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A large intermuscular shoulder lipoma causing pain and weakness in an 87-year-old patient: a case report

https://doi.org/10.1016/j.jseint.2020.10.006 2666-6383/© 2020 The Author(s). Publishe license (http://creativecommons.org/license Rotator cuff dysfunction is more common with advancing age; the prevalence of full-thickness rotator cuff tears has been estimated at 22% in patients older than 65 years3 and 51% in patients older than 80 years,19 although many of these arise insidiously and remain asymptomatic. Chronic rotator cuff insufficiency may progress to cuff tear arthropathy,12 often characterized by declining active shoulder motion and dysfunction. However, not all older patients presenting with insidious shoulder pain, weakness, and limited mobility have a large chronic rotator cuff tear or cuff tear arthropathy. We report on an older patient with these symptoms resulting from a large intermuscular lipoma displacing the supraspinatus and infraspinatus muscles and compressing the suprascapular and axillary nerves.

The patient is an active 87-year-old woman, living independently without chronic medical problems, with chief complaint of greater than one-year history of insidious onset and progressive dominant right shoulder pain. She had received initial conservative treatment for rotator cuff disease elsewhere comprising nonsteroidal medications and a subacromial space corticosteroid injection but neither of these provided any relief. Her right shoulder pain had become severe and persistent, and interfered with sleep and activities of daily living.

Physical examination
The patient appeared healthy and spry and could get on and off the examination table independently and with ease. Palpation of the right shoulder revealed a soft mass overlying the supraspinatus fossa and tenderness over the suprascapular notch region but no subacromial or glenohumeral crepitance. Active right shoulder range of motion was limited: forward elevation to 90 , abduction to 70 , external rotation to neutral, and internal rotation to L5. Strength testing revealed an external rotation lag compared with 4þ/5 external rotation strength on the left. Deltoid and internal rotation strength testing revealed 4þ/5 strength and belly press test was normal. The patient rated her pain as 9/10 and reported an American Shoulder and Elbow Surgeons (ASES) score of 17/100 and 0 "yes" responses on the Simple Shoulder Test.

Imaging
Plain radiographs comprising true anteroposterior radiographs in internal and external rotation and axillary lateral views revealed no signs of chronic rotator cuff insufficiency or glenohumeral arthrosis. Noncontrast magnetic resonance imaging (MRI) revealed a large irregular posterior shoulder mass, with a thin capsule and without any obvious septations or Institutional Review Board approval was not required for this case report. The patient was informed that details of her case would be collected and submitted for publication. The patient consented to the use of this information. Statement of Informed Consent: The patient was informed that details of her case would be collected and submitted for publication and she consented to this. heterogeneity, extending between the supraspinatus and infraspinatus muscles and along the scapula, consistent with an intermuscular lipoma ( Fig. 1, a-c). The mass measured 7.3 x 9.0 x 5.2 cm in craniocaudal, transverse, and anteroposterior dimensions. The MRI demonstrated teres minor muscle atrophy but no rotator cuff tear or tendinosis; the supraspinatus and infraspinatus muscle bellies were displaced medially owing to a mass effect.

Diagnosis
The patient was diagnosed with a large intermuscular lipoma vs. low-grade liposarcoma with pain and weakness attributed to compression of the axillary nerve branch to the teres minor and the suprascapular nerve distal to the spinoglenoid notch. An oral prednisone taper was prescribed but this provided only transient pain relief. The patient lacked any chronic medical problems and desired definitive treatment to eliminate the intensifying right shoulder pain that had failed multimodal conservative treatment and to resume her independent active lifestyle. Consequently, we elected to proceed with surgical excision of the right shoulder mass.

Operative details
After the induction of general anesthesia, the patient was positioned in a modified lateral decubitus position (Fig. 2a). A 12-cm incision was made over the posterior shoulder mass to the deltoid fascia, from just inferior to the mid-scapular spine directed laterally and inferiorly near the inferior border of the posterior deltoid. The deltoid muscle was gently elevated from distal to proximal, without detaching its origin or insertion, and the mass was identified (Fig. 2b). A circumferential marginal dissection was performed, and the mass was excised en bloc (Fig. 2c) and sent to pathology. The empty lateral fossae and prominent scapular spine highlighted the medial displacement and atrophy of the infraspinatus and supraspinatus muscles (Fig. 2d). After routine wound closure and dressing, the patient was awakened from anesthesia, transferred to the recovery room in stable condition, and discharged home as an outpatient.

Pathology
The mass consisted of partially encapsulated yellow fatty lobulated tissue measuring 9 cm x 11 cm x 2.5 cm (Fig. 2c) and composed of mature noninflammatory adipose tissue consistent with a benign lipoma. The entire specimen was inked, and sectioning displayed a yellow fatty lobulated cut that was grossly unremarkable. Figure 3 depicts the histology on H&E staining.

Recovery
The patient's recovery was uneventful and uncomplicated. She wore a simple sling as needed for comfort and transitioned to using the right arm as tolerated for activities of daily living. She enrolled in supervised physical therapy for active range of motion and strength training and continued physical therapy and home exercises for 6 months. Active forward elevation and abduction improved to 150 and to 110 , respectively. Active external rotation remained at neutral and passive external rotation was to 20 . Supraspinatus and infraspinatus muscle atrophy persisted. Deltoid strength was maintained but external rotation strength remained limited at 3/5. She rated her shoulder pain as 3/10 and assessed her shoulder function with an ASES score of 67 and Simple Shoulder Test of 10. She declined repeat MRI.

Discussion
Lipomas are benign fatty tumors most commonly observed around the shoulder and thigh. 10,11 Deep-seated or subfascial lipomas, such as intermuscular or intramuscular lipomas, are rare, 11 accounting for about 2% of all lipomas 5 . Intermuscular and intramuscular lipomas between and within the rotator cuff muscles, including supraspinatus, 4,7 infraspinatus, 9,14 and subscapularis 8 have been described. The clinical and imaging characteristics of subfascial lipomas may resemble those of well-differentiated liposarcomas, which confounds the differential diagnosis 11 and supports confirmatory excisional biopsy, especially in patients with symptomatic tumors. Subfascial lipomas around either or both of the spinoglenoid and suprascapular notch may compress the suprascapular nerve and cause weakness. Other more common causes of suprascapular nerve entrapment include spinoglenoid and suprascapular notch morphology, taut ligaments, bony excrescences, and ganglion cysts related to a chronic superior or posterior labrum tear. 1,15 Our patient presented with severe pain and weakness, most likely related  to compression by the lipoma of the suprascapular nerve and axillary nerve, especially the branch to the teres minor muscle. Others have previously reported on patients with shoulder pain and weakness resulting from intermuscular and intramuscular lipomas. 4,7,9,16e18,20 In some cases, the symptoms related to nerve compression, as appeared to be the case for our patient, whereas in others, the symptoms mimicked shoulder impingement. Ferrari et al reported on a 45-year-old man with symptoms, attributed initially to subacromial impingement, that abated after excision of a 5-cm intramuscular supraspinatus lipoma through an open posterior approach. 4 Relwani et al reported on a 52-year-old woman whose similar symptoms resolved after excision of a 5-cm subacromial lipomatous mass compressing the rotator cuff. 16 Park et al reported on a 49-year-old woman with an intramuscular infraspinatus lipoma causing subtle positional pain without obvious nerve compression. 14 In addition, several reports have described lipomas around either or both of the suprascapular and spinoglenoid notch causing direct suprascapular nerve compression. 7,9,20 Hazrati et al reported on a 50-year-old man presenting with deltoid referred pain and modest motion deficits. An MRI revealed a lobulated homogeneous mass at the suprascapular notch and EMG revealed suprascapular nerve compression. Symptoms resolved after open mass excision and suprascapular neurolysis and ligament release. 7 Kim et al reported on a 61-year-old man with shoulder pain and weakness suggesting a rotator cuff tear, but with an MRI demonstrating a 9.3 x 3.2 x 4.3 cm lipomatous mass at the spinoglenoid notch with evidence of suprascapular nerve compression. Shoulder strength and function recovered after marginal excision and spinoglenoid notch exploration through a posterior deltoid approach. 9 We chose a single-stage en bloc resection without preoperative biopsy because the MRI demonstrated a mass with benign features. In addition, we did not obtain a right upper extremity EMG preoperatively because it would not influence surgical decision-making given our patient's severe pain, shoulder weakness, and MRI findings.
Arthroscopy has been combined with open excision of subfascial shoulder lipomas to treat concurrent shoulder pathology. 2,6,7, 13 We did not entertain arthroscopy for our patient because plain radiographs, MRI, and physical examination did not demonstrate any obvious rotator cuff disease or intra-articular pathology. Others have raised similar concerns regarding concurrent arthroscopy. 4 Our 87-year-old patient is considerably older than others reported to have undergone rotator cuff muscle lipoma excision. Despite her advanced age, she experienced chronic severe right shoulder pain and dysfunction that were refractory to various nonoperative treatments and chose surgery because she did not want to suffer indefinitely. Although her improvements in comfort and function are more modest than those described elsewhere, the improvement in pain levels from 9/10 to 3/10 and the 50-point improvement in ASES score validate our decision to proceed with surgical excision.

Conclusion
This case serves as a reminder that not all older patients presenting with insidious onset pain and weakness have symptoms related to rotator cuff tears or arthritis. An intermuscular or intramuscular lipomatous tumor of the supraspinatus and/or infraspinatus should be considered in the differential diagnosis of the older patient presenting with insidious onset shoulder pain, progressive weakness, and loss of active elevation and external rotation, especially when there is no crepitance, plain radiographs are unremarkable, and a rotator cuff tear is not apparent by ultrasonography or MRI.

Disclaimer
The authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article.