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After months of right shoulder pain, a 70-year-old man undergoes work up of a right arm mass with a MRI and also has a CT of his chest/abdomen/pelvis. A representative MRI image is shown in Figure A. He has difficulty using his arm because of the increasing size of the mass. The CT scans shows no evidence of metastatic disease. What is the next step in management?
Chemotherapy followed by surgery
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The T1-weighted MRI shows a soft tissue homogeneous mass that has the same signal intensity as fat, and is intramuscular. Based on the history in the stem, and the imaging provided, the patient has an intramuscular lipoma. These are slow growing and painless. Biopsy of these lesions is not necessary because the diagnosis can usually be made on MRI. Dalal et al. provide a review of lipomatous masses, commenting that lipomas are very common and comprise 50% of soft tissue neoplasms, and that marginal surgical excision is the treatment and recurrence rates range from 15-60%.
Dalal KM, Antonescu CR, Singer S.
J Surg Oncol. 2008 Mar 15;97(4):298-313. PMID: 18286473 (Link to Abstract)
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A 55-year-old man complains of chronic pain and fullness in his proximal posterior thigh that is worse with sitting. Radiograph, MRI, and biopsy are shown in Figures A, B, C, and D, respectively. What is the most likely diagnosis?
The clinical presentation is consistent with a intramuscular lipoma. The radiograph shows a soft tissue density on the left side. The axial MRI images reveals a mass within the gluteus maximus that is bright on T1 and dark on the STIR image. The pathology shows lipoblasts and muscle infiltration which is characteristic of these tumors. The cited reference by Damron et al reviews common soft tissue masses seen by orthopaedic surgeons. They outline an algorithm for evaluation and management of both benign and malignant tumors. Treatment for intramuscular lipomas involves surgical resection only if symptomatic, as these tumors are benign. Matsumoto et al reviewed MRI findings of intramuscular lipomas and found that imaging characteristics varied from a homogeneous mass as commonly seen in an ordinary (superficial) lipoma, to a large, inhomogeneous lesion with an infiltrative margins. Infiltrative margins did not indicate malignancy.
Damron TA, Beauchamp CP, Rougraff BT, Ward WG Sr.
Instr Course Lect. 2004;53:625-37. PMID: 15116652 (Link to Abstract)
Matsumoto K, Hukuda S, Ishizawa M, Chano T, Okabe H.
Skeletal Radiol. 1999 Mar;28(3):145-52. PMID: 10231912 (Link to Abstract)
Matsumoto, SRAD 1999
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This lecture describes the clinical, radiographical, and pathological features o...