A 57-year-old male professional pianist player, initially followed for his back pain after traumatic injury requiring L4 to L5 microdiscectomies, presented with acute right forearm pain for 2weeks. The patient reported that the pain began after a mechanical fall, in which he landed on his right wrist with elbow in full extension. The presenting pain was located over the lateral right forearm and was reported as dull and nonradiating. A new visible mobile mass was noted over the lateral forearm on inspection; this was also tender to palpation (Fig. 1). The patient denied neurological symptoms, and he was found to be neurologically intact on examination. The patient was found to have full range of motion at the elbow and wrist, without pain. Localized pain was reproduced with the Cozen test, raising suspicion for tear of the extensor tendons. A noncontrast magnetic resonance imaging of the right upper extremity was performed and revealed a 6 × 4 × 3–cm lipomatous mass located deep between supinator and extensor carpi radialis longus (Fig. 2). The patient was referred to general surgery team for elective lipoma excision. The lipoma was surgically removed, and final pathology report was read as benign intramuscular lipoma (Fig. 3).
Lipomas are the most common type of soft tissue tumors.1 Intramuscular lipomas are a rare subset that originates within the muscle, accounting for less than 1% of all lipomas.2,3 Symptoms depend on location and size of tumor and can present as common musculotendinous pathologies, which may pose a misleading diagnosis. Magnetic resonance imaging is typically the image modality of choice for imaging lipomas, not only to confirm the diagnosis (also strongly suggested by ultrasound and computed tomography) but also to better assess for atypical features suggesting liposarcoma.4
Intramuscular lipomas are rare and may have a misleading musculotendinous presentation, which may lead to a diagnostic dilemma. Advanced imaging may therefore be warranted.
1. Murphey MD, Carroll JF, Flemming DJ, et al: From the archives of the AFIP: benign musculoskeletal lipomatous lesions. Radiographics
2. McTighe S, Chernev I: Intramuscular lipoma: a review of the literature. Orthop Rev (Pavia)
3. Lee JH, Do HD, Lee JC: Well-circumscribed type of intramuscular lipoma in the chest wall. J Cardiothorac Surg
4. Gaskin CM, Helms CA: Lipomas, lipoma variants, and well-differentiated liposarcomas (atypical lipomas): results of MRI evaluations of 126 consecutive fatty masses. AJR Am J Roentgenol