Oral Leiomyoma – A Rare Presentation in a Child

Introduction

Leiomyoma is a benign tumour originating from the smooth muscle. It is uncommon in children and if it occurs in the oral cavity, it is considered rare. World Health Organization (WHO) has histologically classified leiyomyoma under three subtypes: solid leiomyoma, angiomyoma (vascular leiomyoma), and the rare form i.e., epithelioid leiomyoma (bizarre leiomyoma/ leiomyoblastoma).^1-6

The tumour could occur at any location. However, it frequently occurs in the uterine myometrium (95%), followed by skin (3%), gastrointestinal tract (1.5%) and the rest < 1% are seen in the head and neck region. The low incidence is attributed to the relative paucity of smooth muscle; the reported incidence in the oral cavity is only 0.065%.^1-3

Usual clinical presentation is described as small (<2 cm), solitary nodular mass, having slow growth, presenting in the tongue, lips, palate and buccal mucosa. Generally, it is asymptomatic but may be accompanied with symptoms such as pain or difficulty in chewing during mobility and pain from the dentition.^4,5

Sometimes there may be difficulty in differentiating a leiomyoma from other mesenchymal tumours. The diagnosis is confirmed by a histological study. Excision of the mass with safety is the main treatment for leiomyoma and reported recurrence is extremely rare. We present a case of leiomyoma of oral cavity in a child and its management.

Case Report

A nine-year old girl presented with a complaint of a proliferative growth/mass in the oral cavity on the right lower jaw for past three months. Difficulty in speech and chewing were reported since last two months due to the growth. The girl was apparently normal till three months back after which she noticed a small swelling over the right lower jaw in the mouth which gradually increased to a size of 5 × 4 × 3 cm. No history of pain in the growth, bleeding on mastication or difficulty in closing the mouth was given. There was no history of any previous dental procedures and the patient had permanent dentition in all quadrants.

On local clinical examination, the patient was able to close the mouth fully and the growth was seen in the right posterior dento-alveolar region of the lower jaw (Figure 1 & 2). The growth was measuring about 5×4×3 cm, was non-tender, firm in consistency, with irregular surface extending from 44 to 47. Clinically, a provisional diagnosis of ossifying fibroma was made.

X-ray of the mandible (Figure 3 & 4) showed exophytic bony projection arising from the right mandible into the oral cavity, suggesting osteochondroma. Excisional biopsy was planned for the growth and the child underwent complete excision of growth along with 5 mm normal margin (Figure 5 & 6). The teeth adjacent to the growth, i.e 45, 46, 47 were extracted. Suturing was done with vicryl 4-0 on round body (Figure 7). Post-operative recovery was without any complications. Using H and E staining (Figure 8) and Immunohistochemistry (IHC) (Figure 9), a rare diagnosis of oral leiomyoma was confirmed. Postoperative recovery was uneventful and there was no evidence of recurrence during one year follow up following excision.

Histopathology

On Immunohistochemistry (IHC), the cells tested positive for SMA and negative for S100. Ki67 was focally around 5%, supporting a diagnosis of leiomyoma (Figure 8 and 9). 

Discussion

Leiomyoma is defined by the World Health Organization as a “circumscribed, benign, often cutaneous tumour composed of intersecting bundles of mature smooth muscle cells”.⁶

Oral leiomyoma has a low incidence and can appear at any age, but the greatest prevalence is in the 4^th and 5^th decades of life with a slight predilection for female gender.1,2,7 Frequent locations in the oral cavity are lips, tongue, buccal mucosa, hard and soft palates, and less commonly found on gingiva, dento-alveolar region of jaw.⁷ Our case was of a 9-year girl child with lesion in dento-alveolar region of right lower jaw, which was a rare occurrence.

Usually it presents as a slow-growing mass that may or may not exhibit ulceration in the oral cavity.⁵ Symptoms also may vary. Patients often seek dental consultation for teeth mobility or even for difficulty in chewing due to tender teeth.⁸ In the present case, the patient presented with a slow growing mass in the mouth with difficulty in chewing. The patient consulted a private dental clinic for tooth mobility.

Clinically it is maybe difficult to differentiate a leiomyoma from other mesenchymal tumours such as fibroma, myofibroma, neurofibroma, lipoma, or leiomyosarcoma. The differential diagnosis can also include salivary gland neoplasms such as deep seated mucocele and pleomorphic adenoma, vascular tumours (lymphangioma, haemangioma, pyogenic granuloma, etc.), and soft tissue cysts, such as dermoid cysts. When it is located in the dento-alveolar region adjacent to teeth, the tumour can be confused with a periodontal lesion.^1,5,7,9 In the present case, clinically it was assumed to be an ossifying fibroma as the growth was firm with absence of pain and the final confirmed diagnosis of oral leiomyoma was determined by histological analysis.

In the present case, X-ray of the mandible showed an exophytic bony projection arising from the right mandible into the oral cavity, suggesting an osteochondroma and the possibility of intraosseous leiomyomas was not considered as it is a very rare finding. Some of the possibilities with respect to the origin are smooth muscles of vascular walls and heterotopic embryonal tissues. Owing to its rarity, it is generally not considered in the radiographic differential diagnosis. Other possible diagnostic considerations include central giant cell lesion, ameloblastoma, myxoma, traumatic bone cyst, haemangioma, neurofibroma and sarcoma. Radiographic presentation of angioleiomyoma can be a unilocular or multilocular radiolucent lesion with either an ill-defined or a well-defined sclerotic border. Cortical expansion of the alveolar plates and root resorption may be evident.¹⁰

In the present case, the histopathology and immuno-histochemistry findings showed that the lesion cells were positive for SMA and negative for S100. Ki67 was focally around 5%, and it supported the diagnosis of leiomyoma.

The treatment of choice is surgical excision including an adequate safety margin of the adjacent normal tissue. Surgery has been used as the only option for the treatment in all leiomyomas described in literature.^1,2,5,7,9 There are no reports of recurrence after total excision, and this confirms the need for careful total excision of the lesion. In our case, we conducted a complete excision of the mass with 5 mm normal margin and postoperative recovery was uneventful. There was no evidence of recurrence during one year follow up following excision.

Oral cavity leiomyoma in children is a rare entity with a good prognosis. It is characterized by a small, solitary, asymptomatic, nodular mass and confirmatory diagnosis is made based on histological study. The treatment of choice is complete surgical excision.

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