A case of an intramuscular lipoma in the mental region.

Sir:

Lipoma, a soft-tissue tumor derived from the stroma, is the lesion most frequently encountered by plastic surgeons in clinical practice. In the head and neck region, lipomas commonly develop in the buccal mucosa, tongue, and parotid region,[1,2] but an extremely small number of studies on only 3 cases of lipomas in the mental region, or chin, have been reported. We recently experienced a rare case of an intramuscular lipoma in the mental region. A 35-year-old woman noticed a painless mass in the mental region 3 months before she visited our department for cosmetic improvement, with the concern that the mass may enlarge. Her previous medical history and family history were unremarkable. Macroscopic observation and palpation revealed a poorly movable mass of 10 × 10 mm at the center of the mandible with no abnormalities in the skin immediately above the mass and no sensory abnormalities in the mental nerve territory. The oral mucosa was also normal. Preoperative T1-weighted magnetic resonance imaging (MRI) revealed a hyperintense lesion, whereas fat-suppressed MRI revealed a hypointense lesion, with the mass having absorption values corresponding to lipids. All MRI findings consistently indicated that the lesion was a lipoma.

The tumor was in contact with the mandible with no infiltration. Three months after the initial diagnosis, tumorectomy was performed under general anesthesia by approaching the subcutaneous tumor in the mental region through a midline incision of the lower vestibule of the mouth and detaching the tissues along the mandibular periosteum. A lipoma-like solid tumor of approximately 12 × 6 mm was present in the mentalis muscle in a way that suggested it had infiltrated the muscle (Fig. 1). The inferior part of the tumor adhering tightly to the mandibular periosteum was excised with a wide margin using an electric knife.

Fig. 1.

Intraoperative findings. A lipoma-like solid tumor (approximately 12 × 6 mm) in the mentalis muscle appearing to infiltrate the muscle.

The patient was discharged on postoperative day 2 due to an excellent postoperative course. Histopathological examination revealed that the tumor, located between the striated fibers of the mentalis muscle, consisted of mature adipocytes with no signs of malignancy (Fig. 2). Cosmetic improvement and no local recurrence, sensory abnormalities, or motor dysfunction in the lower lip was observed during a 6-month postoperative observation period.

Fig. 2.

Tissue section stained with hematoxylin and eosin. The tumor consisted of mature adipocytes and was present deep inside the striated fibers of the mentalis muscle, with no signs of malignancy. Scale bar, 200 μm.

Only 3 cases of intramuscular lipomas in the mental region have been reported.[3-5] In these reports, the size of the lipomas was approximately 10–30 mm and the patients were aged 21–77. As in our case, a painless palpable mass was the only subjective symptom in all 3 cases, and lipoma was easily diagnosed based on the preoperative imaging findings in most cases (2 cases). Furthermore, surgical outcomes were satisfactory in all cases due to no recurrence, functional disturbance, or scar deformities. Taken together, surgical removal can be actively indicated for intramuscular lipoma in the mental region.

DISCLOSURE

The authors have no financial interest to declare in relation to the content of this article. The Article Processing Charge was paid for by the authors.