Lipoma involving the masticator space.

The lipoma is a common tumor of mesenchymal origin, usually seen on the trunk and lower limbs. In the head and neck region, it is usually seen in the posterior neck. It is rarely seen in the anterior neck, infratemporal fossa, oral cavity, pharynx, larynx and parotid gland. It may present in a variety of ways. We report a rare case of a lipoma involving the masticator space.

INTRODUCTION

A lipoma is a benign tumor consisting of adipocytes without atypia.[1] It is the most common tumor of mesenchymal origin that may occur in any region of the body where fat is present. It is most commonly seen on the trunk and lower limbs. In the head and neck, lipomas are rare, and account for 1–4.4% of all benign tumors.[2] They are usually seen in the posterior neck region.[3] They are slow growing and nearly always benign.

On clinical examination, lipomas are non-tender, soft, mobile masses. Most subcutaneous lipomas may be suspected with a high degree of accuracy on clinical examination. It is the deep seated or infiltrating lipoma that requires imaging for further assessment.[4]

We report a rare case of a lipoma involving the masticator space. A search of the PUBMED online database yielded only one other case report of a lipoma involving the masticator space.[5]

CASE REPORT

A 40-year-old male patient reported to our unit with a complaint of a swelling on the left side of his face for a duration of 2 years. The swelling had gradually increased in size to reach a size of 5 cm × 5 cm at the time of examination. Local examination revealed an asymptomatic mass present at the left angle region of the mandible that was firm and non-fluctuant. The overlying skin was normal in color and texture. The swelling was more prominent with the teeth clenched and while contracting the masseter, and it extended from the posterior border of ramus toward the anterior border.

There was no intraoral extension of the swelling.

Ultrasonography report was suggestive of a lipoma. Magnetic resonance imaging (MRI) study showed a well-defined, oval-shaped, hyperintense signal in T1- and T2-weighted images involving the masticator space, adjacent to the masseter muscle and the superficial lobe of the parotid gland of the left side [Figure 1].

Figure 1

Magnetic resonance imaging showing the lesion in the left masticator space

The tumor was excised under general anesthesia via an extraoral submandibular incision. Wide excision of the entire lesion was performed. The excised specimen appeared pale yellow in color with a lobulated surface [Figure 2]. Histologic examination showed the mass to consist of mature adipocytes separated by fibrous septae, and a diagnosis of lipoma was made [Figure 3]. There has been no recurrence in 2 years following surgery, and we continue to monitor the patient regularly.

Figure 2

Excised specimen

Figure 3

Histopathology of the excised specimen showing lobules of mature adipocytes

DISCUSSION

Lipomas are common tumors occurring in areas of the body where fat is present The fat in the tumors differs from normal fat in that it is never utilized for metabolic needs of the body.[6] These tumors are usually slow growing and asymptomatic unless they cause mass effect on the adjacent neurovascular structure. Benign lipomas are classified as classic lipoma, angiolipoma, chondroid lipoma, myxolipoma and spindle cell/pleomorphic lipoma.[2] Rarely, a lipoma may infiltrate the adjacent muscle and is called an infiltrating lipoma, which may be of two types; the common intermuscular variety and the rarer intramuscular form. Infiltrating lipomas have a high rate of recurrence. Lipomas are more common in males in the age group of 40–60 years.[7] Rarely, lipomas may be associated with inherited disorders such as Gardner's syndrome, Madelung's disease and hereditary multiple lipomatosis.

The superficial lipomas may be suspected with a high accuracy by clinical examination. The differential diagnosis of superficial lipoma includes Schwannoma, neurofibroma, vascular malformation, sebaceous cyst and lymphangioma. The deeper lipomas need to be assessed by means of imaging modalities such as MRI or computed tomography with appropriate contrast. Surgical excision of the lipoma is curative and recurrence is rare. However, infiltrating lipomas have a high recurrence rate, and the patients must be followed-up at regular intervals. In our case, the lipoma was present in the masticator space and did not involve the masseter muscle or the parotid gland. There have been many case reports of lipomas involving the submandibular and parapharyngeal spaces[89] and only one other reported case of lipoma of the masticatory space.

CONCLUSION

The lipoma is an extremely rare tumor of the head and neck region. We report a rare case of lipoma involving the masticator space. Surgical excision is curative but, depending on the histological subtype of the lipoma, regular follow-up is needed to identify recurrences.