Osseous choristoma of the labial mucosa: A rare case report.

Osseous choristoma is a normal bone tissue in an ectopic position. These are slow growing lesions that are usually completely asymptomatic and only present when there is a disruption in the function of the organ due to its large size as it grows. Definitive diagnosis is obtained only after the histopathological examination. The etiology remains still questionable. The treatment of choice is surgical excision. Here we report a case of choristoma in the lower labial mucosa in a 47-year-old female.

Choristoma is defined as a tumor-like mass of normal cells or tissue that develops in an ectopic location.[1] Choristoma may be consists of several different tissue types. These include bone, cartilage, glial tissue, gastric mucosa, and tumor-like masses of sebaceous glands. Monserrat was the first to report an osseous lesion in the tongue in 1913 and labeled it as “lingual choristoma”, the term that usually describes neoplastic pathology.[2] Krolls et al. changed this term later to “osseous choristoma” in 1971, which means a mass consisting of normal cells in an abnormal location.[3] He used this term as he noticed that these lesions were not osteogenic in origin and not progressively enlarging like benign lesions. Osseous choristoma is an uncommon alteration of the soft tissues in the oral cavity and has a tumoral composition arising from primordial cells in an abnormal location,[345] as well as having a predilection for the soft tissues of the head and neck.[6]

Osseous choristoma is a well circumscribed benign growth of normal, mature osseous tissue in ectopic sites. Osseous choristoma of the tongue is an extremely rare condition, of which only 66 cases have been reported in the literature till now. However, osseous choristoma occurring in the lip is rarest. This is first case report describing regarding osseous choristoma occurring in the labial mucosa. The etiology remains already questionable. The treatment of choice is surgical excision.

Case Report

A 47-year-old female was referred to Department of Oral and Maxillofacial Surgery with a chief complaint of pain and swelling of the lower lip. History of present illness revealed that swelling was since 1-year. Initially, it was peanut size, later increased to present size. Intra-oral clinical examination revealed a well circumscribed swelling measuring 6 cm × 6 cm in dimension i.r.t 41, 42, 43. It was covered with a thin normal looking mucosa, no inflammatory or erythematous areas seen around the swelling. Palpation showed a firm mass, bony hard in consistency, not fixed to the underlying tissue. After taking consent from the patient, surgical excision was planned. The patient underwent an uneventful excision under local anesthesia and the excised specimen was sent for a histopathological examination.

Grossly, the specimen consisted of a gray-white mass measuring 1 cm × 1 cm in dimension. The mass was hard in consistency and had a smooth surface. The specimen was immediately fixed in 10% formaldehyde and later subjected for decalcification. The tissue sample was decalcified and embedded in paraffin. Serial histological section at 6 μ each were made, and then, stained with Hematoxylin and Eosin technique. Microscopic observation revealed parakeratinized stratified squamous epithelium cells with an underlying stroma is composed of dense connective tissue with few blood capillaries [Figures 1 and 2].

Figure 1

H and E, stained section shows mature lamella lined by stratified squamous epithelium

Figure 2

H and E, stained section shows hematopoietic areas

The lesion is composed of mature lamellar bone, osteocytes, and adipocytes. The specimen is also showing hematopoietic areas. With these histological findings along with clinical findings suggestive of the Osseous Choristoma of the labial mucosa was made.

Discussion

The term osseous choristoma was introduced by Krolls et al. in 1971.[3] A choristoma is defined as a histologically normal tissue proliferation or nodule of a soft tissue type not normally found in the anatomic site of proliferation. Choristoma of the mouth may be composed of several different tissue types. These include cartilage, bone, glial tissue, gastric mucosa, and tumor-like masses of sebaceous glands.[78]

Most frequently observed choristomas’ of the oral cavity are those that consist of bone.[910] The age range for reported cases of intraoral choristomas’ is between 8 and 73 years. Most intraoral choristomas’ develop in dorsal surface of the tongue around the foramen caecum, but lesions have also been reported in the tongue, buccal mucosa, and the lingual alveolus of the mandible. Clinically, it grows as a pedunculated lesion or firm nodular with size of mass may range between 0.5 and 2.0 cm in size. Most patients are unaware of the lesion, but may feel the symptoms of pain, dysphagia, or sometimes may have choking sensation, and nausea also have been reported in some cases.[911] In the literature (PubMed search revealed), 88 cases have been described regarding the osseous choristoma in regard to tongue and buccal mucosa in common, but not in relation to the labial mucosa. The osseous choristoma to arise in the age group of 12–62 years of age with the lesion occurring more frequently in the fifth decade of life. It has a slightly predisposition to occur more commonly in females than males with a ratio of 1.5:1.[12]

Although there are various theories regarding the etiology of OCs, their exact origins remain mysterious and both developmental and trauma origins have been reported. Histologically, these are choristoma consists of a well-circumscribed mass of viable lamellar bone with a well-developed haversian canal system, surrounded by dense, fibrous connective tissue, and covered with stratified squamous epithelium.[713141516] Occasionally, hematopoietic or fatty marrow has been reported in the osseous lesions.[7171819]

The lesion reported here is a rarest type of osseous choristoma seen in the labial mucosa and is the first ever reported a case of osseous choristoma originating in the labial mucosa. The number of reported cases or literatures is insufficient, to review this particular type of osseous choristoma. Awareness of this entity is required so that an early and accurate diagnosis can be made.

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Conflicts of interest

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