Peripheral ameloblastoma of the buccal mucosa: Case report and review of the English literature

Peripheral ameloblastoma of the buccal mucosa: Case report and review of the English literature

Peripheral ameloblastoma of the buccal mucosa: Case report and review of the English literature Sook-Bin Woo, B.D.S., M.S.,* Jennifer E. Smith-William...

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Peripheral ameloblastoma of the buccal mucosa: Case report and review of the English literature Sook-Bin Woo, B.D.S., M.S.,* Jennifer E. Smith-Williams, D.M.D.,** James J. Sciubba, D.M.D., Ph.D.,*** and Stanley Lipper, M.B., Ch.B.,**** Long Island and New Hyde Park, N.Y. LONG









An unusual case is presented of a peripheral ameloblastoma arising on the buccal mucosa, which brings the total number of such cases to three. The occurrence and pathogenesis of peripheral ameloblastomas in general, are reviewed, especially with reference to the basal cell carcinoma. (ORAL SURG. ORAL MED. ORAL PATHOL. 1987;63:78-84)


he ameloblastoma is a neoplasm of odontogenic epithelium, specifically of enamel organ-type tissue that has not undergone differentiation to the point of hard tissue formation. It generally occurs in bone, and it has been postulated that the epithelium of origin is derived from one of the following sources: (1) the developing enamel organ, (2) cell rests of the enamel organ, (3) epithelium of odontogenic cysts, (4) basal cells of the surface epithelium, or (5) heterotopic epithelium, as in lesions that occur at extraoral sites.’ The peripheral ameloblastoma is histologically indistinguishable from the typical central or intraosseousameloblastoma but is different in that it occurs in the soft tissue overlying alveolar bone but separate from it. An origin from either surface epithelium or remnants of the dental lamina is favored.’ Two cases25 3 of peripheral ameloblastoma have been reported on the buccal mucosa (Table I). This is a report of a third case of a peripheral ameloblastoma arising in the buccal mucosa. CASE REPORT

A 52-year-old Guyanese woman of East Indian origin was referred to the Oral and Maxillofacial Surgery Clinic at Queens Hospital Center for the evaluation of an ulcerated lesion of the right buccal mucosa. Approximately 9 months before her visit, the patient noticed a massin this

region. She thought that it was an abscess and that it would eventually drain and heal. The lesion was brought to medical attention as a result of its interfering with mastication and because the patient’s friends and relatives noticed the persistent right facial swelling. Her past medical history was positive for hypertension, chronic heart failure, and osteoarthritis. Her medications were hydrochlorothiazide, digoxin, potassium chloride, and aspirin. The patient stated that she had an allergy to methyldopa (Aldomet). Clinical examination

Clinical examination revealed an East Indian woman, who looked her stated age and was in no apparent distress. She had moderate right facial swelling but no facial paralysis, paresthesia, or anesthesia and no palpable regional lymphadenopathy. The right parotid gland was not enlarged or tender. On extraoral palpation, a firm, freely movable masscould be felt, measuring approximately 3.0 cm in diameter. It appearedmedial to the buccinator muscle. On intraoral examination, an ulcerated, somewhat friable exophytic mass was seen (Fig. 1). Its anterior extent was immediately posterior and inferior to the orifice of Stensen’s duct, from which there was unimpeded clear salivary flow. The lesion did not extend to the maxillary or mandibular alveolar ridge. The ulcerated area coincided with the occlusal line when her dentures were inserted. A panoramic radiograph did not demonstrate a direct relationship to bone. Management

*Fellow, Department of Pathology. **Chief Resident, Division of Oral and Maxillofacial Surgery. ***Chairman, Department of Dentistry. ****Director, Department of Laboratories, Queens Hospital Center.


An incisional biopsy was performed through the ulcerated portion of the mass, at which time it was noted as indurated with a papillary surface. The submitted tissue was reported to be “consistent with a peripheral ameloblas-

Peripheral ameloblastoma of buccal mucosa 79

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I. Cases of peripheral ameloblastoma not on attached mucosa Age, sex, race



63 yr, male,white



yr, male, Oriental

52 yr. female, East Indian

Present case ‘FOD

1. Intraoral photograph of mass in right buccal mucosa.

Location1 appearance

Left buccal mucosa/firm, painlessmass Right buccal mucosa, medial to ramus/ulcerated and indurated Right buccal mucosa/ulcerated firm, papillary mass

Size (cm)

Continuity with basal layer









mo FOD*

Excisedwith wide


mo FOD


mo FOD




Locally excised

= free of disease

toma.” Based on this diagnosis the lesion was removed via an intraoral approach while the patient was under general anesthesia. The mass was dissected free with relative ease from the buccinator muscle. A fibrous capsule separated the massfrom the surrounding tissue, and the parotid duct was excised at its point of entry into the lesion. The proximal portion of the duct was sutured beneath the original orifice to Stensen’s duct. The patient tolerated the procedure well. Nine months after surgery there was minimal trismus, normal function of the right parotid gland, and no sign of clinical recurrence of the lesion. Pathology


The fresh specimen measured 3.0 X 2.5 X 1.5 cm and, on cut section, consisted of a thinly encapsulated, multilobulated, white, firm mass (Fig. 2). The overlying mucosa was ulcerated, and small papillary projections protruded into the ulcer. Histologic examination revealed a proliferation of epithelium in anastomosing cords, strands, and

solid sheets.The peripheral cells were palisaded with their nuclei polarized away from the basement membrane; these cells delineated stellate reticulum-like areas with occasional spindled cells and acanthomatous areas (Figs. 3 and 4). In addition, strands and clusters of cells, reminiscent of odontogenic epithelial rests, streamed from the main mass (Figs. 4 and 5). This showed continuity with the overlying papillary surface epithelium. The basementmembrane was focally hyalinized and was positive with periodic acidSchiff (PAS). The epithelial cells did not stain with PAS, mucicarmine, or Alcian green stains. Material for electron microscopy was obtained after fixation in formalin and as such, was of poor diagnostic quality. It confirmed reverse polarization of the nuclei in the peripheral cells with lateral desmosomesand hemidesmosomesattached to the basal lamina. Intermediate dark cells were sandwiched between the columnar cells. Bundles of tonofilaments lay free in the cytoplasm, and some were inserted into junctional complexes. Outlines of mitochondria and other organelles were seen.The stellate reticulum

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Fig. 2. Whole-mount section showing lobulated configuration and continuity with surface epithelium. (Hematoxylin and eosin stain. Magnification, ~7.)

Fig. 3. Photomicrograph showing fibrous capsule on left and plexiform arrangement of cells. (Hematoxylin and eosin stain. Magnification, x45.)

cells were polyhedral, had desmosomal attachments, and tonofilaments, and were markedly degenerated. DISCUSSION

Stanley and Krogh4 were the first to adequately document a case of ameloblastoma that was located entirely within soft tissue overlying bone but separate from it. Since then, many other such caseshave been reported,5-19most commonly designated peripheral ameloblastoma but also known as muco.sal,5extramedullary,” extraosseous,” and soft tissueI ameloblastomas. Cases of basal cell carcinomas arising from the

oral mucosa have also been reported.20-25Some authors’3z24’26 consider the peripheral ameloblastoma and the oral basal cell carcinoma as the same lesion, whereas others16~‘8 believe that there are histologic features that separate the two lesions. For the ensuing discussion, we have adopted the opinion that the two lesions are essentially the same. A summary of the clinical features of the twentythree previously reported casesof peripheral ameloblastomas occurring on mucosa overlying bone is presented in Table II. Only a few salient points will be mentioned. The peripheral ameloblastoma is a lesion of adult-

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of buccal mucosa


Fig. 4. Photomicrograph showing reverse polarization of basal cells delimiting stellate reticulum-like areas. (Hematoxylin and eosin stain. Magnification, ~225.)

Fig. 5. Photomicrograph showing strands of epithelium reminiscent of odontogenic “rest.” (Hematoxylin and eosin stain. Magnification, X 112.)

hood with approximately 52% of patients ranging from 40 to 60 years of age. Of the twenty-three patients, thirteen were men and ten were women; thirteen lesions occurred in the mandible and ten in the maxilla. However, seven out of ten cases of lesions in the maxilla occurred in the posterior maxilla and/or tuberosity area; casesof mandibular lesions were more evenly distributed. Radiographic findings were usually negative, although in some cases, saucerization of the underlying bone was evident. Fourteen out of eighteen cases (77.8%) showed continuity of the neoplasm with the overlying

epithelium. Of the eighteen casesthat had follow-up information, four cases had recurrences within 2 months,5 9 months,2118 months,7 and 8 years.z5One case involved a recurrent lesion noted 5 years after initial treatment.lg The recurrences were all in the group treated by excision of the lesion. Other modalities of treatment


en bloc resections,6* *O

curettage,4 and cryosurgery plus radiation.25 The case reported here is similar to those cases reported by BraunsteinZ and Klinar and McManis.3 All three cases involved middle-aged patients who had 3 to 5 cm painless massesin the buccal mucosa.


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II. Analysis of 23 caseswith published data

Age 23-92 yr Median age of 58 yr Average age of 52.7 yr 12/23 (52.1%) were 40-60 yr of age Sex 13 men 10 women Race 15 whites 2 Indians 1 black 5 unstated Location 13 mandible, 4 anterior, 4 midportion, 5 posterior 10 maxilla, 7/10 in posterior/tuberosity Size 0.3-4.0 cm 21 caseswere less than 2.0 cm 1 case was 4.0 cm Continuity with basal layer 14/ 18 had continuity 4/18 had no continuity 5 casesunstated Treatment 19/23 excisions 2 en bloc resections 1 curettage 1 cryosurgery and radiation Follow-up 5 months to 8 years 4 cases recurred within 2 months, 9 months, 18 months, and 8 years 1 case when first seen was a recurrence 5 years after initial treatment Recurrence rate, 5/19 (26.3%)

Although BraunsteirC described his case as an adamantino blastoma-a malignant tumor with bizarre-shaped nests of cells-the description of the nests and the photomicrographs support a diagnosis of ameloblastoma, The papillary features of this case have been seen in other peripheral ameloblastomas.7.9,16,17.21 Saint27 described a case of basal cell carcinoma arising on the dqrsum of the tongue, but neither the clinical findings nor the histology were well documented. Thoma and Goldma+ reported a case that involved a 62-year-old man who had squamous cell carcinoma of the floor of the mouth, associated with a basal cell carcinoma of the adjacent alveolus, which according to Gardner” and Lawson and colleagues,21represented an intraosseous ameloblastoma. The radiographic picture was not discussed, but from the clinical desciiptions and photograph, the alveolar lesion expanded both buccal and lingual aspects of the mandible, making it an unlikely

candidate for a peripheral ameloblastoma and/or basal cell carcinoma. The two casesof basal cell carcinoma arising from the mucosal surface of the lower lip, reported by Keen and Elzay29and Weitzner and Hente130may be an expression of the multicentricity of the growth pattern of basal cell carcinomas of the skin, since these two patients simultaneously had basal cell carcinoma of the upper lip29and the adjacent skin,30 respectively, and also had previous histories of basal cell carcinoma elsewhere on the body. Of the seven casesof basal cell carcinoma arising on the attached mucosa,20-25 three cases20y21,23 had a history of basal cell carcinoma on other parts of the body. This may have influenced the respective authors to diagnose the oral lesions as basal cell carcinoma, since the simultaneous or subsequent occurrence of several lesions of basal cell carcinoma is not an infrequent finding.31 Some authors’6sI8 believe that a distinction can be drawn between the histologic features of the basal cell carcinoma and the peripheral ameloblastoma. Greer and HammondI believe that the peripheral ameloblastoma exhibits central polarization of the nuclei of the peripheral cells and that the true intraoral basal cell carcinoma shows a sharp demarcation between the peripheral cells and the central reticular cells. Patrikiou and colleagues1Ebelieve that a diagnosis of basal cell carcinoma should be made for lesions continuous with the surface epithelium, and a diagnosis of ameloblastoma should be made if it is separated from the surface by fibrous connective tissue and shows the histology of “typical ameloblastoma.” The ultrastructural findings of this caseand previously reported casesI 32are rather nonspecific. They merely confirm the epithelial nature of the lesion. In contrast, the intraosseous follicular ameloblastoma has the characteristics of an actively secreting cell: dilated endoplasmic reticulum; large, infranuclear Golgi apparatus and accumulation of dense-core secretory granules and coated vesicles in the basal cytoplasm of the peripheral cells.33Perhaps this is in accord with the more aggressivenature of the central lesions (Table III), which tend to have a higher recurrence rate34 (bearing in mind these are 1972 figures). The oral mucosa can be thought of as an extension of the skin. Just as there are skin appendages, so there are teeth. Lever and Schaumburg-Lever3’ believe that the basal cell carcinoma, the least 4iFerentiated of the skin appendage neoplasms, arises from the pluripotent cells that form continuously during life and have the potential to form hair


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of buccal mucosa


III. Central versus peripheral ameloblastoma Peripheral

Central (128 cases)34 Age Mean 31 yr 66.7% less than 40 yr Location Mandible: maxilla = 3.5:1 78% mandible Radiographic picture Unitocular or multilocular radiolucency Continuity with basal layer Occasionally seen if it erodes through bone Recurrence 45.7% after primary treatment 6 I. 1% after secondary treatment

(23 cases)

Mean 52.1 yr 52% 40 to 60 yr Mandible: maxilla = 13:lO 56.6% mandible Negative radiographic

findings except for occasional saucerization

77.8%, 14/18 cases had continuity 26.3% overall

and sebaceousand apocrine structures. The ameloblastoma, the least differentiated of the epithelial odontogenic neoplasms, can conceptually arise from similar pluripotent cells of the basal layer of oral epithelium or their derivatives, namely, dental lamina rests (glands of Serres). These epithelial vestiges of odontogenesis can usually be found within the maxilla and mandible near teeth, are associatedwith developmental cysts, and can be found also in soft tissue overlying the tooth-bearing areas of the jaws. In this location, they are the suggested origin for a host of developmental odontogenic cysts and neoplasms. Therefore, it is not surprising that peripheral ameloblastomas and/or basal cell carcinomas of the oral cavity arise on mucosa overlying the alveolar processes. However, it is difficult to explain the origin of a peripheral ameloblastoma that arises in the buccal mucosa on the basis of dental lamina rest proliferation, since such rests must occur rarely in such a location. This may explain the extremely rare incidence of peripheral ameloblastoma in the buccal mucosa. Another possibility lies in the rests being not so much of dental lamina origin as remnants of the vestibular lamina, which is involved in the formation of the buccal sulcus and mucosa. Although the presenceof ectopic glands of Serres cannot be ruled out, a more likely explanation is origin from pluripotent cells in the basal cell layer of the mucosal epithelium. Although dental lamina rests have been putatively implicated in the formation of a variety of odontogenie neoplasms, the natural history and kinetics of these rests remain poorly understood. If they are end-stage cells with a limited life span, one would expect that they would ultimately disappear. The fact that many cysts and neoplasms, including the

peripheral ameloblastoma, occur in middle age or later does not support this notion. The second possibility is that they are self-replenishing units with their own population of pluripotent cells. Much more work still needsto be done before one can understand how these rests can actually be appropriately stimulated to proliferate. The differential diagnosis of this lesion includes the odontogenic gingival epithelial hamartoma,35the peripheral odontogenic fibroma,36*37and a salivary gland neoplasm.38.39Pindborg and Kramer36 and Shafer and co-workers3’ believe the first two are related lesions. They are predominantly mesenchyma1 processeswith abundant fibrous elements and various amounts of calcified material and odontogenic epithelium. Where the epithelial component is exuberant, perhaps they can be mistaken by a pure epithelial neoplasm like the peripheral ameloblastoma. Moskow and Baden” suggested that basal cell carcinomas on the lips, tongue, and buccal mucosa may also represent the adamantinoid variant of squamouscell carcinoma but did not elaborate on the point. Foote and Frazel138described one case of a pseudoadamantine adenocarcinoma of the salivary glands. This would be a malignant neoplasm, however, and the features of the casereported here support a benign diagnosis. The basal cell adenoma may resemble the ameloblastoma.39However; in this case the presence of stellate reticulum-like areas and the streaming strands of epithelium with .palisaded peripheral cells and polarized nuclei favor the diagnosis of an ameloblastoma. Histochemical stains have not been helpful in differentiating between the two. Stains for epithelial mucin were positive in the one case of a membranous basal cell adenoma reported by Headington and co11eagues,4o whereas


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Oral Surg. January. 1387

Christ and Crocker4’ felt that the staining reactions for this group of salivary gland tumors were neither characteristic nor diagnostic. CONCLUSION

This is the third case of a peripheral ameloblastoma arising in the buccal mucosa that has been reported in the English-language literature. Whether these lesions should be separated from the peripheral ameloblastomas of the attached soft tissues and be called basal cell carcinomas is a matter of semantics. The origin of both lesions in the oral cavity is either from the pluripotent cells of the basal cell layer or from native or ectopic epithelial rests. Becausedental lamina rests must occur infrequently in the buccal mucosa, if at all, it is likely that a peripheral ameloblastoma arising in this location would most probably originate from pluripotent cells in the overlying basal layer. Complete local excision is the treatment of choice. Although the innocuous nature of this lesion has been stressed, on reviewing nineteen cases with follow-up information, the recurrence rate is 26%. Patients should be kept under periodic observation becauseof reports of recurrences even up to 8 years after initial treatment. REFERENCES 1. Shafer WG: Hine MK, Levy BM: A textbook of oral pathology, ed. 4, Philadelphia, 1983, W. B. Saunders Co., pp. 276-285. 2. Braunstein E: Case report of an extraosseous adamantinoblastoma. ORAL SURG ORAL MED ORAL PATHOL 2726-728, 1949. 3. Klinar KL, McManis JC: Soft tissue ameloblastoma. ORAL. SURG ORAL MED ORAL PATHOL 28:266-272,


4. Stanley HRJ, Krogh HW: Peripheral ameJoblastoma. Report of a case. ORAL SURG ORAL MED ORAL PATHOL 12~760-765, 1959. 5. Russell A: Ameloblastoma of mucosal origin: NZ Dent J 62:116-118, 1966. 6. Lee KW, Chin TC, Paul G: Peripheral ameloblastoma. Br J Oral Surg 8:150-153, 1970. I. Wertheimer FW, Stroud DE: Peripheral ameloblastoma in a papilloma with recurrence. J Oral Surg 30:47-49, 1972. 8. Wallen NG: Extraosseous ameloblastoma. ORAL SURG ORAL MED ORAL PATHOL 34~95-97,


9. Balfour RS, Loscalzo LJ, Sulka M: Multicentric peripheral ameloblastoma. J Oral Surg 31:535-538, 1973. IO. Richardson JF, Greer RO: Ameloblastoma of mucosal origin. Arch Otolaryngol 100:174-175, 1974. I I. Pansino FA, Meara JW, Jr: Case report: Peripheral ameloblastoma. J Mich State Dent Assoc 57:129-130, 1975. 12. Wesley RK, Borninski ER, Hintz S: Peripheral ameloblastoma: Report of a case and review of the literature. J Oral Surg 35~670-672, 1977. 13. Gardner D: Peripheral ameloblastoma. Cancer 391625-1633, 1977. 14. Frankel K, Smith JD, Frankel L: Soft tissue amelobiastoma in a 92-year-old woman. Arch Otolaryngol 103:499-501, 1977. 15. Birkholz H, Sills AH, Reid R: Peripheral ameloblastoma. J Am Dent Assoc 97:658-660, 1978.

16. Greer RO, Hammond SW: Extraosseous ameloblastoma Light microscopic and ultrastructural observation<. .I Oral Surg 36:553-556, 1978. 17. Moskow BS, Baden E: The peripheral ameloblastom;~ 01‘ rile gingiva. J Periodontol 53736-742, 1982. 18 Patrikiou A, Papanicolaou S, Stulogianni E, Sotiriadou S: Peripheral ameloblastoma. Int J Oral Surg 12:51-5.5. 1983 19. Curalnick W, Chuong R, Goodman M: Peripheral ameloblastoma of the gingiva. J Oral Maxillofac Surg 41:536-539, 1983. 20. Williamson JJ, Cohney BC, Henderson BM: Basal ccl1 carcinoma of the mandibular gingiva. Arch Dermatol 95:7680. 1967. 21. Lawson BF, Griffin JW, Waldron CA: Basal cell carcinoma of the gingiva. ORAL SL’KG ORAI MED ORAL PATHOI 24:64X653, 1967. 22. Peters RA, Gingrass RP. Keyes CN, Katz CS: Basal cell carcinoma of the oral cavity. J Oral Surg 30:63-66, 1972. 23. Liroff KP, Seymour Z: Basal cell carcinoma of the palatal mucosa. J Oral Surg 30:730-733, 1972. 24. Simpson HE: Basal cell carcinoma and peripheral ameloblastoma. OKAI SURG ORAL MED ORAL. PATtiOL 38:233-240. 1974. 25. Samit AM: Intraoral basal cell carcinoma. J Surg Oncol 10:27-32, 1978. 26. Waldron CA: Comment on Peters RA, Gingrass RP, Reyes CN, and Hintz CS: Basal cell carcinoma of the oral cavity. J Oral Surg 30:66, 1972. 27. Saint CFM: The embryology of the stomodeum and its bearing on the pathology of tumours of the tongue and the salivary glands. S Afr J Clin Sci 21-17, 1951. 28. Thoma KH, Goldman HM: Oral pathology, ed. 5, St. Louis, 1960. The C. V. Mosby Company, pp. 1441-1442. RP: Basal cell carcinoma from mucosal 29. Keen RT, hay surface of lower lip. J Oral Surg 22:453-455. 1964. 30. Weitzner S, Hentel W: Multicentric basal-cell carcinoma of vermilion mucosa and skin of lower lip. ORAL SURG ORAL MFD ORAL PATHOL 26~269-272,


31. Lever WF, Schaumburg-Lever G: Histopathology of the skin, ed. 6, Philadelphia, 1983, J. B. Lippincott Co., pp. 572-573. 32. Gould AR, Farman AG, DeJean EK, Van Arsdall 1-R: Peripheral ameloblastoma. J Oral Pathol 11:90- 101, 1982. 33. Cutler LS, Innes DJ, Jr: An electron microscopic and cytochemical study of follicular ameloblastoma. J Oral Path01 12:x%514, 19x3. 34. Mehlisch DR, Dahlin DC, Masson JK: Ameloblastoma: A clinicopathologic report. J Oral Surg 30:9, 1972. 35. Baden E, Moskow BS, Moskow R: Odontogenic gingival epithelial hamartoma. J Oral Surg 26:702-714, 1968. 36. Pindborg JJ, Kramer IR: Histological typing of odontogenic tumours. jaw cysts and allied lesions. Geneva, 1971, World Health Organization. 31. Shafer WG, Hine MK, Levy BM: A textbook of oral pathology. Philadelphia, 1983, W. B. Saunders Co., pp. 292-294. 38. F’oote FW, Frazell EL: Tumors of minor salivary glands. Cancer 631065-I 133, 1953. 39. Batsakis JG: Tumors of the head and neck, ed. 2, Baltimore. 1979. Williams & Wilkins, pp. 50-53. 40. Headington JT, Batsakis JG, Beals TF, Campbell TE, Simmons JL. Stone WD: Membranous basal cell adenoma of parotid gland, dermal cylindromas and trichoepithelioma. Cancer 392460-2469, 1971. 41. Christ TF, Cracker D: Basal cell adenoma of minor salivary gland origin. Cancer 30:214-219. 1972. Reprint



Dr. Sook-Bin Woo Department of Oral Pathology Harvard School of Dental Medicine I88 Longwood Ave. Boston, Massachusetts