soft tissue version of the central intraosseous ameloblastoma. It occurs in the alveolar mucosa however,the underlying bone can be involved due to secondary erosion.16 This type of tumor is rare.

The malignant ameloblastoma is also a rare entity. Elzay and Corio et al. defined this lesion as an ameloblastoma that has metastasized but still maintains its classical microscopic features.17,18
Clinically, the majority of patients (75%) present with a chief complaint of a slow growing painless swelling. Signs and symptoms may include; facial deformity, swelling (75%), pain (33%), malocclusion, loosening of teeth, ill-fitting dentures and bridges, ulcerations and periodontal disease.8

Radiology and location of ameloblastomas are key factors to a correct diagnosis. Plain radiography, panoramic radiographs, conventional tomography (CT's), and magnetic resonance imaging(MRI's) are all used as diagnostic aids. Findings may include expansion of cortical plate with scalloped margins, multiloculations or "soap bubble" appearance, and/or root resorption. CT's are used to delineate soft tissue masses, destruction of cortical bone and extension of the tumor into adjacent structures. MRI's, even though not useful for hard tissue examination, are used to provide information regarding edge definition and tumor consistency.19

Ameloblastoma is a locally benign invasive tumor that has a high tendency to recur, metastasize and even undergo malignant transformation. It has a high recurrence rate if not adequately removed,4 but local recurrence may occur even in patients who have undergone satisfactory primary surgical treatment.1 As these tumors recur they become more aggressive and can develop into a lesion that is more aggressive than a sarcoma.8 Recurrence seems to depend on several factors such as; (1) method of treatment of the primary lesion, (2) the extent of the lesion, and (3) the site of origin.23

Among the various types of ameloblastomas there are differences in recurrent patterns. Multicystic ameloblastoma has a much higher rate of recurrence than unicystic ameloblastoma. The reason for this higher rate is believed to be because of the numerous micro-extensions the tumor has projecting into the bone.24,25 Gardner and Pecak stress that the type of treatment required is highly dependent on the type of ameloblastoma present.4

Recurrence rates also vary for the different procedures used to treat the primary lesion.Several authors have found a recurrence rate of 55 to 90 percent for all ameloblastomas treated conservatively (enucleation and curettage).11 However, the incidence of recurrence following radical resection is 5 to 15 percent.23,24

Surgery is the mainstay of therapy for ameloblastomas today. Treatment ranges from conservative surgery to more radical procedures. Conservative therapy includes radiotherapy, curettage, and enucleation. Radical surgery as defined by Muller and Slootweg is a procedure in which the ameloblastoma is removed with a margin of "normal bone."10 Most investigators believe in resecting at least 1 cm. of normal bone beyond the tumor margin.4,20 Soft tissue borders at the time of resection may also be confirmed by frozen sections to ensure complete tumor removal.15

An ameloblastoma is an epithelial tumor similar to a basal cell carcinoma histologically. Therefore, some investigators contend that their radiosensitivities must also be similar.21 However, radiation therapy is rarely used as a primary treatment. Gardner believes that radiotherapy should only be used for inoperable cases.8 Other investigators advocate that radiotherapy in conjunction with surgery may have a place in the management of selected patients with recurrence. Pinsolle et al. believe that surgery and radiotherapy (50 Gy postoperatively) should be used for (1) mandibular recurrences when the first surgical treatment was adequate, (2) for all recurrences and (3) when soft tissue involvement or positive surgical margins are present after a wide resection.21

CONCLUSION

This case report illustrates the importance of adequate radical resection to avoid recurrence. All efforts must be made to excise the recurrent lesion because death can occur as a result of damage to vital structures by massive local disease and metastasis. Recurrences often present after fifteen years or more.4 Therefore, it is important to emphasize the need for long term periodic follow ups.

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