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 Table of Contents  
Year : 2017  |  Volume : 7  |  Issue : 2  |  Page : 135-139

Unusual cystic lesion in mandibular midline: A diagnostic dilemma

Department of Oral Medicine and Radiology, Swami Devi Dyal Hospital and Dental College, Panchkula, Haryana, India

Date of Web Publication28-Dec-2017

Correspondence Address:
Dr. Aravinda Konidena
Department of Oral Medicine and Radiology, Swami Devi Dyal Hospital and Dental College, Golpura, Panchkula, Haryana
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/ijmd.ijmd_6_17

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Odontogenic neoplasms present with characteristic clinicoradiological presentation giving clue to their diagnosis. However, unusual presentations may confuse the clinician and diagnosis may become elusive. We encountered one such atypical presentation when a 60-year-old female presented with an unusually large cystic lesion in the mandibular midline, creating a diagnostic dilemma. Unicystic ameloblastoma (UA) presents with clinical and radiographic features of a jaw cyst but show a typical ameloblastomatous transformation of lining epithelium, with or without luminal and/or mural tumor proliferation on histologic examination. This variant differs from solid ameloblastoma in being less aggressive and being seen commonly in young individuals. Another unique fact about UA is that recurrence may be long delayed, and a long-term postoperative follow-up is essential for proper management of these patients.

Keywords: Ameloblastoma; jaw tumor; unicystic ameloblastoma; unilocular radiolucency

How to cite this article:
Konidena A, Shekhar S, Dixit A, Patil DJ. Unusual cystic lesion in mandibular midline: A diagnostic dilemma. Indian J Multidiscip Dent 2017;7:135-9

How to cite this URL:
Konidena A, Shekhar S, Dixit A, Patil DJ. Unusual cystic lesion in mandibular midline: A diagnostic dilemma. Indian J Multidiscip Dent [serial online] 2017 [cited 2020 Dec 4];7:135-9. Available from: https://www.ijmdent.com/text.asp?2017/7/2/135/221772

  Introduction Top

Most of the jaw tumors have certain characteristic clinicoradiological features that point toward the diagnosis. Diagnosis becomes elusive when they present in an unconventional manner, thus posing a challenge to the clinician. The most common tumor of odontogenic origin is ameloblastoma, which develops from epithelial cellular elements and dental tissues in various phases of development.[1] The concept of this tumor was introduced by Robinson and Martinez in 1977 who described it as “unicentric, nonfunctional, intermittent in growth, anatomically benign, and clinically persistent.”[2]

Clinicoradiologically, ameloblastomas had been classified as extraosseous/peripheral (1%) and intraosseous (unicystic 5% or multicystic/solid 94%).[3],[4] Among the intraosseous variants of ameloblastoma, unicystic ameloblastoma (UA) also named as cystogenic ameloblastoma by the WHO is a less frequent growth pattern.[5] The term “unicystic” is derived from its macro- and micro-scopic appearance of a cavity lined by odontogenic epithelium.[6] However, unlike the solid variant, UA is seen to occur in a younger age group, with the age group of 16–20 years being most commonly involved.[7]

Fifty to eighty percent of UA cases are associated with tooth impaction, the mandibular third molar being most often involved. It is thought to arise either from preexisting dentigerous cyst (dentigerous variant) or de novo (nondentigerous variant).[8] They rarely present in patients over 40 years of age. On the contrary, we encountered a case of UA in the mandibular anterior region in a 60-year-old female patient, hence reporting it.

  Case Report Top

A 60-year-old female presented to us complaining of pain and swelling in the lower right back tooth region for 2–3 days. Pain was severe, sharp, throbbing, and continuous localized to a lower back loose tooth. Along with pain, swelling was noticed by the patient 2–3 days back in the present size only and it was not associated with paresthesia or numbness of the lower lip. Pus discharge and fever were not reported. Past medical and family history was noncontributory. Past dental history revealed extractions of the lower front teeth due to mobility 2–3 years back. The patient was moderately built, moderately nourished, and well oriented to time, place, and person. No signs of anemia, icterus, and clubbing, cyanosis, or pedal edema were found. All vital signs were within normal limits.

Extraorally, the swelling was only slightly apparent and caused very slight visible facial asymmetry. There were bilateral single, mobile, firm, nontender, submandibular lymph nodes palpable. On intraoral examination, attached gingiva of 46 was erythematous, enlarged with pus discharge from the periodontal pocket, and was associated with Grade III mobility of 46, suggestive of a periodontal abscess.

On routine intraoral examination, we incidentally also found an obliteration of the anterior mandibular labial vestibule with a smooth expansion of buccal cortex and missing mandibular anteriors [Figure 1]. The swelling was 3 cm in size extending from 43 to 35 anteroposteriorly crossing the midline and from the crest of alveolar ridge to the depth of vestibule superoinferiorly. No visible pulsations or pus discharge was seen though the overlying mucosa was slightly erythematous. The lesion was bony hard in consistency, slightly tender, nonfluctuant except for cystic consistency on superior aspect. Pus discharge was noted from gingival sulcus of 34 on digital pressure. There was Grade III mobility with 34 and Grade II mobility with 44. A provisional diagnosis of infected residual cyst was given, and various lesions were considered under differential diagnosis as discussed in [Table 1].
Figure 1: An obliteration of the anterior mandibular labial vestibule with a smooth expansion of buccal cortex and missing mandibular anteriors

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Table 1: Differential diagnosis of the present case based on clinical features

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Aspiration was done with a 24-gauge needle which resulted in 0.5 ml of straw-colored, thin, light yellow fluid [Figure 2]. The biochemical analysis of the aspirate revealed 11.2 g/dl soluble protein content, indicating nonkeratinizing infected cyst. A mandibular cross-sectional occlusal radiograph showed a well-defined radiolucency with a corticated border, associated with a horizontally impacted 33, measuring 6 cm × 3 cm [Figure 3]. There was a uniform hydraulic expansion associated with thinning of the buccal cortical plate without discontinuity, extending from edentulous 43 regions to distal aspect of 35. Orthopantomograph revealed a massive unilocular radiolucency in the anterior mandible, crossing the midline extending superiorly from the crest of alveolar ridge inferiorly up to the lower border of the mandible. The lesion caused thinning of the inferior border of the mandible and resorption with a displacement of roots of 34 and 35, respectively [Figure 4]. Radiographic diagnosis of dentigerous cyst was finalized, and radiographic differential diagnosis considered is discussed in [Table 2].
Figure 2: Aspiration with a 24-gauge needle resulted in 0.5 ml of straw-colored, thin, light yellow fluid

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Figure 3: A mandibular cross-sectional occlusal radiograph showed a well-defined radiolucency with a corticated border, associated with a horizontally impacted 33, measuring 6 cm × 3 cm

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Figure 4: Unilocular radiolucent lesion caused thinning of the inferior border of the mandible and resorption with displacement of roots of 34 and 35, respectively

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Table 2: Differential diagnosis based on radiological features

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The complete enucleation of the cyst along with the removal of the impacted tooth was done under local anesthesia [Figure 5]. Intraoperatively, there were many shining cholesterol crystals seen within the lumen. The histopathological examination of the specimen showed cystic wall lined by thin stratified epithelium made up of low cuboidal cells. The epithelium showed transformation into odontogenic epithelium with loosely arranged stellate cells. The underlying connective tissue was densely fibrous [Figure 6]. Based on the histopathology, a final diagnosis of UA was made. The patient was recalled after a week for suture removal. Healing was uneventful, and the patient is currently under follow-up for 1 year, without recurrence.
Figure 5: Surgical enucleation

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Figure 6: Histopathological examination of the specimen (×10) showing epithelial transformation into odontogenic epithelium with loosely arranged stellate cells

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  Discussion Top

UA is an uncommon odontogenic neoplasm, discovered frequently as an incidental finding of a thorough histopathological examination of dentigerous cysts. This lesion has an uncertain pathogenesis, and the causes for cystic degeneration are not clear yet.[3] It is not clear whether they arise from neoplastic transformation of cells from an otherwise nonneoplastic dentigerous epithelium or arise de novo.[7] However, it has been suggested that the reason why some ameloblastomas become completely cystic may be related to epithelial dysadhesion (e.g. defective desmosomes) or, more likely, to the intrinsic production of proteinases (e.g. metalloproteinases and serine proteinases); enzymes that normally degrade the central zone of the enamel organ after tooth development.[3]

Among UA, the “dentigerous” variants associated with a severely displaced third molar in the ramus of the mandible are more common. Premolar region is the next commonly involved site, where it is usually not associated with teeth, the “nondentigerous” type. This pattern is seen more commonly in patients in the fourth or fifth decades.[9] However, our patient presented with a dentigerous variant.

Patients commonly present with swelling or facial asymmetry and infrequently with pain. It is frequently discovered more on routine radiographic screening examinations or as a result of local effects (such as tooth mobility, occlusal alterations, and failure of eruption of teeth) produced by the tumor. Our patient was asymptomatic and unaware of the lesion. This emphasizes the importance of radiographic screening at an early age, especially in the given setting of a missing tooth.

Literature suggests fluids from nonkeratinizing cysts of the jaws, contain the main proteins found in plasma. Our patient showed high-soluble protein content in the aspirate, suggesting a nonkeratinizing cyst.

The most common radiographic presentation is well circumscribed unilocular pericoronal radiolucency around an impacted tooth, mimicking a dentigerous cyst.[1] Characteristic radiographic appearance of this lesion is valuable in arriving at the diagnosis. However, it may present as multilocular lesion also. Eversole et al. reported that the unilocular:multilocular ratio was 13:3 for cases associated with impacted teeth, against an almost equal 8:7 for the nondentigerous types.[10]

Cholesterol crystals are usually associated with odontogenic cysts such as dentigerous cyst, keratocystic odontogenic tumor, and radicular cyst.[11] In the present case, intraoperatively, several cholesterol crystals were found, thus navigating the diagnosis toward noninflammatory odontogenic cyst. Literature search reveals that the origin of cholesterol crystals is not clear, but they are thought to be formed from disintegrating erythrocytes, degenerating epithelial cells, and macrophages.[12] Cholesterol crystals had not been reported with UA, so far.[3]

Histopathologically, UA consists of a dense, uniformly thickened, fibrous connective tissue capsule that consists totally or partially of ameloblastic epithelium, surrounding a solitary large fluid-filled lumen.[13] It is believed that diagnosis of UA may be missed out if careful histopathological examination of the entire specimen of dentigerous cyst is not carried out. The histopathological nature of the lesion dictates the treatment protocol as well as the recurrence rates.[14]

Ackermann classified UA into the following three histologic groups:[15]

  • Group I: Luminal UA: In this variant, the tumor is confined to the luminal surface of the cyst
  • Group II: Intraluminal/plexiform UA: Some lesions contain areas in which the epithelium is thickened with papillary projections extending into the lumen. This histologic pattern is referred to as intraluminal variant
  • Group III: Mural UA: When the thickened lining (either plexiform or follicular) penetrates the adjacent capsular tissue, it is termed a mural variant. Mural variants may be difficult to determine unless multiple sections are examined.

The mural variety is more often associated with the “nondentigerous” type of these lesions while the intraluminal proliferations are more than twice as frequent in “dentigerous” type.

Histologic subgrouping according to Philipsen and Reichart is as follows:[16]

  • Subgroup 1: Luminal UA
  • Subgroup 1.2: Luminal and intraluminal UA
  • Subgroup 1.2.3: Luminal, intraluminal and intramural UA
  • Subgroup 1.3: Luminal and intramural UA.

Although the treatment is largely dictated by the histological pattern, it is difficult to determine the ideal treatment for a particular case preoperatively, which becomes possible only postoperatively after careful histological typing. The treatment guidelines as per histological subtypes are discussed in [Table 3]. Recurrence of the lesion depends both on the histological type (highest 35.7% with mural variant) and type of treatment protocol followed. Late recurrence as long as 7 years has been reported.[17] As reported by Lau and Samman recurrence rates following resection, enucleation, enucleation followed by Carnoy's solution, and marsupialization followed by enucleation were 3.6%, 30.5%, 16%, and 18%, respectively.[18] As suggested by Stoelinga and Bronkhorst in 1988, the use of Carnoy's solution decreases the chances of recurrence after conservative surgical treatment of UAs.[19]
Table 3: Treatment protocols based on histological subtypes

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  Conclusion Top

UA may have many diverse clinical and radiological presentations and may be encountered in any area of the jaw. Thus, it should be considered under differential diagnosis at uncommon sites also, especially when the radiological features are suggestive. This case also highlights the significance of histopathological evaluation of the entire specimen so as to obtain the correct diagnosis, predict biologic behavior, and plan meticulous treatment to prevent recurrences.

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Conflicts of interest

There are no conflicts of interest.

  References Top

Neville BW, Damm DD, Allen CM. Oral and Maxillofacial Pathology. 2nd ed. Philadelphia: Saunders; 2002. p. 589-642.  Back to cited text no. 1
Robinson L, Martinez MG. Unicystic ameloblastoma: A prognostically distinct entity. Cancer 1977;40:2278-85.  Back to cited text no. 2
Rosenstein T, Pogrel MA, Smith RA, Regezi JA. Cystic ameloblastoma – Behavior and treatment of 21 cases. J Oral Maxillofac Surg 2001;59:1311-6.  Back to cited text no. 3
Gold L. Odontogenic tumours: Surgical pathology and management. In: Fonseca RJ, Williams TP, Stewart JC, editors. Oral and Maxillofacial Surgery: Surgical Pathology. Philadelphia: Saunders; 2000. p. 324-97.  Back to cited text no. 4
Philipsen HP, Reichart PA. Unicystic ameloblastoma. Odontogenic Tumors and Allied Lesions. London: Quintessence Publication Company Ltd.; 2004. p. 77-86.  Back to cited text no. 5
Bhalerao S, Chaudhary R, Tamgadge A, Chi A. Unicystic ameloblastoma – A case report. IJCD 2011;2:65-8.  Back to cited text no. 6
Sapp JP, Eversole LR, Wysocki GP. Odontogenic tumors. Contemporary Oral and Maxillofacial Pathology. 2nd ed. St. Louis: Mosby; 2004. p. 134-63.  Back to cited text no. 7
Pizer ME, Page DG, Svirsky JA. Thirteen-year follow-up of large recurrent unicystic ameloblastoma of the mandible in a 15-year-old boy. J Oral Maxillofac Surg 2002;60:211-5.  Back to cited text no. 8
Wood NK, Kuc IM. Pericoronal radiolucencies. In: Wood NK, Goaz PW, editors. Differential Diagnosis of Oral and Maxillofacial Lesions. 5th ed. St. Louis: Mosby; 1997. p. 279-96.  Back to cited text no. 9
Eversole LR, Leider AS, Strub D. Radiographic characteristics of cystogenic ameloblastoma. Oral Surg Oral Med Oral Pathol 1984;57:572-7.  Back to cited text no. 10
Browne RM. The origin of cholesterol in odontogenic cysts in man. Arch Oral Biol 1971;16:107-13.  Back to cited text no. 11
Best CH, Taylor NB, West JB. The red blood cell. In: Physiological Basis of Medical Practice. 11th ed. Baltimore: Williams & Wilkins; 1985. p. 390-7.  Back to cited text no. 12
Philipsen HP, Reichart PA. Unicystic ameloblastoma. A review of 193 cases from the literature. Oral Oncol 1998;34:317-25.s  Back to cited text no. 13
Lee PK, Samman N, Ng IO. Unicystic ameloblastoma – Use of Carnoy's solution after enucleation. Int J Oral Maxillofac Surg 2004;33:263-7.  Back to cited text no. 14
Ackermann GL, Altini M, Shear M. The unicystic ameloblastoma: A clinicopathological study of 57 cases. J Oral Pathol 1988;17:541-6.  Back to cited text no. 15
Philipsen HP, Reichart PA. Classification of odontogenic tumors and allied lesions. Odontogenic Tumors and Allied Lesions. USA: Quintessence Publication Company Ltd.; 2004. p. 21-3.  Back to cited text no. 16
Li T, Wu Y, Yu S, Yu G. Clinicopathological features of unicystic ameloblastoma with special reference to its recurrence. Zhonghua Kou Qiang Yi Xue Za Zhi 2002;37:210-2.  Back to cited text no. 17
Lau SL, Samman N. Recurrence related to treatment modalities of unicystic ameloblastoma: A systematic review. Int J Oral Maxillofac Surg 2006;35:681-90.  Back to cited text no. 18
Stoelinga PJ, Bronkhorst FB. The incidence, multiple presentation and recurrence of aggressive cysts of the jaws. J Craniomaxillofac Surg 1988;16:184-95.  Back to cited text no. 19


  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]

  [Table 1], [Table 2], [Table 3]


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