Photography

Musculoskeletal system
Case TypeClinical Case
Authors
Mikel Elgezabal, Constanza Elizabeth Garrido, Borja Canteli
Patient85 years, female
An 85-year-old woman with no significant past medical history presented with a rapidly growing mass on her left shoulder (Figure 1), with no history of trauma. On physical examination, the mass was hard and non-mobile.
A shoulder X-ray and ultrasound scan were performed in order to rule out malignancy.
The X-ray (Figure 2) shows a rounded, homogeneous soft-tissue density mass on the left shoulder, located just above the acromioclavicular joint (ACJ). Additionally, the humeral head is seen cranially displaced, with subsequent narrowing of the subacromial space. Osseous degenerative change can be seen in both the humeral head and the ACJ.
On the US exam (Figures 3a, 3b, and 3c), the images show a supraclavicular fluid collection, predominantly anechogenic but heterogeneous, that appears to be erupting superiorly from the acromioclavicular (AC) interval. No Doppler signal is detected. On interrogation of the rotator cuff, the exam shows the absence of the supraspinatus and infraspinatus tendons over the humeral head, as well as bony contour irregularity.
With the presumptive diagnosis of an acromioclavicular cyst secondary to a chronic massive rotator cuff tear, a percutaneous drainage was performed for symptom relief. After cytological analysis, no malignancy was detected, with cellularity (macrophages and lymphocytes on a proteinaceous background) consistent with the diagnosis of a cyst.
Acromioclavicular joint (ACJ) cysts are fluid-filled sacs that form adjacent to the ACJ, often due to underlying degenerative joint disease or rotator cuff tears. These cysts typically result from the extrusion of synovial fluid through a disrupted ACJ joint capsule, leading to pseudocyst formation [1].
Patients typically present with a visible or palpable swelling over the AC joint, along with discomfort or localised pain. The main clinical problem arises from differentiating these cysts from other soft tissue masses [1]. Imaging is crucial to confirm the presence of a cyst and to assess any underlying joint pathology. It is important to convey whether there is evidence of severe AC joint degeneration, rotator cuff damage, or communication between the joint and the cyst.
Ultrasound is typically the first-line imaging modality, allowing visualisation of the cyst and surrounding structures. Key findings include a well-defined, anechoic or hypoechoic mass near the AC joint, although this may not always be the case, as some cysts may show a heterogeneous appearance due to bleeding, infection, or proteinaceous content, as was our case. Ultrasound may also show communication between the joint and the cyst, which confirms its synovial origin (a feature known as “geyser sign” [2] (Figure 3). The absence of internal Doppler signals (Figure 3a) can also be key in ruling out an underlying solid mass. Besides, a fast growing pace (as in the case presented), makes malignancy more unlikely.
MRI is also valuable, particularly when assessing for concurrent rotator cuff tears or AC joint degeneration. X-ray can also be helpful to define the relation of the mass to bony structures and can provide indirect rotator cuff information, with humeral head cranial displacement and subacromial space narrowing often seen in massive cuff tears [3] (Figure 1). Biopsy is rarely necessary for diagnosis.
The treatment of AC joint cysts is typically conservative, focusing on alleviating symptoms by draining the cyst. Recurrence is common unless underlying joint pathology is addressed. In cases where the cyst is large, surgical options may be considered, which often involve resecting the cyst and repairing the joint. The prognosis depends on the severity of the underlying joint condition.
Written informed patient consent for publication has been obtained.
[1] Tshering Vogel DW, Steinbach LS, Hertel R, Bernhard J, Stauffer E, Anderson SE (2005) Acromioclavicular joint cyst: nine cases of a pseudotumor of the shoulder. Skeletal Radiol 34(5):260-5. doi: 10.1007/s00256-004-0883-6. (PMID: 15723212)
[2] Craig EV (1984) The geyser sign and torn rotator cuff: clinical significance and pathomechanics. Clin Orthop Relat Res 191:213-15. (PMID: 6499313)
[3] Cooper HJ, Milillo R, Klein DA, DiFelice GS (2011) The MRI geyser sign: acromioclavicular joint cysts in the setting of a chronic rotator cuff tear. Am J Orthop (Belle Mead NJ) 40(6):E118-21. (PMID: 21869946)
URL: | https://www.eurorad.org/case/18838 |
DOI: | 10.35100/eurorad/case.18838 |
ISSN: | 1563-4086 |
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