J Oral Maxillofac 49:97&974.
Surg
1991
Peripheral Ameloblastoma: A Clinical and Histologic SAMIR
K. EL-MOFTY,
DMD,
Study of I I Cases
PHD,* NICHOLAS
0. GERARD,
DMD,t
SAM E. FARISH, DMD,$ AND BRAD RODU, DDS§ Peripheral ameloblastoma (PA) is a rare odontogenic tumor. Previously, only 39 cases of PA had been reported in the English literature. In this article 11 additional cases of PA are presented. Concordance with previous cases was evident with regard to race, clinical appearance, and site of predilection. However, differences were observed with regard to age, sex distribution, and predominant histologic pattern. The average age in the current cases is younger, there is no male bias, and the most common histologic pattern is plexiform rather than follicular or acanthomatous. Recurrence following simple excision is rare, but has been reported. Longterm postoperative follow-up is recommended.
Peripheral ameloblastoma (PA), also known as extraosseous or soft tissue ameloblastoma, is a relatively uncommon odontogenic tumor that is histologically identical to the classic intraosseous ameloblastoma. Almost all previously reported cases of PA were published as single case reports. In a comprehensive review of the English language literature in 1987, Buchner and Sciubba’ reviewed 32 welldocumented cases, and since then three additional cases have been reported.2-4 In a study of 116 cases of ameloblastoma, Waldron and El-Mofty’ found that 5% were peripheral. In nearly all of the reported cases of PA, the tumor developed in the soft tissue overlying the alveolar bone. The occurrence of PA in other sites in the oral cavity has been reported in only four cases, three of which were on the buccal mucosa,6-8 and one of which was in the floor of the mouth.’ The term basal cell carcinoma
of the oral cavity has occasionally been used to describe PA. ‘.‘“-‘4 According to some authorities,15*‘6 this is a matter of semantics and the two lesions are the same. The purpose of this article is to review the clinical and histologic findings in 11 previously unpublished cases of PA and to compare our findings with those in the 39 published cases. Materials
Ten cases of PA were obtained from the tiles of Washington University School of Dental Medicine, which also contained cases from other oral pathology services received as part of an ongoing slide exchange-peer review program. Case number 11 was received from the St Louis VA Medical Center. In all cases received from other oral pathology services, there was complete concurrence with the diagnosis of the contributor.
* Professor of Oral Pathology, Department of Pathology, Washington University, School of Medicine, St Louis. t Resident in Oral and Maxillofacial Surgery, - . Vanderbilt University, Nashville, TN. $ Staff Oral and Maxillofacial Sureeon. Deoartment of Veterans Affairs Medical Center, St Louis. § Associate Professor, Oral Pathology, Department of Diagnostic Studies, University of Alabama School of Dentistry, Birmingham, AL. Address correspondence and reprint requests to Dr El-Mofty: Washington University School of Medicine, Division of Surgical Pathology, Oral Pathology Section, One Barnes Hospital Plaza, St Louis, MO 63110. I
0 1991 American geons
Association
and Methods
Results
.
of Oral and Maxillofacial
The demographic, clinical, and histologic findings in the I1 cases are summarized in Table 1. The age of the patients was known in 10 of the cases and ranged from 33 to 68 years; the average age was 47 years. Half of the cases occurred in the fourth decade, while the other half affected patients in their fifth decade and older. In the 10 cases where gender was known, the male to female ratio was 1: 1. Seven tumors (64%) occurred in the mandible, 4
Sur-
0278-2391/91/4909-0008$3.00/O
970
EL-MOFTY ET AL
Table 1.
971
Demographic Data and Diagnosis in 11 Cases of Peripheral Ameloblastoma
Case No.
Age (yr)
Sex
Race
I
33
F
NI
2 3%
Nl 50
NJ M
NI W
4
60
F
W
5 6
36 39
M M
W NI
7
39
F
8 9
34 60
10 11
Size
km)
Location L. mandible, lingual to no. I8 & no. 19 Maxillary tuberosity L. mandible lingual to no. 21 & no. 22 L. maxillary tuberosity
co.5
0.5 i I .o
W
Maxillary gingiva L. mandible lingual to no. 21 & no. 22 L. maxilla palatal to no. 12
F M
NI W
R. mandible between no. 29 & no. 30 L. mandible lingual to no. 21
NI I.0
50
F
W
Mandible retromolar area
NI
68
M
W
L. mandible retromolar area
0.5 0.4 NI
1.5
1.5
Histologic Type Follicular Plexiform Follicular with an acanthomatous component Plexiform with an acanthomatous component Plexiform Mixed plexiform and follicular with an acanthomatous component Mixed plexiform and follicular with an acanthomatous component Plexiform Plexiform dominant with a follicular and acanthomatous components Plexiform dominant with a follicular component Basal cell pattern
Abbreviation: NI, not indicated. * Recurred after excision.
on the lingual gingiva of the premolar area, 1 on the lingual gingiva of the molar area, and 2 in the retromolar area. Four tumors (36%) occurred in the soft tissues of the maxilla, 2 in the gingiva and 2 in the tuberosity. The majority of the lesions were clinically described as either papillary or nodular. The color in most cases resembled that of normal mucosa. Two cases were, however, described as red. The size of the lesions ranged from 0.4 to 1.5 cm in diameter,
FIGURE 1. Photomicrograph of lesion in case 5 showing typical plexiform pattern. The ameloblastic cells proliferate from the surface squamous epithelium (upper left corner) (hematoxylin-eosin stain, original magnification x 140).
with a mean size of 0.9 cm. Radiographic evidence of superficial bone resorption was noted in case number 11. At surgery this was shown to be pressure resorption (cupping or saucerization) as opposed to neoplastic invasion of bone. The overall histologic features in the 11 cases were similar to those of the classical central ameloblastoma described in detail in other reports.“-‘” Four cases were classified as plexiform (Fig 1) and 2 were follicular (Fig 2). Four other cases showed a
972
PERIPHERAL
AMELOBLASTOMA
FIGURE 2. Photomicrograph of lesion in case 3 showing follicular pattern of ameloblastoma. The stellatereticulum component shows areas of squamous metaplasia. The tumor cells are continuous with the surface epithelium (upper right comer) (hematoxylin-eosin stain, original magnification X 140).
mixture of plexiform and follicular patterns. In 2 of these, the plexiform pattern was dominant. Acanthomatous changes, as demonstrated by squamous metaplasia, were seen in 5 of the 11 cases (Fig 2). One case, number 11, was classified as a basal cell variant (Fig 3). Tumor cells were continuous with the surface epithelium in 9 cases (82%) (Figs 1 and 2) while in only 2 cases (18%) were we unable to detect such continuity.
Discussion The occurrence of PA in a significantly older age group than the classical intraosseous ameloblastoma is well documented,‘~‘8-20 with patient’s ages ranging from 23 to 92 years. The mean age in the 32 cases of PA reviewed by Buchner and Sciubba’ was 52 years. The average age of patients with the intraosseous ameloblastoma is calculated to be 39
FIGURE 3. Photomicrograph of case 11 showing basal cell pattern. Sheets of densely packed basal cells replace the stellate-reticulum component which is typically seen in the classical follicular or plexiform patterns (hematoxyiineosin stain, original magnification X 3001.
EL-MOFTY ET AL
years.‘O The average age of incidence in the present 1I cases was 47 years, or more than 8 years older than in the case of the intraosseous ameloblastoma.” It is of interest that the age in the current group was slightly lower than in previously reported cases of PA and half of them occurred in the fourth decade. The gender distribution in the present cases was also at slight variance from previously reported cases. The male to female ratio in this study was I : 1 as compared to 1.9: 1 in the previous reports.‘-4 The current 11 cases show no gender bias, a finding shared with reported cases of intraosseous ameloblastoma.” All of the 7 patients where race was indicated (Table I) were white. This predilection has also been previously shown.’ Two thirds of the previously reported caseslm4 of PA and two thirds of the present ones occurred in the mandibular mucosa, predominantly the lingual gingiva of the premolar area. The second most common mandibular site was the molar-retromolar area. One third of the current and previously reported cases’-4 affected the soft tissues of the maxillary gingiva. particularly the tuberosity area. The intraosseous ameloblastoma also shows a marked predilection for the mandible (81%) according to Small and Waldron.‘” Bone involvement in PA is rare. When it occurs, it is in the form of superficial erosion rather than neoplastic invasion. The effect on the underlying bone has been described as cupping or saucerization, but it has been reported in only two previous cases’ and one of the current ones. Several histologic patterns of ameloblastoma are commonly described and include the follicular, plexiform, acanthomatous, granular cell, and basal cell patterns. ” In the present study, the plexiform pattern was the most prevalent. It was evident in 8 of the 11 cases (73%). In 4 of these, the plexiform pattern was mixed with the follicular component and it dominated in 2 of these 4 cases. This finding contrasts with observations on intraosseous ameloblastoma in which the follicular pattern is the most common. I9 The follicular pattern was also reported by Waldron and El-Mofty’ to be the most common histologic pattern seen in PA. This discrepancy might be due to limited numbers of cases studied. In this study acanthomatous changes were a common finding and were observed in 5 of the 11 cases. In none of these cases were these changes dominant enough to warrant a separate classification of acanthomatous ameloblastoma. This is in contrast with the findings in the study of 32 cases of PA by Buchner and Sciubba’ in which the most common pattern was acanthomatous. Only 1 of the present 11 cases
973
was of the basal cell type. Interestingly, a recently reported case of PA had a clear cell component.4 This feature has not been previously described in PA. So far the granular cell pattern has not been reported in PA. In 70% of previously reported cases of PA, direct continuity of the tumor with surface epithelium was noted.lB4 In the 11 cases reported here, 9 (82%) showed such continuity (Figs 1 and 2). Thus, in the majority of PA, a connection between the tumor and surface epithelium can be established. Two histogenetic origins for the PA have been proposed. Tumors that show complete separation from overlying surface epithelium probably arise from odontogenic epithelial remnants.” Tumors showing direct extension from the surface epithelium may arise from the basal cell layer of the overlying epithelium,” although a collision phenomenon cannot be entirely ruled out. Gardner15 and Waldron16 believe that the peripheral ameloblastoma and gingival basal cell carcinoma are probably one and the same. While no electronmicroscopic differences between the cells of ameloblastoma and basal cell carcinoma can be found, Greer and Hammond believe that the tumors can be distinguished by the reversed polarization of the nuclei of the palisaded peripheral columnar cells and the sharp demarcation between these cells and the central reticular cells in PA.‘3 Histochemical findings based on features revealed from a single case were not helpful in determining the histogenesis of PA.’ The accepted surgical treatment of the peripheral ameloblastoma involves excision of the lesion down to periosteum and including a small amount of normal tissue, generally without the removal of teeth.14 In 19% of cases reviewed by Buchner and Sciubba, recurrence was noted at times ranging from 2 months to 7 years.’ One of our cases also recurred after excision. These findings support the recommended long-term follow-up. Acknowledgment We thank the pathologists from University of Alabama and Temple University for their permission to use their cases from the slide exchange program in this study.
References 1. Buchner A, Sciubba JJ: Peripheral epithelial odontogenic tumors: A review. Oral Surg 63:688, 1987 2. Clark DB, Priddy RW. Seth VK: Peripheral ameloblastoma: Report of case. Can Dent Assoc J 54:35. 1988 3. Yamamoto T, Ueta E, Yoneda K. et al: Peripheral ameloblastoma: Case report with immunohistochemical investigation. J Oral Maxillofac Surg 48:197, 1990
DISCUSSION
974
4. Ng KH, Siar CH: Peripheral ameloblastoma with clear cell differentiation. Oral Surg 70:210, 1990 5. Waldron CA, El-Mofty SK: A histopathologic study of 116 ameloblastomas with special reference to the desmoplastic variant. Oral Surg 63:441, 1987 6. Woo S. Smith-Williams JE. Sciubba JJ. et al: Peripheral amelbblastoma of the buccal mucosa: Case report and review of the English literature. Oral Surg 63:78, 1987 7. Braunstein E: Case report of an extraosseous adamantinoblastoma. Oral Surg 2:726, 1949 8. Klinar KL, McManis JC: Soft-tissue ameloblastoma: Report of a case. Oral Surg 28:266, 1969 9. Ramnarayan K, Nayak RG, Kavalam AG: Peripheral ameloblastoma. Int J Oral Surg 14:300. 1985 10. Lawson BF, Griffen JW, Waldron CA: Basal cell carcinoma of the gingiva. Oral Surg 24:648, 1967 11. Williamson JJ, Cohney BC, Henderson BM: Basal cell carcinoma of the mandibular gingiva. Arch Dermatol 95:76. 1967 12. Liroff KP, Zeff S: Basal cell carcinoma of the palatal mucosa. J Oral Surg 30:730, 1972 13. Peters RA, Gingrass RP, Reyes CN, et al: Basal cell carcinoma of the oral cavity: Report of case. J Oral Surg 30:63, 1972 14. Samit AM: Intraoral basal cell carcinoma. J Surg Oncol 10:27, 1978
J Oral Maxillofac 49:974-975.
15. Gardner DG: Peripheral ameloblastoma: A study of 21 cases, including 5 reported as basal cell carcinoma of the gingiva. Cancer 39:1625, 1977 16. Waldron CA: Comment on Peters RA, Gingrass RP, Reyes CN, Hintz CS: Basal cell carcinoma of the oral cavity: Report of case. J Oral Surg 30:66, 1972 17. Pindborg JJ, Kramer IRH, Torloni H: Histological typing of odontogenic tumors, jaw cysts, and allied lesions. International Histological Classification of Tumors no. 5. Geneva, World Health Organization, 1971 18. Shafer WG, Hine MK, Levy BM: A textbook of oral Pathology (ed 4). Philadelphia, PA, Saunders, 1983 19. Regezi JA, Sciubba JJ: Oral pathology: Clinical-pathologic correlations. Philadelphia, PA, Saunders, 1989 20. Small IA, Waldron CA: Ameloblastoma of the jaws. Oral Surg 8:281, 1955 21. Stanley HR Jr, Krogh HW: Peripheral ameloblastoma: Report of a case. Oral Surg 12:760, 1959 22. Aisenberg MS: Histopathology of ameloblastoma. Oral Surg 6:1111, 1953 23. Greer RO Jr, Hammond WS: Extraosseous ameloblastoma: Light and ultrastructural observations. J Oral Surg 36:553, 1978 24. Gardner DG: A pathologist’s approach to the treatment of ameloblastoma. J Oral Maxillofac Surg 42: 161, 1984
Surg
1991
Discussion Peripheral Ameloblastoma: A Clinical and Histologic Study of 11 Cases James
J. Sciubba,
Long Island Jewish
DMD, PhD
Medical
Center,
New Hyde Park, NY
Drs El-Mofty, Gerard, Farish, and Rodu have made a significant contribution to the literature on peripheral ameloblastoma and peripheral odontogenic tumors in general. The material was well presented and is in agreement with the current body of information on the subject. Their experience in general parallels both the demographics as well as clinical presentation and histology of this important entity. What is often lacking, as in the case of this article, however, is information about the clinical perspective and presentation. In our experience, a wide range of clinical impressions is often evident when reviewing clinical data prior to microscopic examination of these lesions. While such peripheral odontogenic neoplasms, typified by the ameloblastoma, are benign and generally slow growing, clinicians will often state that pyogenie granuloma, peripheral giant cell granuloma, or other benign soft tissue tumors are their first clinical or diagnostic choice. Emphasis should be directed toward lesions arising on the attached gingiva, which could possibly be representative of a benign odontogenic neoplasm. When such benign neoplasms are traumatized, a
clinical diagnosis will often include pyogenic granuloma as well. In nearly all peripheral ameloblastomas there is a distinctive difference in behavior and biologic potential when compared to the intraosseous or central counterpart, regardless of the histologic subtype. A biologic explanation for this difference remains elusive, yet nonetheless appears to be consistent. The issue of histogenesis of the peripheral ameloblastoma is a somewhat controversial one, with most authorities favoring origin by direct extension from the overlying surface epithelium. The resemblance to certain forms of cutaneous neoplasms, namely the basal cell carcinoma, must be considered. The similarity of the intraoral lesion to the adamantinoid trichoblastoma is likewise worthy of mention, although there are sufficient histologic differences between the latter entity and peripheral ameloblastoma. These include the absence of any form of follicular differentiation within the ameloblastoma, no evidence of stromal features within the ameloblastoma resembling the perifollicular sheath, and an absence of clefts within the stroma of the peripheral ameloblastoma. The similarity, however, between the peripheral ameloblastoma and the basal cell carcinoma at a histologic level relates to the connection with the surface epithelium, an absence of mitotic figures, few or no signs of specific differentiation, a predominance of the epithelial over the stromal component, and both sheeting as well as cribriform patterns of cells. It seems safe to say, therefore, that while some structural similarities exist between the peripheral ameio-
Surg
1991
Peripheral Ameloblastoma: A Clinical and Histologic SAMIR
K. EL-MOFTY,
DMD,
Study of I I Cases
PHD,* NICHOLAS
0. GERARD,
DMD,t
SAM E. FARISH, DMD,$ AND BRAD RODU, DDS§ Peripheral ameloblastoma (PA) is a rare odontogenic tumor. Previously, only 39 cases of PA had been reported in the English literature. In this article 11 additional cases of PA are presented. Concordance with previous cases was evident with regard to race, clinical appearance, and site of predilection. However, differences were observed with regard to age, sex distribution, and predominant histologic pattern. The average age in the current cases is younger, there is no male bias, and the most common histologic pattern is plexiform rather than follicular or acanthomatous. Recurrence following simple excision is rare, but has been reported. Longterm postoperative follow-up is recommended.
Peripheral ameloblastoma (PA), also known as extraosseous or soft tissue ameloblastoma, is a relatively uncommon odontogenic tumor that is histologically identical to the classic intraosseous ameloblastoma. Almost all previously reported cases of PA were published as single case reports. In a comprehensive review of the English language literature in 1987, Buchner and Sciubba’ reviewed 32 welldocumented cases, and since then three additional cases have been reported.2-4 In a study of 116 cases of ameloblastoma, Waldron and El-Mofty’ found that 5% were peripheral. In nearly all of the reported cases of PA, the tumor developed in the soft tissue overlying the alveolar bone. The occurrence of PA in other sites in the oral cavity has been reported in only four cases, three of which were on the buccal mucosa,6-8 and one of which was in the floor of the mouth.’ The term basal cell carcinoma
of the oral cavity has occasionally been used to describe PA. ‘.‘“-‘4 According to some authorities,15*‘6 this is a matter of semantics and the two lesions are the same. The purpose of this article is to review the clinical and histologic findings in 11 previously unpublished cases of PA and to compare our findings with those in the 39 published cases. Materials
Ten cases of PA were obtained from the tiles of Washington University School of Dental Medicine, which also contained cases from other oral pathology services received as part of an ongoing slide exchange-peer review program. Case number 11 was received from the St Louis VA Medical Center. In all cases received from other oral pathology services, there was complete concurrence with the diagnosis of the contributor.
* Professor of Oral Pathology, Department of Pathology, Washington University, School of Medicine, St Louis. t Resident in Oral and Maxillofacial Surgery, - . Vanderbilt University, Nashville, TN. $ Staff Oral and Maxillofacial Sureeon. Deoartment of Veterans Affairs Medical Center, St Louis. § Associate Professor, Oral Pathology, Department of Diagnostic Studies, University of Alabama School of Dentistry, Birmingham, AL. Address correspondence and reprint requests to Dr El-Mofty: Washington University School of Medicine, Division of Surgical Pathology, Oral Pathology Section, One Barnes Hospital Plaza, St Louis, MO 63110. I
0 1991 American geons
Association
and Methods
Results
.
of Oral and Maxillofacial
The demographic, clinical, and histologic findings in the I1 cases are summarized in Table 1. The age of the patients was known in 10 of the cases and ranged from 33 to 68 years; the average age was 47 years. Half of the cases occurred in the fourth decade, while the other half affected patients in their fifth decade and older. In the 10 cases where gender was known, the male to female ratio was 1: 1. Seven tumors (64%) occurred in the mandible, 4
Sur-
0278-2391/91/4909-0008$3.00/O
970
EL-MOFTY ET AL
Table 1.
971
Demographic Data and Diagnosis in 11 Cases of Peripheral Ameloblastoma
Case No.
Age (yr)
Sex
Race
I
33
F
NI
2 3%
Nl 50
NJ M
NI W
4
60
F
W
5 6
36 39
M M
W NI
7
39
F
8 9
34 60
10 11
Size
km)
Location L. mandible, lingual to no. I8 & no. 19 Maxillary tuberosity L. mandible lingual to no. 21 & no. 22 L. maxillary tuberosity
co.5
0.5 i I .o
W
Maxillary gingiva L. mandible lingual to no. 21 & no. 22 L. maxilla palatal to no. 12
F M
NI W
R. mandible between no. 29 & no. 30 L. mandible lingual to no. 21
NI I.0
50
F
W
Mandible retromolar area
NI
68
M
W
L. mandible retromolar area
0.5 0.4 NI
1.5
1.5
Histologic Type Follicular Plexiform Follicular with an acanthomatous component Plexiform with an acanthomatous component Plexiform Mixed plexiform and follicular with an acanthomatous component Mixed plexiform and follicular with an acanthomatous component Plexiform Plexiform dominant with a follicular and acanthomatous components Plexiform dominant with a follicular component Basal cell pattern
Abbreviation: NI, not indicated. * Recurred after excision.
on the lingual gingiva of the premolar area, 1 on the lingual gingiva of the molar area, and 2 in the retromolar area. Four tumors (36%) occurred in the soft tissues of the maxilla, 2 in the gingiva and 2 in the tuberosity. The majority of the lesions were clinically described as either papillary or nodular. The color in most cases resembled that of normal mucosa. Two cases were, however, described as red. The size of the lesions ranged from 0.4 to 1.5 cm in diameter,
FIGURE 1. Photomicrograph of lesion in case 5 showing typical plexiform pattern. The ameloblastic cells proliferate from the surface squamous epithelium (upper left corner) (hematoxylin-eosin stain, original magnification x 140).
with a mean size of 0.9 cm. Radiographic evidence of superficial bone resorption was noted in case number 11. At surgery this was shown to be pressure resorption (cupping or saucerization) as opposed to neoplastic invasion of bone. The overall histologic features in the 11 cases were similar to those of the classical central ameloblastoma described in detail in other reports.“-‘” Four cases were classified as plexiform (Fig 1) and 2 were follicular (Fig 2). Four other cases showed a
972
PERIPHERAL
AMELOBLASTOMA
FIGURE 2. Photomicrograph of lesion in case 3 showing follicular pattern of ameloblastoma. The stellatereticulum component shows areas of squamous metaplasia. The tumor cells are continuous with the surface epithelium (upper right comer) (hematoxylin-eosin stain, original magnification X 140).
mixture of plexiform and follicular patterns. In 2 of these, the plexiform pattern was dominant. Acanthomatous changes, as demonstrated by squamous metaplasia, were seen in 5 of the 11 cases (Fig 2). One case, number 11, was classified as a basal cell variant (Fig 3). Tumor cells were continuous with the surface epithelium in 9 cases (82%) (Figs 1 and 2) while in only 2 cases (18%) were we unable to detect such continuity.
Discussion The occurrence of PA in a significantly older age group than the classical intraosseous ameloblastoma is well documented,‘~‘8-20 with patient’s ages ranging from 23 to 92 years. The mean age in the 32 cases of PA reviewed by Buchner and Sciubba’ was 52 years. The average age of patients with the intraosseous ameloblastoma is calculated to be 39
FIGURE 3. Photomicrograph of case 11 showing basal cell pattern. Sheets of densely packed basal cells replace the stellate-reticulum component which is typically seen in the classical follicular or plexiform patterns (hematoxyiineosin stain, original magnification X 3001.
EL-MOFTY ET AL
years.‘O The average age of incidence in the present 1I cases was 47 years, or more than 8 years older than in the case of the intraosseous ameloblastoma.” It is of interest that the age in the current group was slightly lower than in previously reported cases of PA and half of them occurred in the fourth decade. The gender distribution in the present cases was also at slight variance from previously reported cases. The male to female ratio in this study was I : 1 as compared to 1.9: 1 in the previous reports.‘-4 The current 11 cases show no gender bias, a finding shared with reported cases of intraosseous ameloblastoma.” All of the 7 patients where race was indicated (Table I) were white. This predilection has also been previously shown.’ Two thirds of the previously reported caseslm4 of PA and two thirds of the present ones occurred in the mandibular mucosa, predominantly the lingual gingiva of the premolar area. The second most common mandibular site was the molar-retromolar area. One third of the current and previously reported cases’-4 affected the soft tissues of the maxillary gingiva. particularly the tuberosity area. The intraosseous ameloblastoma also shows a marked predilection for the mandible (81%) according to Small and Waldron.‘” Bone involvement in PA is rare. When it occurs, it is in the form of superficial erosion rather than neoplastic invasion. The effect on the underlying bone has been described as cupping or saucerization, but it has been reported in only two previous cases’ and one of the current ones. Several histologic patterns of ameloblastoma are commonly described and include the follicular, plexiform, acanthomatous, granular cell, and basal cell patterns. ” In the present study, the plexiform pattern was the most prevalent. It was evident in 8 of the 11 cases (73%). In 4 of these, the plexiform pattern was mixed with the follicular component and it dominated in 2 of these 4 cases. This finding contrasts with observations on intraosseous ameloblastoma in which the follicular pattern is the most common. I9 The follicular pattern was also reported by Waldron and El-Mofty’ to be the most common histologic pattern seen in PA. This discrepancy might be due to limited numbers of cases studied. In this study acanthomatous changes were a common finding and were observed in 5 of the 11 cases. In none of these cases were these changes dominant enough to warrant a separate classification of acanthomatous ameloblastoma. This is in contrast with the findings in the study of 32 cases of PA by Buchner and Sciubba’ in which the most common pattern was acanthomatous. Only 1 of the present 11 cases
973
was of the basal cell type. Interestingly, a recently reported case of PA had a clear cell component.4 This feature has not been previously described in PA. So far the granular cell pattern has not been reported in PA. In 70% of previously reported cases of PA, direct continuity of the tumor with surface epithelium was noted.lB4 In the 11 cases reported here, 9 (82%) showed such continuity (Figs 1 and 2). Thus, in the majority of PA, a connection between the tumor and surface epithelium can be established. Two histogenetic origins for the PA have been proposed. Tumors that show complete separation from overlying surface epithelium probably arise from odontogenic epithelial remnants.” Tumors showing direct extension from the surface epithelium may arise from the basal cell layer of the overlying epithelium,” although a collision phenomenon cannot be entirely ruled out. Gardner15 and Waldron16 believe that the peripheral ameloblastoma and gingival basal cell carcinoma are probably one and the same. While no electronmicroscopic differences between the cells of ameloblastoma and basal cell carcinoma can be found, Greer and Hammond believe that the tumors can be distinguished by the reversed polarization of the nuclei of the palisaded peripheral columnar cells and the sharp demarcation between these cells and the central reticular cells in PA.‘3 Histochemical findings based on features revealed from a single case were not helpful in determining the histogenesis of PA.’ The accepted surgical treatment of the peripheral ameloblastoma involves excision of the lesion down to periosteum and including a small amount of normal tissue, generally without the removal of teeth.14 In 19% of cases reviewed by Buchner and Sciubba, recurrence was noted at times ranging from 2 months to 7 years.’ One of our cases also recurred after excision. These findings support the recommended long-term follow-up. Acknowledgment We thank the pathologists from University of Alabama and Temple University for their permission to use their cases from the slide exchange program in this study.
References 1. Buchner A, Sciubba JJ: Peripheral epithelial odontogenic tumors: A review. Oral Surg 63:688, 1987 2. Clark DB, Priddy RW. Seth VK: Peripheral ameloblastoma: Report of case. Can Dent Assoc J 54:35. 1988 3. Yamamoto T, Ueta E, Yoneda K. et al: Peripheral ameloblastoma: Case report with immunohistochemical investigation. J Oral Maxillofac Surg 48:197, 1990
DISCUSSION
974
4. Ng KH, Siar CH: Peripheral ameloblastoma with clear cell differentiation. Oral Surg 70:210, 1990 5. Waldron CA, El-Mofty SK: A histopathologic study of 116 ameloblastomas with special reference to the desmoplastic variant. Oral Surg 63:441, 1987 6. Woo S. Smith-Williams JE. Sciubba JJ. et al: Peripheral amelbblastoma of the buccal mucosa: Case report and review of the English literature. Oral Surg 63:78, 1987 7. Braunstein E: Case report of an extraosseous adamantinoblastoma. Oral Surg 2:726, 1949 8. Klinar KL, McManis JC: Soft-tissue ameloblastoma: Report of a case. Oral Surg 28:266, 1969 9. Ramnarayan K, Nayak RG, Kavalam AG: Peripheral ameloblastoma. Int J Oral Surg 14:300. 1985 10. Lawson BF, Griffen JW, Waldron CA: Basal cell carcinoma of the gingiva. Oral Surg 24:648, 1967 11. Williamson JJ, Cohney BC, Henderson BM: Basal cell carcinoma of the mandibular gingiva. Arch Dermatol 95:76. 1967 12. Liroff KP, Zeff S: Basal cell carcinoma of the palatal mucosa. J Oral Surg 30:730, 1972 13. Peters RA, Gingrass RP, Reyes CN, et al: Basal cell carcinoma of the oral cavity: Report of case. J Oral Surg 30:63, 1972 14. Samit AM: Intraoral basal cell carcinoma. J Surg Oncol 10:27, 1978
J Oral Maxillofac 49:974-975.
15. Gardner DG: Peripheral ameloblastoma: A study of 21 cases, including 5 reported as basal cell carcinoma of the gingiva. Cancer 39:1625, 1977 16. Waldron CA: Comment on Peters RA, Gingrass RP, Reyes CN, Hintz CS: Basal cell carcinoma of the oral cavity: Report of case. J Oral Surg 30:66, 1972 17. Pindborg JJ, Kramer IRH, Torloni H: Histological typing of odontogenic tumors, jaw cysts, and allied lesions. International Histological Classification of Tumors no. 5. Geneva, World Health Organization, 1971 18. Shafer WG, Hine MK, Levy BM: A textbook of oral Pathology (ed 4). Philadelphia, PA, Saunders, 1983 19. Regezi JA, Sciubba JJ: Oral pathology: Clinical-pathologic correlations. Philadelphia, PA, Saunders, 1989 20. Small IA, Waldron CA: Ameloblastoma of the jaws. Oral Surg 8:281, 1955 21. Stanley HR Jr, Krogh HW: Peripheral ameloblastoma: Report of a case. Oral Surg 12:760, 1959 22. Aisenberg MS: Histopathology of ameloblastoma. Oral Surg 6:1111, 1953 23. Greer RO Jr, Hammond WS: Extraosseous ameloblastoma: Light and ultrastructural observations. J Oral Surg 36:553, 1978 24. Gardner DG: A pathologist’s approach to the treatment of ameloblastoma. J Oral Maxillofac Surg 42: 161, 1984
Surg
1991
Discussion Peripheral Ameloblastoma: A Clinical and Histologic Study of 11 Cases James
J. Sciubba,
Long Island Jewish
DMD, PhD
Medical
Center,
New Hyde Park, NY
Drs El-Mofty, Gerard, Farish, and Rodu have made a significant contribution to the literature on peripheral ameloblastoma and peripheral odontogenic tumors in general. The material was well presented and is in agreement with the current body of information on the subject. Their experience in general parallels both the demographics as well as clinical presentation and histology of this important entity. What is often lacking, as in the case of this article, however, is information about the clinical perspective and presentation. In our experience, a wide range of clinical impressions is often evident when reviewing clinical data prior to microscopic examination of these lesions. While such peripheral odontogenic neoplasms, typified by the ameloblastoma, are benign and generally slow growing, clinicians will often state that pyogenie granuloma, peripheral giant cell granuloma, or other benign soft tissue tumors are their first clinical or diagnostic choice. Emphasis should be directed toward lesions arising on the attached gingiva, which could possibly be representative of a benign odontogenic neoplasm. When such benign neoplasms are traumatized, a
clinical diagnosis will often include pyogenic granuloma as well. In nearly all peripheral ameloblastomas there is a distinctive difference in behavior and biologic potential when compared to the intraosseous or central counterpart, regardless of the histologic subtype. A biologic explanation for this difference remains elusive, yet nonetheless appears to be consistent. The issue of histogenesis of the peripheral ameloblastoma is a somewhat controversial one, with most authorities favoring origin by direct extension from the overlying surface epithelium. The resemblance to certain forms of cutaneous neoplasms, namely the basal cell carcinoma, must be considered. The similarity of the intraoral lesion to the adamantinoid trichoblastoma is likewise worthy of mention, although there are sufficient histologic differences between the latter entity and peripheral ameloblastoma. These include the absence of any form of follicular differentiation within the ameloblastoma, no evidence of stromal features within the ameloblastoma resembling the perifollicular sheath, and an absence of clefts within the stroma of the peripheral ameloblastoma. The similarity, however, between the peripheral ameloblastoma and the basal cell carcinoma at a histologic level relates to the connection with the surface epithelium, an absence of mitotic figures, few or no signs of specific differentiation, a predominance of the epithelial over the stromal component, and both sheeting as well as cribriform patterns of cells. It seems safe to say, therefore, that while some structural similarities exist between the peripheral ameio-
