Odontogenic Tumors

1. Odontogenic Tumors

8. Classification of Odontogenic Tumors* • I. Tumors of odontogenic epithelium • A. Ameloblastoma 1. Malignant ameloblastoma 2. Ameloblastic carcinoma • B. Clear cell odontogenic carcinoma • C. Adenomatoid odontogenic tumor • D. Calcifying epithelial odontogenic tumor • E. Squamous odontogenic tumor • II. Mixed odontogenic tumors • A. Ameloblastic fibroma • B. Ameloblastic fibro-odontoma • C. Ameloblastic fibrosarcoma • D. Odontoameloblastoma • E. Compound odontoma • F. Complex odontoma • III. Tumors of odontogenic ectomesenchyme • A. Odontogenic fibroma • B. Granular cell odontogenic tumor • C. Odontogenic myxoma • D. Cementoblastoma • * From Neville, et al.

9. Biologic Classification of Odontogenic Tumors* • BENIGN, AGGRESSIVE • Ameloblastoma • Clear cell odontogenic tumor (some consider this a carcinoma) • Odontogenic ghost cell tumor (COC, solid type) • Odontogenic myxoma • Odontoameloblastoma • MALIGNANT • Malignant ameloblastoma • Ameloblastic carcinoma • Primary intraosseous carcinoma • Odontogenic ghost cell carcinoma • Ameloblastic fibrosarcoma • BENIGN, NO RECURRENCE POTENTIAL • Adenomatoid odontogenic tumor • Squamous odontogenic tumor • Cementoblastoma • Periapical cementoosseous dysplasia • Odontoma • BENIGN, SOME RECURRENCE POTENTIAL • Cystic ameloblastoma (unicystic) • Calcifying epithelial odontogenic tumor • Central odontogenic fibroma • Florid cementoosseous dysplasia • Ameloblastic fibroma and fibroodontoma • *From Regezi, et al.

10. Tumors of Odontogenic Epithelium

11. Ameloblastoma • The ameloblastoma is the most common clinically significant (not the most common) odontogenic tumor. • It may develop from cell rests of the enamel organ; from the developing enamel organ; from the lining of odontogenic cysts or from the basal cells of the oral mucosa.

12. Ameloblastoma • It is typically slow-growing, locally invasive and runs a benign course. • H.G.B. Robinson described it as being a benign tumor that is “usually unicentric, non-functional, intermittent in growth, anatomically benign and clinically persistent.”

13. Ameloblastoma • Ameloblastomas occur in 3 different clinico-radiographic situations requiring different therapeutic considerations and having different prognoses. • Conventional Solid/Multicystic (86 % of all cases) • Unicystic (13 % of all cases) • Peripheral or Extraosseous (1 % of all cases)

14. Solid or Multicystic Ameloblastoma: Clinical Features • Patient Age: Approximately equal frequency from the third through the seventh decades. • Sex Predilection: Approximately equal. • Location: 80 % in mandible; 70 % in posterior regions. • Radiographic Appearance: Radiolucent lesion which is usually well-circumscribed; it may be unilocular or multilocular (soap-bubble, honeycomb); occasionally an ameloblastoma will be ill-defined with a ragged border.

15. Solid or Multicystic Ameloblastoma: Histologic Features • There are several microscopic subtypes but these generally have little bearing on the behavior of the tumor. • The follicular and plexiform types are the most common. • The follicular type is composed of islands of epithelium which resemble the enamel organ in a mature fibrous connective tissue stoma.

16. Solid or Multicystic Ameloblastoma: Histologic Features • The plexiform type is composed of long, anastomosing cords or larger sheets of odontogenic epithelium. Its stroma tends to be loose and more vascular. • The acanthomatous type shows evidence of extensive squamous metaplasia with keratin formation in the island of odontogenic epithelium.

17. Solid or Multicystic Ameloblastoma: Histologic Features • In the granular cell type there is transformation of groups of epithelial cells to granular cells; the nature of the granular change is unknown. This type is more common in young patients and has been shown to be clinically aggressive.

18. Solid or Multicystic Ameloblastoma: Histologic Features • The desmoplastic form is composed of islands/cords of odontogenic epithelium in a very dense collagenous stroma. It has a predilection for the anterior maxilla and because of the dense connective tissue may appear as a radiolucent-radiopaque lesion. • The basaloid type is the least common and is composed of uniform basaloid cells with no stellate reticulum.

19. Solid or Multicystic Ameloblastoma: Additional Features • In some studies solid/multicystic ameloblastomas are reported to be more common in Blacks. • While lesions are generally asymptomatic, ameloblastomas may cause paresthesia, pain particularly if infected and they can erode the cortical palates.

20. Solid or Multicystic Ameloblastoma: Treatment • Treatments have ranged from simple enucleation and curettage to en bloc resection. • Marginal resection is the most widely used method of treatment with the least recurrences reported (up to 15 %). • Most surgeons advocate a margin of at least 1.0 cm beyond the radiographic limits of the tumor as the tumor often extends beyond the apparent radiologic/clinical margins.

21. Solid or Multicystic Ameloblastoma: Prognosis • Treatment with curettage has resulted in recurrence rates ranging from 55-90 %. • Treatment with marginal resection has resulted in approximately a 15 % recurrence rate. • Ameloblastomas of this type arising in the maxilla are particularly dangerous as it is often difficult in getting adequate margins. • Rarely is an ameloblastoma life threatening.

37. Unicystic Ameloblastoma: Clinical Features • Patient Age: The patients are younger than those with the solid/multicystic form. 50% are diagnosed during the second decade of life. • Sex Predilection: ? Same as for the solid?? • Location: 90 % occur in the mandible usually in the posterior region. • Radiographic Appearance: Typically appears as a RL around the crown of an unerupted tooth (most commonly a mandibular third molar).

38. Unicystic Ameloblastoma: Histologic Features • Three histopathologic variants are recognized: • Luminal: the tumor is confined to the luminal surface of the cyst. • Intraluminal/plexiform: the tumor projects from the cystic lining; sometimes resembles the plexiform type of solid/multicystic ameloblastoma. • Mural: the tumor infiltrates the fibrous cystic wall.

39. Unicystic Ameloblastoma: Treatment and Prognosis • Enucleation of the cyst is probably adequate for the luminal and intraluminal/plexiform types. • Treatment of the mural type is controversial with some surgeons believing that local resection is best. • 10-20 % recurrence after enucleation and curettage with all unicystic ameloblastomas.

45. Peripheral Ameloblastoma • These tumors are extraosseous and therefore occupy the lamina propria underneath the surface epithelium but outside of the bone. • Histologically, these lesions have the same features as the intraosseous forms of the tumor.

46. Peripheral Ameloblastoma: Clinical Features • Patient Age: Wide age range but most occur during middle-age. • Gender Predilection: This is not known. • Location: Posterior gingival/alveolar mucosa is involved most frequently. There is a slight predilection for the mandible. The buccal mucosa has been the site in a few reported cases.

47. Peripheral Ameloblastoma: Radiographic & Histologic Features • Radiographic Appearance: Although not in bone, a few cases have shown superficial erosion of the alvelolar bone. • Histologic Appearance: Islands of ameloblastic epithelium are observed in the lamina propria; plexiform and follicular patterns are the most common; in 50 % of the cases the tumor connects with the basal cell layer of the surface epithelium.

48. Peripheral Ameloblastoma: Treatment and Prognosis • Unlike its intraosseous counterpart, this tumor has an innocuous clinical behavior. • Patients respond well to local surgical excision. • Some reports indicate a 25 % recurrence rate but in these cases as second surgical procedure results in cure. • There has been a rare malignant change reported.

50. Malignant Ameloblastoma and Ameloblastic Carcinoma • Less than 1 % of the ameloblastomas show malignant behavior with the development of metastases. • Malignant ameloblastoma is a tumor that shows histologic features of the typical (benign) ameloblastoma in both the primary and secondary deposits. • Ameloblastic carcinoma is a tumor that shows cytologic features of malignancy in the primary tumor, in recurrence and any metastases.