Well-Circumscribed Intramuscular Lipoma of Superior Rectus Muscle

Phantaraporn Tangtammaruk,1 Mongkol Uiprasertkul,2 Mingkwan Lumyongsatien1 1Department of Ophthalmology, Mettapracharak Hospital, Nakhon Pathom, Thailand; 2Department of Pathology, Faculty of Medicine, Siriraj Hospital, Mahidol University, Bangkok, ThailandCorrespondence: Mingkwan Lumyongsatien, Department of Ophthalmology, Mettapracharak Hospital, Nakhon Pathom, Thailand, Tel +66814958985, Fax +6634388744, Email mingkwan@metta.go.thAbstract: Extraocular muscle lipoma is a rare benign mesenchymal tumor of the orbit. We report a case of a 37-year-old woman who presented with chronic progressive proptosis and inferior globe displacement of left eye. External eye examination revealed a yellowish mass at the superior bulbar conjunctiva. Magnetic resonance imaging showed a well-circumscribed mass confined in the superior rectus muscle belly and tendon with a fat signal. Debulking surgery was performed using the transconjunctival and vertical lid split approach. A pathological study demonstrated matured adipose tissue cells encapsulated by a thin layer of fibrous tissue, in addition to the chronic non-specific inflammation of the tenon capsule tissue sample. Histopathological findings of the mass were consistent with a well-circumscribed intramuscular lipoma. The symptoms of the patient were significantly improved 3 months after surgical and short-course systemic steroid treatments. However, long-term surveillance is needed.Keywords: intramuscular lipoma, soft tissue tumor, orbital tumor, extraocular muscle, well-circumscribed lipoma