Osseous choristoma of the periodontium.

Osseous choristoma is a rare, benign lesion of the oral cavity occurring usually on the tongue. It appears as a tumorous mass of normal bony structure with mature cells in an ectopic position. Some lesions represent developmental malformations, whereas others may be reactive lesions, after trauma or chronic irritation. This is the first ever reported case of an osseous choristoma of the periodontium in the lingual aspect of posterior mandible.

INTRODUCTION

Osseous and cartilaginous lesions of the intraoral soft tissues are uncommon. Kroll and co-workers reported 24 cases of intraoral soft tissue osseous lesions. They favored the term, choristoma, for these lesions, since they represented tumor like growths of histologically normal tissue in an abnormal location.[1] According to some investigators, choristoma refers to a tumor like growth that has developed from groups of primordial cells located at a site remote from the original tissue or organ.[2] The term osteoma is defined as a benign, progressively enlarging, neoplasm of bone originating from osteogenic tissue, and closely associated with a part of the skeletal structure. However, most investigators claim that the biologic behavior of the lesion does not fulfill the criteria of a true neoplasm, and there isn′t a close relation to the skeleton.[3] Osseous choristoma (OC) is a rare tumor composed of normal lamellar bone occurring at a site where bone is not normally found.[1] Choristomas’ occur most frequently in the tongue[4] and less commonly on other sites such as buccal mucosa[56] and alveolar mucosa.[78] The occurrence of such lesions in the periodontium is very rare. We report a case of an osseous choristoma which was present on the lingual aspect of the left second premolar and first molar region.

CASE REPORT

A 46-year-old male reported to Postgraduate Clinic, Department of Periodontics, Jaipur Dental College and Hospital, Rajasthan, India, for the evaluation of an abnormal growth on the lower jaw [Figure 1]. He was otherwise in good health, and his medical history and family history were noncontributory. The patient reported that the growth present lingually in relation to the left second premolar and first molar had been there for four years. It started as a small growth, but increased in size in the last four months. The lesion was asymptomatic, however, the lesion started to interfere with mastication.

Figure 1

Tumor mass irt mandibular left second premolar and first Molar

Visual examination revealed a slightly elevated mass on the lingual aspect of lower left second premolar and first molar. Also, the patient had bilateral mandibular tori in relation to the mandibular second premolars. The overlying mucosa appeared normal and the margins were well defined. Palpation revealed a firm, non-tender, well-circumscribed, non-motile, and sessile mass, approximately 10 mm in diameter. A clinical attachment loss of 12 mm was recorded between the mandibular left second premolar and first molar. A mandibular occlusal and panoramic radiograph revealed a well circumscribed, radiopaque spherical mass on the lingual aspect of the left side of the lower jaw.

The differential diagnosis included a peripheral ossifying fibroma and fibrous hyperplasia. Removal of the mass was accomplished by both sharp and blunt dissection under local anesthesia. The excised mass was approximately 10 mm in diameter. The specimen was fixed in 10% formalin and submitted for histopathologic examination. The patient was prescribed oral amoxicillin 500 mg t.i.d (thrice daily) for seven days. There were no postoperative complications, and clinical and radiographic examinations, three months postoperatively, revealed normal healed area and no recurrence of the mass.

The pathologic specimen consisted of 1×0.8×0.8 cm, smooth-surfaced white tan mass [Figure 2]. Microscopic examination showed a well circumscribed mass composed of well formed lamellar bone with Haversian canals surrounded by dense fibrous connective tissue. Overlying epithelium was ortho-keratinized stratified squamous epithelium [Figures 3 and 4]. One year follow-up showed no recurrence [Figure 5].

Figure 2

The excised specimen

Figure 3

Microphotograph of the histological slide from the excisonal biopsy

Figure 4

Microphotograph of the histological slide from the excisonal biopsy

Figure 5

Post operative at 1-year

DISCUSSION

A choristoma (heterotopic tissue) is defined as a histologically normal tissue proliferation or nodule of a soft tissue type not normally found in the anatomic site of proliferation. Several different tissue types may occur in the mouth as choristomas′. These include bone, cartilage, gastric mucosa, glial tissue, and tumor-like masses of sebaceous glands.[2] However, the most frequently observed choristomas’ of the oral cavity are those that consist of bone.[79] These lesions have also been called soft tissue osteomas, but osseous choristoma is a more accurate term, as the lesions are not true neoplasms.[1]

The age range for reported cases of intraoral choristomas’ is between 8 and 73 years; however, the majority have been diagnosed in women between the age of 20 and 40 years. Most intraoral choristomas’ develop in the area of the foramen caecum, but lesions have been reported in the anterior and ventrolateral surface of the tongue; in the buccal mucosa and the lingual alveolus of the mandible. Clinically, it develops as a firm nodular or pedunculated lesion between 0.5 and 2.0 cm in size. Most patients are unaware of the lesion, but symptoms of pain, dysphagia, gagging, choking, and nausea have been reported.[7]

Since the intraoral choristoma is rare, most such lesions are misdiagnosed as other soft tissue tumors. The differential diagnosis for intraoral choristoma depends on the location of the lesion. When lesion is located near the foramen caecum, lingual thyroid nodule must be considered. Hyperplastic lingual tonsil and salivary gland neoplasm should also be included in the differential diagnosis. When the lesion is located in the anterior and lateral aspect of the tongue, fibroma, granular cell tumor, and neural tumor should be considered. Lesions on the ventral surface of the tongue may resemble salivary gland neoplasms, mucous retention phenomena, lipomas, neural tumors. OCs of the tongue are mostly asymptomatic, although some patients may present symptoms of pain, dysphagia, foreign body sensation, throat irritation, snoring, nausea, and compromised tongue mobility.[12]

When the lesion is located on the alveolar ridge, peripheral giant cell granuloma or fibrous hyperplasia should be included. In the differential diagnosis, when the lesion is pedunculated and has a verrucal surface, it may clinically resemble a papilloma.[7]

Although there are various theories regarding the etiology of OCs, their exact origins remain unknown and both developmental and trauma origins have been reported. Ossification of branchial arch remnants, ossified calcified lymphatic tissue, and remnants of the thyroid gland have all been suggested as possible etiologies.[1257] In the case reported here, trauma is considered a possible etiological factor.

Histologically, the intraoral choristoma consists of a well- circumscribed mass of viable lamellar bone with a well-developed Haversian canal system, a well-developed mass of viable cartilage, or a mixture of bone and cartilage surrounded by dense fibrous connective tissue. Occasionally, hematopoietic or fatty marrow has been reported in the osseous lesions. Osteoblastic or osteoclastic activity is rarely present.[7]

Unilateral intraoral masses may be attributed to a number of pathological conditions of various origins. In the differential diagnosis of the present case, peripheral ossifying fibroma, heterotopic ossification, and torus were considered.

Peripheral ossifying fibroma (POF) can arise from mesenchymal cells of periodontal ligament which are capable of producing hyperplasia. Pluripotent cells of periodontal ligament transform or metaplastically change in osteoblasts, cementoblasts, and fibroblasts. POF must be associated with gingival tissue and diagnosis cannot be used for lesion at other oral sites. Shepherd reported this entity as alveolar exostosis in 1844. It is a painless, hemorrhagic, lobulated mass of gingiva, or alveolar mucosa with large layers of ulceration. Early lesions are irregular and red, but older lesions have smooth salmon pink surface and are indistinguishable from irritation fibroma. POF are 1-2 cm in size and can enlarge up to 4 cm. Early growth is rapid, and occasionally, multiple lesions can occur. Microscopically, submucosal proliferation of primitive, oval mesencymal cells in the hall mark of POF. Islands and trabaculae of woven or lamellar bone with osteoblastic rimming surrounded by chronic inflammatory cells can be seen. POF is exclusively found on alveolar bone surface. No cartilage or marrow is produced by POF. Whereas OC shows submucosal proliferation of normal mature bone or cartilage embedded in fibrovascular stroma with psuedoencapsulation. Lamellar bone with fatty marrow can be present.[10]

Heterotopic ossification shows plump fibroblasts and reactive bone with osteoblastic rimming and is usually present in the muscle.[11] A possibility of multiple tori was thought. But a torus arises from the bone which was not seen in our case.

The intraoral choristoma is treated by means of surgical excision. In most cases with follow-up, recurrence has not been reported. Similarly, in the presented case, there was no recurrence after one year of follow-up [Figure 5].

The lesion reported here is a rare type of Osseous choristoma and is the first ever reported case of OC originating from the periodontium. The number of reported cases is insufficient, to completely describe OC. In order to increase awareness and knowledge regarding OC, new case reports should include clinical, radiographic, and histological findings and follow-up reports.