Journal of Interdisciplinary Dentistry

: 2015  |  Volume : 5  |  Issue : 1  |  Page : 37--40

Unicystic ameloblastoma with impacted third molar mimicking dentigerous cyst

BL Laxmidevi1, Masroor Mohammed2, KR Ashok Kumar3,  
1 Department of Oral Pathology and Microbiology, Sri Siddhartha Dental College and Hospital, B. H. Road, Agalakote, Tumkur, India
2 Private Dental Practitioner, Bangalore, Karnataka, India
3 Department of Oral Surgery, Sri Siddhartha Dental College and Hospital, B. H. Road, Agalakote, Tumkur, India

Correspondence Address:
B L Laxmidevi
Department of Oral Pathology and Microbiology, Sri Siddhartha Dental College and Hospital, B. H. Road, Agalakote, Tumkur


Unicystic ameloblastoma (UA) derived the name by its macro and microscopic appearance. It is considered to be less aggressive compared with conventional ameloblastoma both in its growth pattern and recurrence rate, however, few of its histopathological types are treated in the same manner as that of conventional ameloblastoma. Therefore, the aggressiveness of this lesion is a dependent factor. Most of these lesions when occur in the mandibular third molar region with impaction, they are usually removed on radiographic diagnosis of dentigerous cyst and then the specimen is subjected to histopathological examination. Hence, the diagnosis of UA is evident only after microscopic evaluation of the specimen. Here, we report one such case of UA treated by enucleating on radiological findings. Clinical Relevance to Interdisciplinary Dentistry
  • When a cyst of the jaw is associated with impacted tooth the most common provisional diagnosis is dentigerous cyst, at the same time unicystic ameloblastoma (UA) (dentigerous variant) need to be considered as one of the differential diagnosis along with other cysts of the jaws. Then, it becomes important for the radiologist to carefully examine radiograph to assess the true dentigerous cyst-impacted tooth relationship to narrow down the diagnosis
  • On removal of such cyst either in toto or as a cyst wall curettage, it is important for the surgeon and the pathologist to examine both the inner and outer wall of the cyst sac. The presence of several polypoid/exophytic/nodular growths in the inner and/outer surface of the cyst wall may favor the initial diagnosis of UA rather than dentigerous cyst even though lack of these finding does not contradict the diagnosis of UA
  • When treatment of such cyst done based on radiographic diagnosis, entire tissue of the cyst after enucleation must be evaluated histopathologically by the pathologist to eliminate possibility of UA and when diagnosed histopathologically as UA, serial sectioning of the entire tissue is mandatory for the pathologist to arrive at the diagnosis of proper subtype of UA, as the recurrence rate changes accordingly
  • In our case, the UA was treated conservatively by considering the radiographic diagnosis of a dentigerous cyst. Whereas histopathology revealed UA subtype 1.2.3. Follow-up after 6 months showed good bone remodeling with no sign of recurrence on the radiograph. Since the recurrence of UA is long delayed, regular follow-up for a long period is necessary
  • Thus, the collective opinion by the clinician, radiologist, surgeon, and pathologist plays a very important role in the effective management of UAs.

How to cite this article:
Laxmidevi B L, Mohammed M, Ashok Kumar K R. Unicystic ameloblastoma with impacted third molar mimicking dentigerous cyst.J Interdiscip Dentistry 2015;5:37-40

How to cite this URL:
Laxmidevi B L, Mohammed M, Ashok Kumar K R. Unicystic ameloblastoma with impacted third molar mimicking dentigerous cyst. J Interdiscip Dentistry [serial online] 2015 [cited 2020 Oct 21 ];5:37-40
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Full Text


Literature says, around 1% of all oral tumors are odontogenic and 7-12% are diagnosed as odontogenic cysts in all oral maxillofacial biopsies. [1],[2]

Ameloblastoma being the common odontogenic tumor exhibits subtypes among which Unicystic ameloblastoma (UA) comprise around 5-22%. The dilemma in the diagnosis of UA exists on a radiograph, when it is associated impacted third molar where it exclusively shows similarity to the dentigerous cyst and most of them were enucleated on that basis. [1],[3] Thus, the diagnosis of UA becomes evident only when the entire specimen was evaluated histopathologically. [3]

Here, we report one such case in 21-year-old boy, radiographically mimicking dentigerous cyst with the impacted third molar, which was treated conservatively.


A 21-year-old boy reported the private clinic with a complaint of discharge in the lower right back region since 1-week. Extraoral examination did not reveal any gross swelling or facial asymmetry. Intraoral examination showed missing lower right third molar with all the other molars erupted into the oral cavity. Oral mucosa in that region was slightly inflamed with a purulent discharge. Suspecting the pathology associated with missing tooth the panoramic radiograph was taken, that revealed huge unilocular radiolucent area extending from mesial root of the impacted third molar to coronoid notch involving the whole ramus of the mandible on right side, with well-defined margins [Figure 1]. Radiographically, it was diagnosed as a dentigerous cyst of circumferential type and was enucleated completely along with the extraction of the impacted third molar. The entire specimen was subjected for the histopathological examination.{Figure 1}

Microscopic examination showed the cystic lining lined by ameloblastomatous epithelium overlying with stellate reticulum like cells [Figure 2]. Proliferation of this ameloblastomatous epithelium is seen both in the lumen [Figure 3] and as well as in the connective tissue capsule of the cyst [Figure 4]. Thus, the diagnosis of UA subtype 1.2.3 was made.{Figure 2}{Figure 3}{Figure 4}

Follow-up after 1-week showed satisfactory healing, at the same time the patient was informed about the diagnosis and asked for regular follow-up at many intervals, which is mandatory, since the UA subtype 1.2.3, has a greater tendency for recurrence compared to first two subgroups according to Reichart and Philipsen. Root canal treatment for the second molar was scheduled which was nonvital during the follow-up.

During the recall after 6 months, the radiograph was taken that revealed a satisfactory bone formation with no evidence of recurrence [Figure 5]. The patient was again informed for checkups at regular period intervals since the recurrence of UAs is long delayed and the same was also informed to his guardian.{Figure 5}{Figure 6}


According to the various theories, UAs may arise from reduced enamel epithelium associated with the developing tooth/ameloblastoma may develop in preexisting dentigerous cyst or other types of odontogenic cyst/solid ameloblastoma may undergo cystic degeneration leading to UA. However, satisfactory evidence to prove these theories is difficult to produce. Whereas few authors say, UAs are de novo cystic neoplasms. [1]

Though the lesion presents as local asymptomatic swelling with facial asymmetry, pain, and signs of lip numbness are rare, while the discharge or drainage is seen in only when it is secondarily infected, [1],[4] as in our case the patient consulted due to discharge in the lower right third molar area along with missing tooth.

Various radiographic patterns of UA can be seen, such as pericoronal unilocular, extensive pericoronal unilocular, pericoronal scalloped, and periapical unilocular, inter-radicular and even multilocular [Figure 6], but with a clear preponderance for the unilocular pattern. [3] Pericoronal unilocular type of UA with the impacted third molar, exclusively shows similarity to a dentigerous cyst. Hence, it is categorized as dentigerous variant (with impacted tooth). [1] In most of these cases, radiographic diagnosis of dentigerous cyst was made considering the age and the lesion was surgically removed and whole tissue was subjected to histopathological diagnosis. It is, therefore, suggested that, because the diagnosis of UA is made in a postoperative step by a careful histopathological examination of more serial sections and because incisional biopsy may not be able to reflect the true nature of the lesion, so to have proper diagnosis entire tissue must be included for histopathological examination. [3] In our case also the lesion was enucleated by making the radiographic diagnosis of dentigerous cyst and the entire tissue was subjected for the histopathological diagnosis.

Macroscopically, UAs reveal several intraluminal and/intramural focal thickening nodules, but absence of these does not contradict the diagnosis of UA. Microscopy of UAs shows the cystic lining with the basal ameloblasts like cells and stellate reticulum like cells above. Ameloblastomatous proliferation in the lumen of cystic cavity is termed as luminal and the same proliferation in the connective tissue as intramural, which is considered to be aggressive compared to any other variant. However, a combination of these two also exist posing the same aggressiveness. [1],[5] Based on this ameloblastomatous proliferation, the treatment of UA continues to be controversial. Influencing factors are, the age, clinicoradiographic variant, anatomic locations and clinical behavior of the lesion and finally the histopathological variant. Available treatment options are enucleation, enucleation followed by use of Carnoy's solution, marsupialization followed by enucleation, marginal resection, and aggressive resection. [4]

Intramural variant shows highest recurrence (35.7%) with an average interval of 7 years between initial treatment and recurrence. [6],[7] Hence, whatever may be the surgical approach the surgeon decides to take, long-term follow-up is mandatory, as recurrence of UA may be long delayed. [8]

In our case, even though the lesion was treated conservatively it showed good bone remodeling after 6 months of treatment without any evidence of recurrence. Hence, dilemma regarding treatment options for UA still exists, but nevertheless for the UA whichever may be the histopathological type, clinical and radiographic follow-up for up to 10 years is mandatory, with initial follow-up of 6 months for 2 years, and then after annually, to exclude the risk of late recurrence and same were explained to the patient and her/his guardian, which is followed in our case.


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