A 70-year-old woman was seen for left anterolateral shoulder pain which had started one year ago after lifting a heavy furniture. During physical examination, restricted active shoulder flexion and abduction were observed due to aggravated pain. No focal swelling of her affected shoulder was noted. The pain worsened with activities of daily living, particularly when she raised her hand overhead. Plain radiographs of her left shoulder showed no remarkable findings. She was initially treated with non-steroidal anti-inflammatory drugs and physical therapy; however, these measures did not sufficiently alleviate her pain. Further investigation via ultrasound revealed a localized 5.1 × 2.5 × 1.9 mm anechoic cystic lesion with well-defined margins at the distal attachment of the subscapularis tendon. It moved during external and internal rotation of the shoulder, suggesting a ganglion cyst (Figure 1 and Video 1). No signs of rotator cuff or labral tear were detected.

Ganglion cysts are commonly encountered indaily musculoskeletal practice and are generally believed to result from the myxomatous degeneration of specific fibrous tissue structures [1]. The majority, around 70%–80%, develop on the hand or wrist [2]. The occurrence of a ganglion cyst in the shoulder is uncommon, usually found in specific areas such as the spinoglenoid and suprascapular notches [3]. Theprecise cause of ganglion cysts is still unknown, although theories propose that trauma, tenosynovitis, or a congenital anomaly may be responsible [4]. A previous study also reported the frequent occurrence of rotator cuff pathologies in conjunction with ganglion cysts [5].

Both ganglion cysts and bursal fluid collectioncan cause symptoms such as pain, weakness, swelling, or joint immobilization due to compression of nearby structures. However, there are distinct differences in their management. A symptomatic ganglion may require aspiration or surgical excision of the cyst itself [6]. In contrast, therapy for bursitis primarily focuses on treating the coexisting intra-articular disease as well as corticosteroid injection [7].

Ultrasound has become a widely used diagnostic tool for differentiating shoulder lesions. Both focal bursal fluid collection and ganglion cysts appear as anechoic to hypoechoic cystic lesions near joints or tendons. To distinguish between the two, compression using the transducer serves as a useful tool [8]. Bursal distention, containing synovial fluid, typically collapses upon compression, whereas a ganglion, with its viscous content and dense fibrous capsule, is notably non-compressible [9]. Another significant sonographic characteristic involves evaluating blood flow using Doppler imaging [8]. Ganglion cysts typically do not exhibit blood flow, whereas bursitis may display internal blood flow when intra-bursal synovium inflames. In terms of their configuration, ganglion cysts typically exhibit round or oval shapes, characterized by a multilocular or multilobular structure. They are well-defined and display homogeneity [9]. A distended bursa can manifest as either simple unilocular anechoic or more complex hypoechoic fluid collection [10]. As for the mobility, ganglion cysts in the shoulder are outpouchings of ligament or tendon sheaths and can move along with them [11]. On the other hand, the subdeltoid bursa is between the deep fascia of the deltoid muscle and the supraspinatus tendon. The main function is to reduce friction between adjacent moving structures [12]. Therefore, when there is focal fluid accumulation, it is expected to reside in bursal space during movements of the adjacent tendon [13].

In conclusion, this article highlights the diagnostic significance of ultrasound in identifying cysts associated with the subscapularis tendon and differentiating them from focal subdeltoid bursa accumulation.

Video 1. Subscapularis Ganglion Cyst
The video is available at http://doi.org/10.29760/APJP.202403/PP.0001.

Figure 1. Imaging for a Subscapularis Ganglion Cyst
(A) Ultrasound imaging of the left shoulder region revealed an anechoic, well-marginated cystic lesion (arrowhead) at the distal attachment of the subscapularis with the shoulder in a neutral position. (B) When the shoulder was moved to 90 degrees of external rotation, the cyst was observed to move along the tendon. (C) Upon the shoulder was moved to 70 degrees of internal rotation, the cyst was also observed to move along the tendon. The biceps tendon is marked with an asterisk. The transducer’s position was elaborated with blue square.

The authors declare no conflicts of interest

This work was funded by National Taiwan University Hospital, Bei-Hu Branch; Ministry of Science and Technology (MOST 106-2314-B-002-180-MY3 and 109-2314-B-002-114-MY3); and the Taiwan Society of Ultrasound in Medicine