INTRODUCTION

eripheral ameloblastoma (PA) is uncommonsubtype of ameloblastoma. In fact it is the rarestvariant, which accounts for about 1 to 10% of

all ameloblastomas.1 In contrast to the intraosseous locallyaggressive ameloblastoma, PA is soft tissue tumor withindolent biological behavior.2,3 It has been theorized thatthis tumor may arise from remnants of dental laminabeneath the oral mucosa or from the basal cells of theoral epithelium.4,5 PA tends to occur between the 5th and7th decades of life with an average reported age of 52years.2 Clinically, PA is usually a painless lesion thatcommonly affects the mandibular gingiva.6 Because PAhas non-specific clinical presentation, it is mostlyconsidered as pyogenic granuloma or fibroma6. We reporta case of PA that was observed in a 32-year-old manpresenting with a gingival swelling in the lingualmandibular premolar area.

CASE REPORT

A 32-year-old Indian heavy-smoker manpresented tothe oral surgery clinic with painless gingival swelling onthe left side of the mandible. The lesion was asymptomatic

and had been noticed by the patient two years ago beforethe consultation. Intra-oral examination showed a sessilepink to red in color gingival mass and was located on thelingual gingiva between the left mandibular 2nd premolarand 1st molar (Fig. 1). The lesion was firm with granular

surface. Orthopantomogram (OPG) was taken and showedno remarkable changes (Fig. 2). Clinically, the diagnosiswas pyogenic granuloma based on the clinical presentation. Under local anesthesia, the lesion was surgicallyexcised with 1 mm safe margin, formalin-fixed and sentfor histopathologic examination. Grossly, the excisedspecimen was a whitish-brown, firm soft tissue massmeasured 1.3 cm x 0.7 cm x 0.3 cm. Microscopically, theexamination showed multicentric down-growth and

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PERIPHERAL AMELOBLASTOMA PRESENTING AS APYOGENIC GRANULOMA: A CASE REPORT WITH ANIMMUNOHISTOCHEMICAL STUDY

ABSTRACT: Peripheral ameloblastoma is rare tumor occurring on extraosseous location. It accounts for about 1to 10% of all ameloblastomas. A 32-year-old Indian heavy smoker, presented to the oral surgery clinic with painlessgingival swelling on the left side of the mandible. Radiological examination did not reveal any bone involvement.A histologic exam showed islands of odontogenic epithelium that were seen to bein continuity with surface epithelium.The tumor islands exhibited the typical features of ameloblastoma with follicular arrangements. In addition, thetumor was positive for CK19 and negative for Ber-Ep4. Five percent of the tumor cells showed positivity for Ki-67. The final diagnosis was peripheral ameloblastoma, which is a rare variant of ameloblastoma. It is emphasizedto consider peripheral ameloblastoma among the differential diagnosis of gingival swellings.KEY WORDS: Peripheral ameloblastoma, ameloblastoma, gingiva, immunohistochemistry, odontogenic tumor .HOW TO CITE: AlQahtani D. Peripheral ameloblastoma presenting as a pyogenic granuloma: A case report withan immunohisto chemical study. J Pak Dent Assoc 2015; 24(3):152-155.Received: September 15 2015, Accepted: October 26, 2015

1. Department of Oral Medicine and Diagnostic Sciences (DDS), College of Dentistry,King Saud University, Riyadh, Saudi ArabiaCorresponding author: “Dr Dalal ALQahtani” < dalalq@ksu.edu.sa >

Dalal AL Qahtani BDS, MSc, M Ed

CASE REPORT

P

Figure 1: Intra-oral picture of gingival mass on the leftmandibular premolar-molar area.

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budding of the basal layer of the surface epitheliumwithsome tumor cells were observed lying free in theconnective tissue stroma (Fig. 3). Most of the proliferatingislands exhibited peripheral rows of palisadedcolumnarcells that showed reverse polarization and

hyperchromatism with infrequent mitosis. The majorpattern of the proliferating nests is follicular with someareas showing acanthomatous and cystic changes(Fig. 4). In the lumen of some of the cystic areas neutrophilinfiltrate was seen. No cell atypia or pleomorphism wasnoted. The connective tissue stroma was collagenous andmildly infiltrated by chronic inflammatory cells. Additionalimmunohistochemical studies for CK19, Ber-Ep4 andKi-67 were ordered. The tumor islands were partiallypositive for CK19 with marked reaction in theirluminalareas (Fig. 5), and negative for Ber-Ep4. Ki-67was positive in 5% of the cells, which were foundmainly in the in the basal/parabasal layers of the epithelialislands (Fig. 6). Based on the clinical, histopathology andimmunohistochemistry results, the lesion was finally diagnosed as peripheral ameloblastoma.

Peripheral ameloblastoma presenting as a pyogenic granulomaAlQahtani D

Figure 2: Orthopantomogram (OPG) of the case showing noremarkable changes.

Figure 3: A low-power view of tumor cells arranged in islandswithin a fibrous stroma exhibiting multicentric connections

with the surface epithelium (haematoxylin and eosin (H & E).

Figure 4: Ameloblastoma islands in follicular arrangementsshowing palisading nuclei of the peripheral cells

(H and E, original magnification ×10).

Figure 5: Tumor cells showing positivity for CK19(immunhistochmistery (IHC), original magnification ×4).

Figure 6: Tumor cells showing 5% positivity for Ki-67 in the in the basal/parabasal layers

(IHC, original magnification ×20).

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DISCUSSION

Odontogenic tumors are uncommon unique lesionsof the jaw bones. They comprise a heterogeneous groupof lesions that is derived from epithelium orectomesenchym, or both.7 Though these lesions share thecommon origin from the tooth-forming apparatus, theypossess diverse histopathologic forms and clinicalbehavior. Some of these lesions represent a true neoplasticwhile others are a tumor-like hamartomatous lesions.8

PA is a rare soft tissue odontogenic tumor that wasfirst described in the literature by Kuru in 1911.9 In 2005,the World Health Organization (WHO) classified PAasone of the distinctive subtypes of ameloblastoma.1 Thisis because of its extraosseous location and less aggressiveclinical behavior compared with the conventionalameloblastoma.10 Although PA is rare, it is the 2nd mostcommon peripheral odontogenic tumor (28% of cases),preceded by odontogenic fibroma.11 Similar to theconventional ameloblastoma and other odontogenictumors, the etiopathogenesis of PA is poorly understoodand the origin is still unclear. Nevertheless, hypotheseshave been suggested that it could originate from theepithelial rests of dental lamina or from the basal layerof the oral epithelium.4,5 In fact, many of the reportedcases of PA (one of them is our case) were described tobe in connection with surface epithelium suggesting PAmight be derived from the surface epithelial layer.12,13 Onthe other hand, other cases were reported to be completelyin the connective tissue without contact with surfaceepithelium suggesting that it might be to be derived fromdental lamina residuals.2,5,14 Genetically, one study reportedgenetic aberration in chromosome 7 (trisomy) in PAwhichmay play a role in its tumorigenesis.15

PA is typically presented as slowly growing painlessmass with smooth surface. It is more in males than femalesby ratio of 1.9:1, and frequently occurs on the middle ageof life with mean age of 52 years.2 In regard to the location,it is most commonly found on the mandibular premolarregion with percentage of 33%.2 Our reported casepresented most of these clinical characteristics: A malepatient with gingival swelling on the premolar-molararea. However, the patient here is 32 years old, whichconsidered younger than the reported mean age of PA.

In PA, the step of detailed radiological investigationis essential to rule out any bone involvement and themisdiagnosis of central ameloblastoma. In the currentcase, radiological exam didn't indicate any bone

involvement, which directed the diagnosis towardperipheral lesions.

Although PA is rare extraosseous tumor, the clinicaldiagnosis of gingival swellings should involve PA asdifferential diagnosis since it resembles clinically othergingival swellings including pyogenic granuloma,traumatic fibroma, peripheral odontogenic fibroma,peripheral giant cell granuloma, and peripheral ossifyingfibroma.2 Those lesions could be excluded based on thehistopathlogical examination.

Under microscope, PA should be differentiatedfromperipheral squamous odontogenic tumor, peripheralodontogenic fibroma and oral basal cell carcinoma1,2,16.The present case showed the typical features ofameloblastoma with islands exhibiting follicular andacanthomatous patterns. It has been shown that those twopatterns are the most common in PA.2 Occurrence ofcalcifications in PA is not common finding, although itwas reported recently in one case.11

Currently, the role of immunohistochemistry is limitedin diagnosing odontogenic tumors as these tumor typesare largely identified by their morphologic features.However, some markers can be used to help indistinguishing the odontogenictumors from non-odontogenicones. For this purpose, it has been shownthat CK19 and Ber-Ep4 can be usedto differentiate betweenPA and basal cell carcinoma16. Our case showed diffusepositivity for CK19 and negativity for Ber-Ep4 confirmingthe diagnosis of PA.In addition, the positive reaction ofPA neoplastic cells to CK19 indicates that PA is mostlikely to originatefrom remnants of odontogenic epithlium5.The present case also showed low proliferating activity(Ki-67=5%) which indicates low-level ofaggressivenessof this tumor compared with intraosseous ameloblastomathat was shown to have greater expression of theproliferative markers.5,17 In fact, the labeling index of Ki-67 has been linked to the patient's age, the gross appearanceof the excised specimen (solid, mixed, cystic), generalhistological patterns and the cytological pattern of theouter layer cells of ameloblastoma.17

Because of the indolent biological behavior of PA, ithas been recommended that this tumor can be treatedconservatively by local excision with small free margin.2,10

Up to date, there is no reported cases of malignanttransformation of PA, although some cases have beenpublished in regard to PA with malignancy.2,18 Therecurrence rate is low, and close follow up is advised,especially for PA with atypical features.10

Peripheral ameloblastoma presenting as a pyogenic granulomaAlQahtani D

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CONCLUSION

We have reported a case of peripheral ameloblastomain the gingival region because of its low incidence andthe need to include this lesion on the differentialdiagnosis of swellings affecting the gingiva.

Author Contribution: DAQ collected the clinical andhistopathological data, drafted, review and finalizedthe paper.Disclosure: Author declares no conflict of interest inany form.

REFERENCES

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8. Tjioe Kellen Cristine, Damante José Humberto,Oliveira Denise Tostes. The Onset of a PeripheralAmeloblastoma. Case Rep Oncol Med 2012;2012(c):1-4.9. H. Kuru. Ueber das adamantinoma. Zentralbl AllgPathol 1911;22:291.10. Renu Yadav, Anubha Gulati, Rahul Sharma SatyaNarain. Peripheral Ameloblastoma: Review of Literatureand Case Presentation Ind J Multidisciplinary Dent2011;1:135-139.11. Alexandre Nelise, Sedassari Bruno Tavares, DeFábio. Peripheral Ameloblastoma with DystrophicCalcification: An Unusual Feature in Non- CalcifyingOdontogenic Tumors Braz Dent J 2014;25:253-256.12. Ide Fumio, Mishima Kenji, Miyazaki Yuji, SaitoIchiro, Kusama Kaoru. Peripheral ameloblastoma in-situ: an evidential fact of surface epithelium origin.Oral Surgery, Oral Med Oral Pathol Oral RadiolEndodontology 2009;108:763-767.13. Ide F. Peripheral ameloblastoma of the buccalmucosa. Oral Surg Oral Med Oral Pathol Oral RadiolEndod 2010;109:653-4; author reply 654-655.14. Vanoven Bryan J, Parker Noah P, Petruzzelli GuyJ. Peripheral ameloblastoma of the maxilla: a case reportand literature review. Am J Otolaryngol - Head NeckMed Surg 2008;29:357-360.15. Manor Esther, Delgado Bertha, Joshua Ben Zion,Brennan Peter A, Bodner Lipa. Trisomy 7 as soleaberration in peripheral ameloblastoma of the mandible.J Oral Maxil lofac Surg 2013;71:1217-1219.16. Lentini M, Simone a, Carrozza G. Peripheralameloblastoma: Use of cytokeratin 19 and Ber-EP4 todistinguish it from basal cell carcinoma. Oral OncolExtra 2004;40:79-80.17. Sandra F, Mitsuyasu T, Nakamura N, ShiratsuchiY, Ohishi M. Immunohistochemical evaluation of PCNAand Ki-67 in ameloblastoma. Oral Oncol 2001;37:193-198.18. Califano L, Maremonti P, Boscaino A, De Rosa G,Giardino C. Peripheral ameloblastoma: report of a casewith malignant aspect. Br J Oral Maxillofac Surg1996;34:240-242.

Peripheral ameloblastoma presenting as a pyogenic granulomaAlQahtani D