An Atypical Location for an Atypical Lipoma

Saturday, October 25, 2025

12:00 PM - 1:30 PM MT

Location: Kiosk 2

Co-Author(s)

Devon Shannon, MD

Fellow Physician
Emory University Primary Care Sports Medicine Fellowship
Nashville, Tennessee
William M. Jones, MD (he/him/his)

Assistant Professor
Vanderbilt University Medical Center PM&R Program
Nashville, Tennessee

Poster Presenter(s)

Jack E. Kilgore, III, MD

Resident Physician
Vanderbilt University Medical Center
Nashville, Tennessee

Disclosure(s):

Devon Shannon, MD: No financial relationships to disclose

William M. Jones, MD: No financial relationships to disclose

Case Diagnosis: Intramuscular lipoma in the myotendinous junction of the flexor carpi ulnaris muscle

Case Description or Program Description: A 78-year-old right-hand-dominant female was referred for a progressively enlarging mass over 5 years along the volar aspect of the distal ulnar region of the left wrist that appeared without prior injury She had no associated pain, sensory changes, loss of ROM, or weakness in the left upper extremity. The patient denied fevers, chills, night sweats, malaise, or weight loss. The patient previously had a posterior auricular lipoma excised in the distant past. She was initially seen by plastic hand surgery and her symptoms were thought to be due to a lipoma for which she was referred to the PM&R clinic for a diagnostic ultrasound evaluation.

Setting: Outpatient clinic

Assessment/Results: Diagnostic ultrasound of the left volar wrist revealed a large, nontender, non-compressible, well-circumscribed, heterogeneous, intramuscular mass arising from the distal aspect of the flexor carpi ulnaris (FCU) muscle at the myotendinous junction measuring 4 cm x 2.5 cm x 1 cm. There was slight hypervascularity observed around the periphery of the mass, but no evidence of any neurovascular or bony involvement. Left wrist MRI +/- contrast confirmed a well-defined lesion at the myotendinous junction of the FCU consistent with an intramuscular lipoma, or less likely a low-grade liposarcoma.

Discussion (relevance): Although lipoma is the most common soft tissue mass, intramuscular lipoma accounts for less than 1% of these cases. In addition, the most common location for an intramuscular lipoma is in large muscles of the trunk or proximal extremities. This case describes an atypical cause of a soft tissue mass in an atypical location.

Conclusions: An intramuscular lipoma can be an atypical cause for a volar wrist soft tissue mass. Ultrasound can be a noninvasive and effective first-line imaging modality to characterize soft tissue masses of the hand and wrist.