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Oral Pathology

Author: Dr Minhaj Anwer, Dr Kausar J Khwaja, Dr. Nasir A Salati.


Abstract:
Lateral periodontal cysts are rare, asymptomatic odontogenic cysts which are difficult to diagnose clinically. Although radiographic findings reveal unilocular, radiolucent regions between mandibular lateral incisors and canines, definitive diagnosis is made only by histopathological findings. Microscopic findings reveal clusters of cells, also called as plaques or theques, which are largely glycogen rich, and are positive for per-iodic stains. The purpose of this paper is to report case of lateral periodontal cyst located in the anterior region of mandible and to discuss the clinical, radiological and histopathological features of lateral periodontal cysts.

Introduction:
The lateral periodontal cyst is a relatively uncommon odontogenic cyst of developmental origin1, 2, and 3. They are generally asymptomatic and are generally revealed as accidental radiographic finding. Lateral periodontal cyst is located mainly between the roots of vital mandibular canines and premolars4,5. These cysts are now considered to be an independent entity since the World Health Organization (WHO) classified them as such in the 1992 monograph on “The Histological Typing of Odontogenic Tumors.” The first well-documented case of a lateral periodontal cyst was reported by Standish and Shafer in 1958.. The diagnosis of lateral periodontal cyst is primarily based on some characteristic histopathologic features.Some authors have postulated that the lateral periodontal cyst is the intra-bony counterpart of the gingival cyst in the adult.

Case report:

A 30 year old, married female patient reported to the Oral diagnosis unit of Dr Z.A. Ziauddin College, Aligarh with chief complaint of painless swelling in right mandibular premolar region. The patient reported that small painless asymptomatic swelling was seen approximately 14 months before, and for past several weeks, mild dull pain elicited during mastication.Clinical examination revealed Grade 1 mobility of lower right first premolar. The palpation of vestibular surface of the alveolar process in the region of lower right premolars was asymptomatic. Both teeth were found to be vital. No gross deformity was observed on extra-oral inspection (Fig: 1). Radiograph of the area shows a well circumscribed, unilocular, pear shaped radiolucency between the roots of first and second premolar region (Fig: 2). On the basis of these findings, a clinical diagnosis of lateral periodontal cyst was made. Local anaesthesia was used and cyst capsule was detached from the adjacent bone. A total enucleation of the lesion was done.

image006 image008 image010

Fig:1

Fig: 2 Fig:3

After enucleation, the cyst was histologically examined. Histological sections showed a single cavity lesion lined by epithelium of variable thickness, sometimes displaying one or two layers of cuboid cells. Some areas formed thick clusters of cells more voluminous than rest of cells. The capsule consisted of fibrous tissue with adequate collagen. There was no evidence of any inflammation (Fig: 3)). The histological findings supported the diagnosis of lateral periodontal cyst of developmental origin.

Discussion:
LPC is considered as developmental odontogenic cyst with unusual occurrence usually associated with vital teeth16,17. LPC represents approximately 0.8% to 2% of all odontogenic cysts18,19. LPC is more prevalent in adults in the 5th - 7th decades, with equal sex predilection20. The most frequently reported location is mandibular premolar area, followed by the anterior region of maxilla6,8. Most of the studies have found LPCs to be less than 1 cm in diameter7,8 and 21.

LPC may arise from reduced enamel epithelium, remnants of dental lamina and cellular remnants of Malassez1,9,11. The first hypothesis is that the cyst is lined by non-keratinized epithelium, which resembles reduced enamel epithelium and may be the source of origin. One more hypothesis believes dental lamina remnants important for its origin, based on the fact that LPC histo-pathologically presents glycogen-rich clear cells, which are also seen in the dental lamina.

Some believe that epithelial remnants of Malassez are important in its etio-pathogenis. LPCs are differentiated from inflammatory cysts and keratocystic odontogenic tumours on basis of clinical, radiographic and microscopic findings 21. This type of cyst should not be confused with a radicular cyst in a lateral position developing as a consequence of inflammation from an infected or necrotic branch of the pulp canal. Clinically, there must not be a communication between the cyst's cavity and the oral environment19,20,21. In order to establish the proper diagnosis, an inflammatory origin as well as exclusion of a possible odontogenic keratocyst must be ruled out clinically and histologically.Occasionally, LPC may be multicystic, and called as odontogenic botryoid cyst , because macroscopic features resemble “bunch of grapes” (from the Greek word “botrios”)11,21. It is believed to have high recurrence rate22.

Radiographically, the cyst presents as a well circumscribed round or teardrop-shaped radiolucent area with a radiopaque rim, located laterally to the root of a vital tooth. The periodontal ligament space doesn’t show any abnormality. X-ray findings resemble anatomic radiolucencies, such as the mental foramen, maxillary sinus and the nutrient canals, radicular cysts or other cysts of the jaws. It may resemble a cyst that develops laterally through a side channel accessory in a non vital tooth12.

Histopathologically, LPC is a developmental cyst characterized by a thin layer of nonkeratinized epithelium with a thickness of 1 - 5 mm, which resemble the reduced enamel epithelium14,21. Nonkeratinized squamous epithelium is composed of 1 - 5 layers of cells displaying a palisade distribution. The epithelium lining can be rich in epithelial plaques composed of the clear fusiform cells rich in glycogen. Some areas of the epithelial thickening, referred to as plaques or theques, are commonly found, and the connective tissue subjacent to the epithelium exhibits a zone of hyalinization. The walls of the cyst consist of mature collagen fibrous tissue12,21. A rare variant of LPC, Odontogenic botryoid cyst has higher rate of recurrence 23,24 and unusual presentation25,26.

Histopathological findings reveal multiple cystic spaces lined by nonkeratinized stratified squamous epithelium14, 25. LPC is believed to cause isolated bone defects according to some studies10,27. The gingival cyst of the adult is believed to be soft tissue variant of LPC28. It rarely reveals any radiographic findings15. Some authors state that both lesions have the same histogenesis and clinical features28. New studies indicate LPCs distinct from gingival cysts.

The treatment of the lateral periodontal cyst is surgical ablation and if at all possible the affected tooth should be preserved, which sometimes is difficult13,17. The recurrence is uncommon with good prognosis.

Conclusion:
Here we have discussed a rare odontogenic cyst which has characteristic radiographic and histopathological findings. Special stains like PAS are of importance in its diagnosis. Sometimes this presents as botryoid odontogenic cyst which due to high recurrence rate can be challenging to treat. Proper microscopic and immune-histochemical studies are helpful to arrive at definitive diagnosis.

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