Aggressive nasopalatine duct cyst with complete destruction of palatine bone.

Nasopalatine duct cyst is the nonodontogenic developmental cyst, frequently occurring in the midline of the anterior maxillary region. The clinical presentation of the cyst is often varied and presents a diagnostic difficulty and frequently misdiagnosed as developmental or inflammatory odontogenic cystic lesion. This paper represents a large infected nasopalatine duct cyst presenting with complete destruction of anterior palate and pyriform rim.

Nasopalatine canal develops at the junction of the primary palate and the secondary palate. It communicates the nasal floor with the oral cavity. In general, the epithelial lining in the nasopalatine canal will degenerate; however, in some patients, it persists and proliferates to form a cyst in the anterior midpalatal region which is called as nasopalatine duct cyst or incisive canal cyst. Nasopalatine cyst is often misdiagnosed as inflammatory cyst originating from the incisor teeth due to the proximity of the cyst to the incisors. The cystic lesion in the anterior maxilla is most commonly radicular cyst followed by dentigerous cyst followed by keratocystic odontogenic tumor.[1] It constitutes <1% to 33% (average 12%) of all the cysts of jaw,[1234] but it is one of the most commonly reported nonodontogenic developmental cysts of the jaw. Although nasopalatine duct cyst can occur at any age, the incidence is more common in the late adults between 40 and 60 years age group.[56] However, it can present in young patients[57] also. In this case report, we are presenting the classical features of nasopalatine duct cyst which were found in the clinical, radiographic as well as on histopathological examination.

Case Report

A 40-year-old male patient came with the complaint of pain and swelling in the anterior vestibular region for the past 2 weeks. History revealed recurrent episodes of pain and swelling and spontaneous remission following nasal discharge. On examination, the patient had a well-defined, fluctuant swelling obliterating the labial vestibule from 12 to 22. The swelling also extended in the midpalatal region between two central incisors posteriorly up to the premolar level [Figure 1]. The central incisor exhibited mild Grade 1 mobility buccopalatally without any movement in the corono-apical region. Both central incisors were tender on palpation. On vitality test, the central incisors were found nonvital. Patient had poor oral hygiene and inflamed gingiva with 5 mm of gingival pocket in both central incisors. Patient had generalized bleeding gums. On aspiration, straw-colored fluid with mixture of blood was found [Figure 2]. There was no lymphadenopathy found. The periapical radiograph showed large triangular-shaped radiolucent lesion measuring about 2 cm diameter was present between the two maxillary central incisors [Figure 3]. The lesion had a thin radio-opaque margin with displacement of both the roots in a distal direction [Figure 4]. Mild root resorption was observed in 21 root and the lesions also involved the periapical region of the two lateral incisors. The central incisors had bone only on the cervical region, and the remaining portion was completely in the radiolucent lesion. The nasal septum was found in the middle of the radiolucent lesion. Occlusal view radiograph revealed an oval radiolucent lesion from the central incisor to the 2nd premolar region in the midpalatal region measuring about 3 cm × 2 cm lesion. Due to the proximity of the lesion to the nasal floor, cone-beam computed tomography (CBCT) scan was taken to plan for the surgical procedure which clearly showed the complete breach of both the nasal floor and hard palate with hollowing in the anterior maxillary region [Figure 5]. The patient's medical history was noncontributory. Based on the clinical and radiographic findings, provisional diagnosis of nasopalatine duct cyst was made.

Figure 1

Preoperative intraoral swelling

Figure 2

Aspiration content

Figure 3

Preoperative (a) intraoral periapical radiograph, (b) occlusal radiographs

Figure 4

Orthopantamograph showing distal displacement roots of upper central incisors

Figure 5

(a and b) Cone beam computed tomography images of the lesion showing complete anterior palatine bone loss

The patient was advised about the nature and severity of the lesion, and the complete bone loss of anterior palatine bone was explained. The significance of surgical enucleation of the lesion was explained to the patient and also advised for bone graft placement. The patient gave consent for the cyst enucleation but was not willing for bone grafting procedure. Before the surgery, root canal treatment of the involved teeth was done, and complete scaling was done to improve the oral hygiene.

Before surgery, all preliminary investigations were done, and the results were within normal limit. Due to the mild mobility of the central incisors, splinting of the teeth with arch bar was done before the surgical procedure. The possibility of tooth avulsion or extractions of incisors were explained to the patient, and informed consent was obtained. As the cystic wall was found attached to the nasal mucosa and palatal mucosa, both labial and palatal approach were used [Figure 6]. The cyst was carefully dissected and enucleated, without breaching the nasal mucous membrane or the palatal mucosa. Intraoperatively, the cyst was found to be a capsuled lesion which was adherent in the nasopalatine region of palatal mucosa but was not attached to the root or periodontal ligament. The flap was closed, and palatal acrylic plate was placed to support the palatal mucosa. Postoperative period was uneventful. Histopathologically, it was found to have fibrous capsule with stratified squamous epithelial lining, and final diagnosis of nasopalatine duct cyst was confirmed [Figure 7].

Figure 6

Intraoperative picture showing attachment of the cystic wall with (a) nasal mucosa, (b) palatal mucosa

Figure 7

Histopathological picture showing stratified squamous epithelium (H and E, original magnification, ×10)

Discussion

Nasopalatine duct canal develops as a right and left side canal but generally fuses into single canal. However, three anatomical variations have been reported; wherein, it sometimes appears as two parallel canals or single canal or a Y-shaped canal.[89] Depending on the anatomical structure, the nasopalatine cyst appears as a midline cyst or paramedian cyst when it involves one side of the canal only. However, midline nasopalatine duct cyst is more common than the other types (Stafne 1969).[6]

The etiology of nasopalatine duct cyst is idiopathic or reactive. It has been postulated that localized trauma such as previous endodontic treatment, implant placement or infection or mucous retention may initiate the cellular proliferation and may give rise to nasopalatine duct cyst. It has also been reported to present in association with impacted mesiodens.[510111213] It is not been associated with any habits such as smoking or alcoholism.[4] In our study, it appears to be secondary to chronic periodontitis or nonvital teeth.

The cyst arises from the epithelial lining of nasopalatine duct or from the vomer nasal organ of Jacobson or mucous glands present in the nasal mucosa.[6] Histologically, the nasopalatine duct exhibits different epithelial cells in different region. The epithelium close to the nasal floor has ciliated columnar epithelium, and the one closer to the oral cavity has squamous epithelium and the one in the middle has cuboidal epithelium. It has also been reported containing nerve fibers and melanin or lipofuscin pigments.[41415] Hence, the nasopalatine cyst also exhibits the mixed nature of the epithelial lining. In our case, the cystic lining was of squamous epithelial type.

Nasopalatine duct cyst has been reported to be more prevalent in females.[5] It may appear as extrabony incisive papilla cyst or intrabony lesion. It appears as either asymptomatic which is recognized on routine imaging or may present with pain or swelling or with other symptoms such as burning sensation, tooth displacement, nasal obstruction, or discharge into the nasal cavity or oral cavity.[5] The size of the swelling is variable in size but most often it is <2 cm in diameter. However, occasional cases of large and aggressive lesion up to 52 mm have been reported with complete destruction of labial and palatal bony plates.[51617]

When the nasopalatine duct cyst present at higher level, there is not much effect over the tooth. The nasopalatine duct cyst when it is present at lower level always displaces the tooth and often considered characteristic of the lesion. The tooth vitality associated with the cyst is variable.[1] Most literature reports the presence of lamina dura and maintenance of vitality. However, it has been reported in association with nonvital tooth and periodontally compromised tooth. In our case, both the incisors were nonvital, and the patient had chronic periodontitis with poor oral hygiene. Root resorption is uncommon; however, Shear and Speight have reported cases with root resorption.[613]

Radiographically, it appears as a round, ovoid, pear-shaped, or heart-shaped radiolucent lesion in the middle of the palate. It rarely causes root resorption. Bone expansion is uncommon, and usually, it causes resorption of bone. In our case, the cyst completely eroded the palatal bone and the nasal floor, and the swelling was fluctuant in nature. Nasopalatine duct cyst should be differentiated from the normal nasopalatine fossa. The average size of the normal nasopalatine fossa is 3 mm in anteroposterior, transverse, and in vertical direction. However, Shear and Speight have reported that the mean size of the nasopalatine fossa was as high as 10.19 + 3.24 mm anteroposteriorly and 4.79 + 1.33 mm in width. It is advised that if the radiographic size of nasopalatine fossa was <10 mm without any signs and symptoms, it should be re-radiographed periodically. However, Bodin, Isaacson, and Julin advised for surgical exploration if the size of the radiolucency exceeds 8 mm, or if it shows asymmetric bulging.[6] Aspiration of the radiolucent lesion will help to differentiate a normal nasopalatine fossa from the cyst. CBCT is useful when planning for the surgical enucleation of the lesion as it clearly shows the proximity of the lesion with the nasal floor and the posterior extent in the hard palate. The differential diagnosis of the lesions includes odontogenic cysts and tumors such as dentigerous cyst, lateral periodontal cyst, cystic ameloblastoma, keratocystic odontogenic tumors, and periapical granuloma.[1]

The treatment of nasopalatine duct cyst is enucleation of the lesion. However, marsupialization is considered in large lesions followed by second stage enucleation can be done. Palatal approach has been reported frequently in most of the literature. Autogenous bone grafting can be placed. Recurrence is uncommon following enucleation; however, recurrence rate of 11–30% has been reported in the literature.[14] In our study, we used both palatal and vestibular approach as the cyst was large in size extending from nasal floor to palatal mucosa. Paresthesia of the anterior palatal region has been reported in occasional cases following the surgery.

Conclusion

Apart from odontogenic cysts such as radicular cyst, dentigerous cyst, and odontogenic keratocyst, the nonodontogenic origin of cyst such as nasopalatine duct cyst also should be considered in the differential diagnosis of the radiolucent lesions in the anterior maxillary region. As per the literature review, nasopalatine duct cyst is considered a rare pathology, simple enucleation surgery is often considered curative.

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Conflicts of interest

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