Peripheral epithelial odontogenic tumors: A review

Peripheral epithelial odontogenic tumors: A . review Amos Buchner, D.M.D., M.S.D.,* and James J. Sciubba, D.M.D., Ph.D.,** Tel Aviv, Israel, and New Hyde Park, N.Y. SCHOOL OF DENTAL MEDICINE. LABORATORIES, LONG ISLAND

TEL AVIV UNIVERSITY, AND DEPARTMENTS JEWISH-HILLSIDE MEDICAL CENTER

OF DENTISTRY

AND

Peripheral (extraosseous or soft tissue) odontogenic tumors are rare lesions that occur in the soft tissue overlying the tooth-bearing areas of the mandible and the maxilla. A review of the English-language literature revealed only 48 well-documented cases of peripheral epithelial odontogenic tumors. Thirty-two were peripheral ameloblastomas; six were peripheral adenomatoid odontogenic tumors; nine were peripheral calcifying epithelial odontogenic tumors; and one was a peripheral squamous odontogenic tumor. An additional four cases were reported as peripheral ameloblastomas in extragingival locations, but their odontogenic origin is debatable. Although the peripheral ameloblastoma is histologically similar to its central counterpart, it differs in its clinical features and biologic behavior. It does not exhibit an aggressive, destructive behavior and does not invade the underlying bone. Conservative excision of the tumor with minimal but adequate margins is the treatment of choice and recurrences are uncommon. This benign biologic behavior appears to be true also for lesions diagnosed as peripheral calcifying epithelial odontogenic tumors and undoubtedly is true for the peripheral adenomatoid odontogenic tumors. (ORAL SURC. ORAL MED. ORAL PATHOL. 1987;63:688-97)

0

dontogenic tumors are uncommon lesions of the oral cavity. A study by Regezi and coworkers’ revealed that, as a group, odontogenic tumors represent only 1.3% of all the biopsy specimens (almost 5S,OOO)processedwithin their dental school biopsy service. Individually, odontomas accounted for more than two thirds of the group so that the appearance of the remainder of the tumors was a relatively rare occurrence-ameloblastoma accounting for 11% of the group, adenomatoid odontogenic tumor for 3%, and calcifying epithelial odontogenic tumor for less than 1%. Peripheral odontogenic tumors are defined as tumors that demonstrate the histologic characteristics of their intraosseous counterparts but occur solely in the soft tissue covering the tooth-bearing portion of the mandible and the maxilla. These lesions are also known as extraosseous odontogenic tumors or as soft tissue odontogenic tumors. They are exceedingly rare, and most of the reports in the literature have been single case reports. Odontogenic *Chairman, Section of Oral Pathology and Medicine. **Chairman, Department of Dentistry, and Attending Pathologist. Department of Laboratories.

666

Oral

tumors that have been described as originating in the gingiva include the ameloblastoma, the adenomatoid odontogenic tumor, the calcifying epithelial odontogenie tumor, the squamous odontogenic tumor, and the odontogenic fibroma (World Health Organization type), which according to the present concept includes cases published as gingival epithelial hamartoma (hamartoma of the dental lamina) and as ameloblastic fibrodentinoma.* Recently, a case of peripheral granular cell ameloblastic fibroma was reported.’ The calcifying odontogenic cyst is another lesion that can originate in the gingiva. However, the peripheral lesion is not as rare as the aforementioned odontogenic tumors. Gingival lesions have occurred in 21.5S4 and 29.%V of the cases reviewed in two comprehensive studies of calcifying odontogenic cysts. The purpose of the present article is to review the English-language literature and to analyze the clinical and histologic data of the rare epithelial peripheral odontogenic tumors-the peripheral ameloblastoma, the peripheral adenomatoid odontogenic tumor, the peripheral calcifying epithelial odontogenie tumor, and the peripheral squamous odontog-

Peripheral

Volume 63 Number 6

enic tumor. These, in turn, will be compared with their intraosseous counterparts. PERIPHERAL

AMELOBLASTOMA

The peripheral ameloblastoma (PA), also known as the extraosseousameloblastoma or as the ameloblastoma of soft tissues, is a tumor with the histologic characteristics of an intraosseous ameloblastoma but it occurs in the soft tissues overlying the toothbearing areas of the maxilla and the mandible. This definition excludes several questionable casesof PA reported elsewhere in the oral mucosa.6 Cases of basal cell carcinoma arising in the gingiva have also been reported. Currently, there is general agreement that the PA and the basal cell carcinoma of the gingiva are essentially one and the same lesion and, thus, should be regarded as a single entity.6-9 A search of the English-language literature disclosed 26 well-documented casesthat were reported as PA occurring in the gingiva and the alveolar mucosa8-32(Table I); 4 cases that were reported as PA in extragingival locations33-‘6(Table II); and 6 cases that were reported as basal cell carcinoma of the gingiva and the alveolar mucosa3’-“’ (Table III). There are other reports of PA that were not included in this study, either becausethe histopathology was not compatible with ameloblastoma or becausethe clinical data were insufficient. Thus, the case reported by Gullifer42 was excluded becausethe histopathologic description was not consistent with ameloblastoma, and the report by Zetz and coworkers43was excluded because of inadequate radiologic and histologic data with respect to the extraosseous nature of the lesion. Single cases4”j6were not included because of insufficient clinical data. For the purpose of analysis of the data, we have combined the 26 cases reported as PA of the toothbearing areas and the 6 casesreported as basal cell carcinoma of the gingiva. We have not included the 4 casesof extragingival PA. For the purpose of comparison between the PA and the intraosseous ameloblastoma, we have used the data from the comprehensive study of Small and Waldron,j’ which consisted of more than 1,000 casesof central ameloblastomas. Age, gender

distribution,

and race

The youngest patient was 23 years old and the oldest patient was 92 years old. The mean age at diagnosis was 52.3 years. The highest incidence was in the fifth and sixth decades, with 44% of the patients in these age groups.

epithelial

odontogenic tumors

689

The mean age at diagnosis for the intraosseous ameloblastoma was reported to be 38.9 years; nearly half of the tumors occurred in the third and fourth decades.Thus, PA occurs at a significantly older age than its central counterpart. Of the 32 peripheral lesions, 20 (62.5%) occurred in male patients and 12 (37.5%) occurred in female patients. The male-to-female ratio was 1.7:1. A slight male predominance has also been reported for the intraosseous ameloblastoma. The race of the patients was reported for 27 cases. Twenty patients were white, two were black, four were Asian, and one was Hispanic. The predominance in a specific race, however, is difficult to evaluate from a review of the English-language literature only. Location

The mandible is the more common site for PA, as shown by the occurrence of 19 (59%) of the lesions in the mandible and 13 (41%) of the lesions in the maxilla. In the mandible, 4 lesions occurred in the incisor region, 11 occurred in the canine-premolar area, and 4 occurred in the molar-retromolar region. It was of interest to note that 9 mandibular lesions were located in the lingual gingiva (1 in the incisor area and 8 in the canine-premolar area). In the maxilla, 1 lesion occurred in the incisor area, 2 occurred in the canine-premolar area (both of them in the palatal mucosa), and 10 occurred in the molar-retromolar area. Thus, the most common location in the maxilla was the soft tissue of the tuberosity area. The intraosseous ameloblastoma also shows a marked predilection for the mandible (81% of the cases). Seventy percent of these occur in the molarramus area, 20% occur in the premolar area, and 10% occur in the symphysis area. The less common lesions of the maxilla (19%) are found most frequently in the molar area. It is interesting to note that the most common location of the PA of the mandibular region was the canine-premolar area rather than the molar-ramus area of its intraosseous counterpart. Clinical

features

Most of the lesions occurred as growths that were painless, sessile, firm, and exophytic. The surface was usually relatively smooth but, in several cases,it was described as “granular” or “pebbly.” In two cases,the surface exhibited a “papillary” or “warty” appearance. The color of the lesion was usually described as “normal” or “pink” but, in some cases,

Buchner and Sciubba

690

Oral Surg. June, 1987

I. Published casesof peripheral ameloblastoma in tooth-bearing areas

Table

Case No.

Author

sex

Race*

Locationf R. mand. ling. between second premolar and first molar R. max. tuberosity area L. pal. between canine and first premolar R. mand. ling. premolars area L. mand. ling. incisors R. max. tuberosity area L. mand. ling. second premolar L. mand. eden. third molar area Man. ling. premolars

I

Stanley and Krogh ( 1959)‘O

34

F

W

2

Russell (1966)”

52

M

W

3

Lee et al. (1970)lz

35

M

A

4

Lee et al. (1970)”

47

M

A

5

23

F

W

6

Wertheimer and Stroud (1972)” Wallen (1972)”

82

M

W

7

Balfour et al. (1973)“

62

M

B

8

Simpson ( I974)*

28

M

W

9

47

F

W

45

F

W

II

Richardson and Greer (1974)‘b Pansino and Meara (1975)l’ Wesley et al. (1977)‘*

33

F

NI

12

Frankel et al. ( 1977)19

92

F

NI

13

Greer and Hammond (1978)‘” Birkholz et al. ( 1978)2’

43

F

W

58

M

NI

IO

14

NI--no *W-white; tR

Age

--right:

information. B-black: L-left:

A--Asian: mand.--mandible:

L. mand. canine and first premolar L. mand. edent. second molar area R. max. posterior eden. area L. max. tuberosity area R. mand. eden. incisors area

0.9

NI

0.5

NI

I .o

I mo.

1.5

8 mo.

NI

2 yr.

I .3

NI

0.4

NI

I.0

NI

1.3

NI

NI

NI

2.0

I yr.

2.0

3 mo.

0.8

NI

I .o

5 mo.

H-Hispanic. max.-maxilla;

ling.-lingual

gingiva:

it was “red” or “dark red.” In four cases,the lesion manifested itself as an ulceration. In four cases involving the maxillary tuberosity area, the clinician believed that the lesion was associated with an ill-fitting denture. A variety of preoperative diagnoses were made. The most common diagnosis was fibroma (fibrous hyperplasia), followed in decreasing order by pyogenie granuloma, peripheral giant cell granuloma, and papilloma. Squamous cell carcinoma was considered to be the sole preoperative diagnosis in two cases. Information with respect to the duration of the lesion was reported in 16 cases; it usually ranged from 1 month to 2 years. In one case, a 5-year duration was reported. The mean duration was 1 year. The size of the lesion was reported in 28 casesand

pal.--palatal

mucosa:

lab.-labial

mucosa:

eda--edentulour

usually ranged from 0.3 to 2.0 cm at the greatest diameter. In two cases,the lesions were 4 and 4.5 cm in diameter, respectively. The mean size of the lesions was 1.3 cm. In 29 cases, there was no radiologic evidence of bone involvement. In two cases,superficial erosion of the bone was seen, and in one case, no radiologic findings were mentioned. In five cases (15%), including the two casesin which the radiologic changes were exhibited, a superficial bony depression of the underlying bone-known as cupping or saucerization-was noted at surgery. This was alleged to be due to pressure resorption, in contrast to neoplastic invasion of bone. Histologic

features and histogenesis

The PA exhibits the same histomorphologic cell types and patterns as seenin the intraosseous amelo-

Peripheral

Volume 63 Number 6

epithelial

odontogenic tumors

691

I. Cont’d

Table

Case No.

Author

Age

Sex

Race*

Locationf L. mand. ling. between canine and first premolar R. mand. ling. first premolar L. max. eden. molar area R. mand. lab. between canine and first premolar L. max. second molar L. pal. second premolar R. max. tuberosity area L. mand. ling. between second premolar and first molar R. mand. lab. between central and lateral incisors L. mand. retromolar area R. mand. eden. premolar area R. mand. ling. between first and second premolars

I5

Gould et al. (1982)”

70

M

W

16

57

M

W

I7

Moskow and Baden ( I 982)9 Patrikiou et al. (1983)”

76

F

NI

I8

Shiba et al. (1983)”

28

M

A

I9

16

M

H

20

Urmacher and Pearlman (1983)” Guralnick et al. (1983)‘”

45

M

W

21

Schaberg et al. (1983)”

54

M

W

22

Ide et al. (1983)**

32

M

A

23

Connolly et al. ( 1984)19

55

F

B

24

Anneroth and Johansson (1985)‘O Ficarra and Hansen ( 1986)” Horowitz et al. ( 1987)j2

28

F

W

70

M

W

50

M

W

25 26

blastoma, namely, follicular, plexiform, basal cell, and acanthomatous. The most common pattern was the acanthomatous type, and most of the PAS were diagnosed microscopically as acanthomatous ameloblastomas. It is of interest to note that the granular cell pattern has not been described in the PA. Information with respect to the relationship of the tumor to the surface epithelium was available in 27 cases. In 19 cases (70%), there was a continuity between the tumor and the surface epithelium. Moreover, in seven cases (26%), multiple areas of continuity were exhibited between the tumor and the surface epithelium along a considerable surface area. In eight cases(30%), there was a band of connective tissue between the tumor and the surface epithelium, and in two cases, continuity could not be detected even after serial sectioning was performed. In regard to the histogenesis of PA, two major sources of origin must be considered. Those lesions that are located entirely within the connective tissue

Size (CfiG

Duration

I .o

NI

I.0

2 yr.

4.0

2 mo.

I.7

5 yr.

1.5

6 mo.

NI

NI

I .o

NI

I .2

6 mo.

0.8

6 mo.

0.5

2 yr.

NI

5 mo.

0.8

5 mo.

of the gingiva probably arise from remnants of the dental lamina (rests of Serres). The other lesions probably arise from the surface epithelium. The alternative hypothesis that the continuity between the tumor and the surface epithelium is fortuitous and simply represents fusion of the underlying tumor with the surface epithelium seemsunlikely because of its frequent appearance.6 Treatment

and follow-up

The treatment employed for PA in 31 cases was surgery, ranging from simple excision of the lesion to wide resection of the mandible with retention of the lower border. In 20 cases,just a simple excision was performed. Excision and curettage of the underlying bone was performed in five cases,and excision of the soft tissue and underlying alveolar bone was performed in three cases. In other cases,partial maxillectomy,‘2 en bloc resection of the mandible,15 and marginal mandibulectomy from the right canine to

Buchner and Sciubba

692

Oral Surf. June. 19X7

Table II. Published casesof peripheral ameloblastoma in extragingival locations ~-~~~a~--~--__r---T--T--r ’ .AjiC’ Author se.\ RUM Lowriorr h’0. I 7 3 4

Table Ill.

C‘flse n’o.

63

Braunstein ( 1949)” Klinar and McManis (1969)” Ramnarayan et al. (1985)j’ Woo et al. ( 1986)‘6

I C’f,,I

(

hrrariorr --

bl hl

w

6h

A

L. buccal R. buccal

mucosa mucos;~

3.0 5.0

3 \v!i. 3 mo

hi .-5’

M F

A .\

R. Hoor of mouth R. buccal mucosa

3.0 3.0

I mo. 9 mo.

Published casesof basal cell carcinoma in tooth-bearing areas 1 Author

Age

Sex

Raw*

60

M

W

74

M

W

47

M

u

I

Lawson

2

Williamson

3

Liroff

1

Peter5 et al. (1972)“’

72

F

NI

5

Peters et al. (1972)“’

55

F

w

6

Samit

11

M

W

et al. (1967)” et al. (1967)”

and Zeff (1972)”

(1978)”

the left premolarjs were performed. One widespread lesion was treated initially with cryosurgery, and the recurrent lesion was treated with radiotherapy.“’ Follow-up information, ranging from 6 months to 8 years after treatment, was available in 26 cases.In 21 cases, no recurrent lesions were observed. In five cases(19%), although the surgery was believed to be adequate, recurrent lesions occurred, respectively, after 2 months, 1.5 years, 5 years (two cases), and 7 years. These figures point to the importance and necessity of long-term follow-up for lesions diagnosed as PA. The intraosseous ameloblastoma has been characterized as having a marked tendency to recur. In the study by Small and Waldron,47 out of 352 cases followed postoperatively, there were 121 instances of recurrence (33%). Biologic

1----,si_L,---r-~--

behavior

While the intraosseous ameloblastoma is a locally aggressive neoplasm capable of invasive behavior

L. max. lateral incisor and canine L. mand. central and lateral incisors L. max. tuberosity area R. max. tuberosity area L. max. tuberositl area L. mand. retromolar and anterior tonsilfar area

and of destruction of bone and, thus, requires extensive surgical treatment, the PA does not manifest such behavior. It fails to invade bone, and conservative excision of the growth with adequate margins is the treatment of choice and is usually curative.6,“’ Careful pathologic examination of the margins of the excised tissue is important, and becauseexperience is limited, long-term follow-up is necessary. Extragingival

peripheral

ameloblastoma

There were four controversial extragingivai lesions that were reported under the term PA. Three of the lesions involved the buccal mucosa, and one of them involved the floor of the mouth. Although the strict definition of PA excludes lesions in extragingival locations, some authors, such as Patrikiou and coworkers23 and Shiba and colleagues,24included them in their reviews of PA. They argue that because of the histologic similarity to ameloblastoma, and with consideration given to the pluripotentiality of the oral epithelium, these lesions could be considered to be examples of PA. Meanwhile, other authors do

63 6

Peripheral

Table IV.

Published casesof peripheral adenomatoid odontogenic tumor

Volume Number

---

Chse

:vo. 1

Author

, Gorlin

and Chaudhry

2

\brams

et al. (1968)”

3

,\brams

et al. (1968)”

4 5

Abrams et al. ( 1968):’ Yazdi and Nowparast

Swinson 6 _____ NIL no informati
Table V.

--

epithelial

Six

-r,lr,,rr .Age

(1958)“’

( 1974)”

Loctrrionf

16

F

w

9

M

w

II

F

u

13 16

;

NI

F

NI

w

I6

(I 977)”

odontogenic tumors

[

1L‘U1I

Max. central and lateral incisors R. max. central incisor L. mitx. central incisor Mand. central incisors R. max. central and lateral incisors 1.. max. canine

-

693

r--;

Dtrratim

h1

3 >r.

NI

4 !r.

NI

NI

2.0 I .5

4 mo. I ,110.

I .5

2 yr.

--__

mnndiblc.

Published casesof peripheral calcifying epithelial odontogenic tumor

7

Author

Age 29 I6

6

Pindborg ( 1966)” Abrams and Howell ( I 967)“5 Decker and Laffitte (1967)‘” Patterson et al. (1969)“” Krolls and Pindborg (1974)6’ Wertheimer et al. ( I 977)62

7

Ai-ru

8

Ai-ru

9

Takeda

I 2 3 4 5

Rare*

Locationf

F F

W w

I .o 0.5

5 yr. NI

40

M

W

L. max. lateral incisor R. mand. central and lateral incisors L. mand. premolars

I.‘0

5 yr.

I2 60

M

B

FS

w

NI NI

I yr. Nl

20

M

W

1.5

NI

et al. (1982)“j

32

F

A

NI

IO \r.

et al. (1982)“?

47

F

A

NI

1 5”.

31

F

A

Mand. central incisors Anterior portion of mand. R. max. canine and first premolar L. mand. premolars and first molar R. mand. canine and first premolar R. max. molar region

I.7

NI

et al. ( 1983)hJ

-~ Sex

NILno iniormatton *W--white: B-~-blat k: A --Asian. tmau.--maxilla: mud.--mandible t.4, of Franklin and Pindborg.”

not accept the diagnosis of PA for these lesions. Wesley and colleagues’8 and Moskow and Baden believe that these lesions represent tumors of salivary gland origin with histopathologic resemblance to an ameloblastoma. PERIPHERAL TUMOR

ADENOMATOID

ODONTOGENIC

A review of the literature by Giansanti and coworkers48in 1970 revealed more than 100 casesof intraosseous adenomatoid odontogenic tumors (AOT), and a second review by Courtney and Kerr49 in 1975 raised the number to almost 150 cases. Occurrence of the lesions within soft tissues is rare; we were able to find only six acceptable, welldocumented cases.5@”We have excluded a case

reported by Ishikawa and Mori5” because we could not determine the location of the lesion. We could also not include three peripheral lesions that were reported by Courtney and KerrJ9 because they were analyzed together with the intraosseous lesions. The only information that is available on these three lesions is that they appeared as gingival swellings in the region of the maxillary central incisors. Table IV summarizes the data of the six acceptable cases of peripheral AOT. Age and gender

distribution

The ages ranged from 9 to 16 years, with a mean of 13.5 years. According to the review by Courtney and Kerr,49 the age range of the patients with intraosseous lesions was 5 to 53 years with a mean of

694

Buchner and Sciubba

17.9 years. Thus, the six patients with peripheral lesions exhibited a lower mean age than patients with intraosseous lesions. Of the six peripheral cases,five occurred in female patients and one in a male patient. The gender distribution of the intraosseous lesions also showed a marked predilection for occurrence in females (64%). Location

The peripheral lesions primarily occur in the maxillary arch (83%). They are located, on both the mandible and the maxilla, in the incisor and canine areas. No lesions have been observed distal to the canine region. The intraosseous lesions also have a predilection for the maxilla, forming 65% of the total, while 35% were noted in the mandible. Most of the lesions occurred in the anterior portion of the mandible and the maxilla with 76% developing in the incisor and canine area. Clinical

features

All of the peripheral lesions were evident clinically as painless gingival swellings. In one case,52the lesion produced protrusion of the teeth; in another case, there was a history of a blow to the chin that occurred during a fall and, shortly thereafter, a mass developed.5’The duration of the lesions ranged from 1 month to 7 years. The preoperative diagnoses included fibroma, gingival hyperplasia, and fibrous epulis. Bony depression immediately beneath the lesion was reported in one case, and in another case the radiologic appearance suggested superficial erosion of the underlying bone. Histologic

features

and hlstogenesis

The histomorphologic features of the peripheral AOT are similar to those observed in the central lesions. Also, like the intraosseous lesion, they are usually solid, Unlike the intraosseous lesion, however, they are generally unencapsulated, although in one cases3the lesion was surrounded by a relatively thick capsule. In regard to the histogenesis of the peripheral AOT, Abrams and coworkers5’ suggested that their three caseswere associatedwith unerupted teeth. As normal eruption progressed, they speculated, the tumor was pushed peripherally and to the side, and only those portions that were not destroyed by the erupting tooth remained as a residual AOT. Yazdi and Nowparast,52on the other hand, suggested that the basal cell layer of the surface epithelium is the source of origin of the peripheral AOT.

Oral Surg. June. 19X7

Treatment

and follow-up

The lesions were treated by means of surgical excision. In one case,j’ a “small deficiency in bone” was noted at surgery, and the surgeon performed bony curettage and extracted the underlying tooth. Follow-up histories were available in three cases for 2, 12, and 25 years, respectively. No recurrences were reported. The intraosseous AOT is a benign lesion that requires only conservative surgical excision. There is no indication that the lesion recurs.” PERIPHERAL CALCIFYING ODONTOGENIC TUMOR

EPITHELIAL

The vast majority of the calcifying epithelial odontogenic tumors (CEOT) are central lesions within the maxilla and the mandible. A review by Franklin and Pindborg5’ in 1976 reported that 108 intraosseous lesions have been described since Pindborg’s original article in 1955? Occurrence of the lesion in soft tissues is rare; we were able to find only nine acceptable, well-documented casesin the literature.57-oJ We have excluded the casereported by Cole and Jones? involving the upper lip since Franklin and Pindborg5’ claimed that this lesion was actually a monomorphic adenoma of salivary gland origin. We have also excluded the case reported by Blank and colleagues,66who described a microscopic focus of CEOT within an operculum associated with an unerupted tooth. Wertheimer and coworkersbZ included in their review of the extraosseousCEOT a case reported by Greer and Richardson.@ It is our belief that this was actually an intraosseous lesion, since the authors stated in their article that it was “located entirely within bone.” Shiba and associatesZJalso classified the caseof Greer and Richardson erroneously as an example of extraosseous CEOT. Table V summarizes the data of the nine acceptable cases. Age and gender

distribution

The age range of the nine patients with peripheral CEOT was from 12 to 60 years. The mean age at the time of initial diagnosis was 3 1.8 years. According to the review by Franklin and Pindborg,ssthe age range for the patients with intraosseous lesions was 8 to 92 years, with a mean age of 40.4 years. Thus, the nine patients with peripheral lesions exhibited a noticeably lower mean age than those with the intraosseous lesions. Of the nine peripheral cases, six involved female patients and three involved male patients. A nearly equal distribution of the intraosseous lesions was noted between male and female patients.sj

Volume Number

Peripheral

63 6

Location

There is a predilection of peripheral lesions for the mandibular arch (66.6%). All of the mandibular lesions and most of those on the maxilla occur in the incisor and canine-premolar region. Only a single case of a peripheral lesion has been described in the molar region of the maxilla. The intraosseous lesions are found primarily in the mandible but, in contrast to the peripheral lesions, are mainly located in the molar region. Clinical

features

Clinically, the peripheral lesions appear most commonly as painless, firm gingival masses.In two cases, the color of the lesion was slightly red, and in one case, the surface was ulcerated. The duration of the lesions ranged from 1 to 10 years. The preoperative diagnoses included fibroma, peripheral fibroma with calcification, peripheral giant cell granuloma, and “epulis.” An underlying bony depression or saucerization was reported in four cases. In an additional case, there was a radiographic appearance of superficial bony erosion. Histologic

features

and histogenesis

The histomorphologic pattern of intraosseous CEOT is variable with a clear cell variant now being well recognized. Histomorphologically, the peripheral lesions are identical to their intraosseous counterparts. It was interesting to note that of the nine peripheral lesions, four exhibited a predominant clear cell component.58,62,63 In regard to the histogenesis of the intraosseous CEOT, most investigators currently believe that it originates in the stratum intermedium of the enamel organ. The peripheral location further suggests the possibility that it arises from rests of the dental lamina, which are located in the gingiva, or from the basal cells of the surface epithelium. In two cases,a connection between the tumor and the mucosal epithelium was noted.62*64 Treatment

and follow-up

Five lesions were treated by means of simple excision, and in an additional case, the lesion was excised with the use of electrocautery and the underlying bone was cauterized. In one case, surgical excision of the underlying bone was performed,64and in an additional case,63a “partial mandibular resection” was done. Follow-up information, which ranged from 2 years to 10 years after treatment, was available for only three cases. No recurrences of these lesions have been recorded.

epithelial

odontogenic tumors

695

The intraosseous CEOT is considered to be locally invasive, although it does not seemto extend into the intertrabecular spacesas readily as does the ameloblastoma.6’ The recurrence rate has been reported to be 14%.55 PERIPHERAL

SQUAMOUS

ODONTOGENIC

TUMOR

The squamous odontogenic tumor (SOT) was first described by Pullon and associates68in 1975. Twenty-two casesof intraosseous SOT had been reported in the literature through the end of 1985. A single case of peripheral SOT was reported in 1985 by Hietanen and coworkers.69The lesion occurred in an 1l-year-old girl as a nodule in the palatal mucosa in the region of the right maxillary canine and first premolar. The lesion was excised and recurred 13 years later in the same location. Radiologic examination did not show bony involvement, and at surgery the lesion appeared entirely extraosseous.The histologic features of the recurrent lesion were similar to those of the primary tumor, and it was diagnosed as a recurrent peripheral SOT. DISCUSSION

Peripheral (extraosseous or soft tissue) epithelial odontogenic tumors (PEOT) are rare lesions that occur in the soft tissue overlying tooth-bearing regions of the mandible and the maxilla. A review of the English-language literature revealed only 48 acceptable, well-documented cases.Thirty-two cases involved PA (26 cases reported as PA and 6 cases reported as basal cell carcinoma of the gingiva); 6 involved peripheral AOT; 9 involved peripheral CEOT; and one involved a peripheral SOT. An additional four caseswere reported as PA in extragingival locations (the buccal mucosa and the floor of the mouth), but the odontogenic origin of the lesions is debatable and the cases thus were not included in our analysis. A single case report by Vuletin and coworkers70 was also not included becausewe were unable to categorize the lesion into the groups that we have described and because no other examples of such were noted. With respect to the histogenesis of PEOT, we believe that it may arise from either the basal cell layer of the surface epithelium of the gingiva or the remnants of the dental lamina (rests of Serres), located within the gingiva. Because of the rare occurrence and the limited number of case reports (especially with the limited follow-up), it is difficult to draw a firm conclusion with respect to the clinical and the biologic behavior of the PEOT. Some conclusions, however, can be

696 Buchner and Sciubba drawn from the 32 cases in which tumors were diagnosed as PA. Although the histology of the PA is similar or even identical to that of its central (intraosseous) counterpart, it differs in its clinical features and in its biologic behavior. The PA differs from its intraosseouscounterpart in the following ways: (1) it occurs later in life (in the fifth and sixth decades), (2) it is most commonly located in the mandibular lingual gingiva of the canine-premolar area, (3) it does not exhibit an aggressive, destructive behavior, nor does it invade the underlying bone, and (4) it is treated conservatively by means of local excision with minimal but adequate margins. It is of the utmost importance for oral pathologists and oral surgeons to understand that the PA exhibits a different biologic behavior than doesits central counterpart, in order to avoid unnecessaryextensive, sometimes mutilating surgery as has been performed in some cases.‘2,‘“,38The rather benign nature of the PA brings into question whether it is truly analogous to the central ameloblastoma. The benign biologic behavior of the PA appearsto also hold true for the lesionsdiagnosedas peripheral CEOT and undoubtedly holds true for the peripheral AOT. One additional point deserves special attention. Follow-up information in the reported cases is quite limited, and long-term follow-up is rare. In order to enhance our knowledge with respect to the biologic behavior of PEOT, the observance of these patients over a long period of time is necessary. We extend thanks to Professor Leo M. Sreebny of the State University of New York at Stony Brook for his assistance and criticism in the preparation of this article.

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15.

Reprint requests IO: Dr. James J. Sciubba Department of Dentistry Long Island Jewish-Hillside Medical Center New Hyde Park, NY I 1042