Intramuscular Lipoma of the Sternocleidomastoid Muscle: A Rare Entity Revisited

Abstract

Intramuscular lipomas, typically found in subcutaneous tissue, rarely affect deeper muscular planes, especially those of the head and neck region. The following are 3 cases of intramuscular lipomas involving the sternocleidomastoid muscle. The first 2 patients presented with painless, palpable masses confirmed by diagnostic imaging as well-circumscribed intramuscular lipomas. One was treated surgically, while the other was managed conservatively with monitoring and close follow-up. The third patient reported dysphagia associated with occasional dyspnea and mild pain. The mass was identified as infiltrative lipoma and was resected surgically. Complete tumor removal with no recurrence at 6 months was observed for the first and last cases. The second case was serially followed at 3 and 6 months with no interval changes. We report the largest case series on intramuscular lipomas of the sternocleidomastoid muscle to enhance our understanding of this rare entity.

Keywords: Intramuscular; benign pathology; lipoma; lipomatous tumor; sternocleidomastoid muscle.

Figure 1.

(a) Preoperative axial CT scan showing a well-circumscribed well-defined non-enhancing fat-attenuating mass in the left side of the neck; (b) Intraoperative image of the lipoma invading the SCM muscle and adhering to the muscle fascia.

Figure 2.

(a) Histologic appearance of an overall well circumscribed intramuscular lipoma with mature univacuolated adipocytes of fairly uniform size (H&E, X20); (b) Focal area of infiltration within the surrounding skeletal muscle (H&E, X40); (c) Desmin immunostaining to highlight the skeletal muscle.

Figure 3.

(a) T1-weighted MRI revealing an intramuscular lipoma extending between neck level VB and the supraclavicular region, anteriorly limited by the sternocleidomastoid muscle; (b) Intraoperative image of the lipoma invading the SCM muscle and adhering to the muscle fascia.