A peripheral ameloblastoma arising on the buccal mucosa is exceedingly rare. Only three document cases have been reported, and we present one additional case of this tumor. In this case, the lesion repeatedly occurred in the same location in spite of twice local excisions. The first lesion was diagnosed as basal cell carcinoma with ameloblastomatous features. The pathological findings of the lesion were palisading of the peripheral cells of epithelial masses and structures resembling stellate reticulum, which could also be observed also in peripheral ameloblastomas. The second lesion was diagnosed as basal cell adenoma, and the third as peripheral ameloblastoma. The histogenesis of peripheral ameloblastomas and intraoral basal cell carcinomas are discussed, especially with reference to the lesions of the buccal mucosa

Akamine Katsuji

Hamada Yushi

Hokama Seitetsu

Kiyuna Masaya

Shinzato Takashi

Toda Takayoshi

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Acta Med. Nagasaki 35:189-193PERIPHERAL AMELOBLASTOMA OF THE  BUCCAL MUCOSA : WITH A REVIEW        OF THE LITERATURETakashi SHINZATO 1, Takayoshi TODA 1, Masaya KIYUNA 1 Yushi HAMADA 1, Seitetsu HOKAMA 1 and Katsuji AKAMINE 2Department of Clinical Laboratory and Laboratory Medicine 1 and Department of Otolaryngology 2, School of Medicine, University of the Ryukyus, Okinawa, JapanReceived for publication, June 25, 1990SUMMARY : A peripheral ameloblastoma arising on the buccal mucosa is exceedingly rare. Only three document cases have been reported, and we present one additional case of this tumor. In this case, the lesion repeatedly occurred in the same location in spite of twice local excisions. The first lesion was diagnosed as basal cell carcinoma with ameloblastomatous features. The pathological findings of the lesion were palisading of the peripheral cells of epithelial masses and structures resembling stellate reticulum, which could also be observed also in peripheral ameloblastomas. The second lesion was diagnosed as basal cell adenoma, and the third as peripheral ameloblastoma. The histogenesis of peripheral ameloblastomas and intraoral basal cell carcinomas are discussed, especially with reference to the lesions of the buccal mucosa.       INTRODUCTION  Ameloblastoma is a odontogenic neoplasm that most often occurs in bone, and its origin has been accepted to be 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 thr surface epithelium, or (5) heterotopic epithelium, as in lesions that occur at extraoral sites (10).  The histogenesis of the peripheral amelobla-stoma is controversial. The peripheral ame-loblastoma is described as a neoplasm arising in soft tissue overlying tooth bearing region, not including the buccal mucosa, the lips, the craniopharyngeal duct, or the tibia (1). On the other hand, Shiba emphasized (12) that ameloblastomas arising in buccal mucosa orlabial mucosa should come within the same category of peripheral ameloblastoma, and indeed three cases of ameloblastoma arising in the buccal mucosa has been described (2, 7, 13). And it is generally accepted that peripheral ameloblastoma arises from the basal cells of the oral mucosa of from remnants of the dental lamina (3).  We herein report a fourth case of a peripheral ameloblastoma arising in the buccal mucosa of which histological feature was confused with basal cell carcinoma, and review literatures concerning the histogenesis of the peripheral ameloblastoma and the differentiation from basal cell carcinoma.       CASE REPORT A 46-year-old Japanese man was referred tothe Otolaryngology Clinic at our hospital for the evaluation of a raised, tender, friable mass on the right buccal mucosa. The lesion had been present for a few months, and except for the tenderness it was asymptomatic. The clinical diagnosis was basal cell carcinoma. After surgical excision, the microscopic examination revealed that the lesion was mainly composed of a superficial proliferation of epithelial islands arising from overlying surface epithelium (Fig. 1), and individual islands were sometimes attached to the basilar layer of the overlying epithelium (Fig. 2). The outer layers of the islands consisted of palisaded columnar cells with their nuclei polarized away from the basement membrane. In the central area of the lesion, there was a stellate reticulum arrangement with occasional acanthomatous areas. Based on these histological findings, a diagnosis of basal cell carcinoma with ameloblastomatousfeatures, was made.  Seven years after the initial treatment, a tumor occurred at the right buccal mucosa near the maxilla. The second surgical excision was performad, and the lesion was diagnosed as basal cell adenoma (Fig. 3) by another pa-thologist.  Six years after the second operation, a third lesion was noted at the same location as the previous second lesion. The third surgical excision of the tumor was done. A diagnosis of peripheral ameloblastoma, follicular type, was made (Fig. 4).  These tumors were immunohistochemically examined in paraffin-embedded tissues by the ABC methods previously described (6). Lectins such as Con A, UEA-I, WGA, PNA, and SBA (EY Lab. INC) and antibody for keratin (DAKO) were used. Immunohistochemical results are shown in Table 1. The presence of LectinFig. 1. Islands and nest of tumor epithelium lying       below the surface epithelium (Hematoxylin       and Eosin stain x 100).Fig. 3. Lesion diagnosed as basal cell adenoma:       Similarity to the ameloblastoma (Hematoxy        lin and Eosin stain X30).Fig. 2. Island of ameloblastomatous tissue in       continuity with the surface mucosa      (Hematoxylin and Eosin stain X300).Fig. 4. Peripheral ameloblastoma, follicular type.       The epithelium is arranged in discrete islets       (Hematoxylin and Eosin stain X30).Fig. 5. Immunohistochemical staining for Con A       binding. Inner cells of the lesion are more      positive than outer layer (ABC Method x      300).binding and keratin was slightly more remark-able in the inner layers than in the outer layers of the lesion (Fig. 5).         DISCUSSION  The peripheral ameloblastoma is the rare tumor which is usually found in the mandibular molar area (14) and in the maxillary gingiva (11). Only three cases of the peripheral amelobla-stoma arising from buccal mucosa have been reported (2, 10,13) (Table 1).  The histologic apperance of the peripheral ameloblastoma _is almost the same as that of the central ameloblastoma (12, 14). The basal cell adenoma may resemble the ameloblastoma (13). The histologic features of the second lesion of the present case were similar to that of peripheral ameloblastoma, follicular type. such as the third lesion. The first pathological diagnosis of the present case was reported as basal cell carcinoma with ameloblastomatous features. We reviewed the histology of the first tumor and we could diagnose it as peripheral ameloblastoma, basal cell type. Simpson re-ported (11) a case of basal cell carcinoma withameloblastomatous lesion as our case, describ-ing that the histologic appearance was not exclusive to ameloblastoma. Thus, the differ-entiation between the peripheral amelobla-stoma, especially acanthomatous or basal type, and the intraoral basal cell carcinoma is sometimes confused.  Greer and Hammond (5) believed that the peripheral ameloblastoma exhibits central polarization of the nuclei of the peripheral cells, while the true intraoral basal cell carcinoma shows a sharp demarcation' between the peripheral cells and the central reticular cells. On the other hand, Gardner (4) considered these two lesions to be indistinguishable. The ultra-structural findings of previously reported cases (5) are rather nonspecific. The immunohisto-chemical examination of this present case showed almost the same findings as those of the case that was reported by Yamamoto et al. (14). They stated that immunohistochemical study disclosed no significant differences between peripheral ameloblastoma and basal cell carcinoma. We suppose that most of the authors (4, 9, 11, 13) consider the peripheral ameloblastoma and the oral basal cell carcinoma as the same lesion.  Lucas indicated that the possible origin of the tumor was the oral mucosa or cell rests (8). In many cases including our case (Fig, 2), there is an epithelial continuity between the tumor cells and the overlying basal epithelial cells. Therefore, it is not surprising that peripheral ameloblastoma or intraoral basal cell carcinoma arise from the basal cell layer of the oral mucosa overlying the alveolar processes (3, 8, 13).  However, it is difficult to explain the origin of peripheral ameloblastoma arising in the buccal mucosa on the basis of dental lamina rest proliferation, because of the rare occurrence of dental lamina rest in such a location. Although the possibility of salivary gland (rests            Table 1. Lectin binding and keratin in peripheral ameloblastoma              Con A UEA-I WGA PNA SBA Keratin Outer layer - ± - - - + Inner layer + ± ± ± ± ±           Table 2. Cases of peripheral ameloblastoma of the buccal mucosa Reference Age, sex, Location Continuity with Recurrence                      race basal layer     2 63 yr, male, Left Unstated -                 white    6 68 yr, male, Right + -                 Oriental    13 52 yr, female, Right + -               East Indian Present 46 yr, male, Right + +   case Japanese (7 yrs later)of Serres) origin or remnants of the vestibular lamina cannot be ruled out (4, 7), Woo et al. (13) consider that its origin would most probably be pluripotant cells in the overlying basal layer. Besides, they refer to the origin of the both lesions in the oral cavity : it is either from the pluripotent cells as above described or from native or ectopic epithelial rests. If this is the case, it is easy to explain the phenomenon of our case that peripheral ameloblastomas was observed in the same location after the complete local excision of basal cell carcinoma. That is to say, peripheral ameloblastoma and basal cell carcinoma of the oral cavity would be identical in origin, and the pluripotent cells could differentiate into peripheral ameloblastoma or basal cell carcinoma. Controversial matter about these lesions seem to be of semantics, since the same lesion may be observed from different aspects. We propose that pathological diagno-ses should be periphral ameloblastoma when more than half area of the lesion include follicular or plexiform pattern which resembles the enamel organ of the developing tooth germ.  Most authors have reported that peripheral ameloblastomas possess innocuous nature, and that conservative surgery is recommended. Nevertheless, Woo et al stated (13) that recur-rences were observed in all cases that were treated by simple local excision of the lesion. The tumors repeatedly occurred in the same lesion of the present case in spite of twice local excision. Whether recurrences of the tumor frequently occur or not, patients should be kept under periodic observation.         REFERENCES 1) Bernier., J. L.: The management of oral disease.   ST Louis, CV Mosby Co, 1955, p. 689. 2) Braunstein, E.: Case report of an extraosseous    adamantinoblastomma. Oral Surg Oral Med Oral   Pathol 2 : 726-728, 1949. 3) Ficarra, G. and Hansen, L. S.: Peripheral    ameloblastoma : A case report. J Cranio-Max-Fac    Surg 15:110-112, 1987. 4) Gardner, D.: Peripheral ameloblastoma, Cancer   35:1625-1633, 1977. 5) Greer, R. O. and Hammond, S. W.: Extraosseous    ameloblastoma : Light microscopic and ultra-   structural observarions. J Oral Surg 36: 553-556,   1978. 6) Hsu, S-H., Raine, L., and Fanger, H.: Use of    avidin-biotin-peroxidase complex (ABC)    inmmunoperoxidase techniques : A comparison   between ABC and unlabeled antibody (PAP)    procedures. J Histochem Cytochem 29:577-580   (1981). 7) Klina:, K. L. and McManis, J. C.: Soft tissue    ameloblastoma. Oral Surg Oral Med Oral Pathol   28:226-272, 1969. 8) Lucas, R. B.: Pathology of tumours of the oral    tissues. 4th Ed., Churchill Livingstone, London :   pp36, 1984. 9) Peter, R. A., Gingrass, R. P., Reyer, C. N. and    Hintz, C. S.: Basal cell carcinoma of the oral    cavity : report of case. J Oral Surg 30: 63-66, 1972. 10) Shafer, W. G., Hine, M. K. and Levy, B. M.: A    textbook of oral pathology, ed. 4, Philadelphia,    1983, W. B. Saunders Co., pp. 276-285. 11) Simpson, H. E.: Basal cell carcinoma and    peripheral ameloblastoma. Oral Surg Oral Med    Oral Pathol 38: 233-240, 1974. 12) Shiba, R., Sakoda, S. and Yamada N.: Peripheral    ameloblastoma. J Oral Maxillofac Surg 41 :460-  463, 1983. 13) Woo, S. B. Smith-williams, J. E., Sciubba, J. J.,    and Lipper, S.: Peripheral ameloblastoma of the    buccal mucosa : Case report and review of the   English literature. Oral Surg Oral Med Oral   Pathol 63: 78-84, 1987.14) Yamamoto, T., Ueta, E., Yoneda, K. and Osaki,    T.: Peripheral ameloblastoma : Case report with    immunohistochemical investigation. J Oral   Maxillofac Surg 48:197-200, 1990.

PERIPHERAL AMELOBLASTOMA OF THE BUCCAL MUCOSA : WITH A REVIEW OF THE LITERATURE

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PERIPHERAL AMELOBLASTOMA OF THE BUCCAL MUCOSA : WITH A REVIEW OF THE LITERATURE

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