INTRODUCTION
Extra-articular, intramuscular ganglion cyst is an uncommon differential diagnosis to be strongly considered for cystic lesions in the popliteal fossa. It typically presents as a painless slow-growing mass. These cysts rarely become painful or symptomatic. The exact etiology for a painful ganglion is unknown. However, from various studies reporting on ganglion, the most likely conclusion is that pain, even when present, is more likely to be annoying rather than debilitating.[1] Here, we present a case of surgical excision of the “symptomatic” ganglion cyst along with arthroscopic management of intra-articular derangements as a sound treatment option with no recurrence.
CASE REPORT
A 52-year-old male presented with a nontraumatic dull-aching pain in his left knee for the past 10 years. On examination, knee range of motion was 0°–100° with further 10° of painful passive flexion possible. There was mild tenderness in the lower part of popliteal fossa; however, no cyst could be clinically appreciated. McMurray's test for medial meniscus appeared to be strongly positive. A 1.5 Tesla magnetic resonance imaging (MRI) revealed a well-defined, multilobulated T2 and proton density (PD) hyper-intense collection (~8.3 cm × 3.7 cm × 3.0 cm) involving the medial head of gastrocnemius, insinuating between fibers of popliteus and medial head of gastrocnemius [Figure 1a-c]. A complex tear involving posterior horn of medial meniscus and Grade II chondromalacic changes involving medial and lateral facet of retropatellar cartilage was also noted. Under general anesthesia and tourniquet control, the patient was placed in prone position. Through a lazy S incision in the popliteal fossa, a large multilobulated cyst measuring 7 cm × 3.5 cm × 3 cm was found confined within the muscle fibers of medial head of gastrocnemius which was excised en masse [Figure 2]. There was no communicating aperture extending into the joint. The patient was re-positioned in supine, and arthroscopic medial meniscal balancing was accomplished. The specimen consisted of a single multiloculated cyst, and the cut section showed smooth inner wall with mucoid material. Histopathological assessment revealed a fibrotendinous cyst lined by a thin epithelium and the walls showed myxoid degeneration, perivascular lymphoplasmacytic infiltrate, muscle fibers, and adipose tissue, all consistent with the diagnosis as ganglion cyst [Figure 3]. Postoperatively, the patient was encouraged quadriceps strengthening exercises and prescribed chondroprotective agents. At 18 months of follow-up, there is no recurrence of the swelling and the International Knee Documentation Committee score of his left knee is 79.3.
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Figure 1: (a) Sagittal section well-defined T2-weighted hyperintense multiloculated collection involving the medial head of gastrocnemius; (b) sagittal section T1-weighted sequence, it appears as isointense in comparison with surrounding muscles; (c) axial section proton density fat-saturated collection suggestive of cystic lesion
Figure 2: Intraoperative image showing the ganglion cyst in the popliteal fossa found within the muscle fibers of the medial head of gastrocnemius (Inset: excised single multilobulated cyst filled with a mucoid material contained within a thin fibrous capsule)
Figure 3: Section showing fibrotendinous cyst focally lined by attenuated epithelium containing muciphages (10 X -low power, H and E stain)
DISCUSSION
A ganglion is a juxta-articular benign well-encapsulated cystic lesion containing a gelatinous fluid. Ganglion cysts are most commonly encountered about the wrist joint. In the knee joint, they are differentiated as intra-articular or extra-articular (intramuscular, perineural, intraosseous, or periosteal). Ganglion cysts are thought to arise from the myxoid degeneration of connective tissue associated with a joint capsule or tendon sheath and therefore lack a true cell lining.[2] The etiology of intramuscular formation of ganglion cyst is unclear. They are usually small and rarely become symptomatic. On many occasions, they are just an incidental finding in imaging studies that are undertaken for other intra-articular pathologies. Clinically, it may not be possible to differentiate diverse cystic lesions of the popliteal fossa, and thus, MRI is the investigation of choice. Common differential diagnosis includes the baker cyst, parameniscal cyst, popliteal artery aneurysms, myxoid tumors, and intramuscular collections (hematoma/abscess).
To differentiate these juxta-articular masses, imaging studies can include either arthrography, ultrasonography (USG), computed tomography (CT), or MRI. The main objectives of these imaging techniques are as follows: to confirm the cystic nature of the lesion; to determine whether there is a communication between the cyst, the joint cavity, and the surrounding structures; and finally, to evaluate the nearby joint for associated disorders.[3] Arthrography, though infrequently used nowadays, is one of the accurate methods to differentiate the cystic masses in the popliteal fossa between communicating and noncommunicating types. In USG, both ganglion cysts and synovial cysts appear as anechoic or hypoechoic masses and uni/multiloculated with or without septations. However, sonocompressibility is a criterion that can be very helpful to differentiate a synovial cyst, normally more easily compressible, from a ganglion cyst, much harder to compress due to its thick, viscous content, and its dense fibrous capsule.[3] In CT scans, the cyst may appear as a hypodense (multiloculated) lesion within the isointense muscle. Further, in CT scans, the location, extent, and multiloculation of lesion suggest that cyst did not originate from any of the bursae (differentiating it from the synovial cysts).[4] In MRI studies, ganglion cyst presents as well-defined rounded or lobulated fluid collections with sharply defined internal septations (“bunch of grapes appearance”).[5] On T2-weighted and PD sequence, ganglia appear hyperintense, and on T1-weighted sequence, they appear as hypointense/isointense in comparison with the surrounding muscles.
In majority of instance, ganglion cyst can be managed conservatively. James et al. reported a series of ten cases, all of which were incidental findings in MRI and were managed conservatively.[6] On the other hand, when these cysts enlarge and become painful or affect activities of daily life, surgical excision can be contemplated. Nicholson and Freedman reported a case of intramuscular dissection of a large ganglion cyst into the gastrocnemius muscle that warranted surgical excision.[7] Similarly, Han et al. reported a case of intramuscular ganglion that presented as a swelling in the popliteal fossa that was increasing in size and painful on palpation and underwent surgical excision for the same.[8] Recently, Ju et al. described an ultrasound-guided (aspiration and steroid injection) therapy for symptomatic lower extremity ganglion cysts, which included a single case of ganglion involving the posterior aspect of the knee.[9] A long-term follow-up is essential to understand the potential of this therapy, especially with respect to recurrence. However, it appears to be an effective means of treatment for patients who are unfit for surgery. In the index case, owing to overlapping clinical symptoms, surgical option was considered for both ganglion cyst and concomitant complex tear of posterior horn of medial meniscus. This is perhaps the first case where both the lesions described (medial meniscus tear and ganglion cyst) have been treated surgically with good clinical outcomes.
This case highlights the clinical condition of a rare enlarged symptomatic extra-articular ganglion cyst within the medial head of gastrocnemius. It is important for the clinicians and radiologists to distinguish different types of cystic lesions arising in the popliteal fossa. Either USG or MRI can be undertaken for ascertaining the lesion; however, ganglion cyst has characteristic MRI appearances that can aid in accurate diagnosis. Surgical excision of the “symptomatic” ganglion cyst along with arthroscopic management of intra-articular derangements is a sound treatment option with low recurrence rate.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
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Conflicts of interest
There are no conflicts of interest.
REFERENCES
1. Gude W, Morelli V. Ganglion cysts of the wrist: Pathophysiology, clinical picture, and management Curr Rev Musculoskelet Med. 2008;1:205–11
2. Kumar V, Abbas A, Fausto N, Aster J. Bones, joints, and soft-tissue tumors Robbins and Cotran Pathologic Basis of Disease. 20108th Philadelphia, PA Saunders, Elsevier:1247
3. Giard MC, Pineda C. Ganglion cyst versus synovial cyst? Ultrasound characteristics through a review of the literature Rheumatol Int. 2015;35:597–605
4. Lee KR, Cox GG, Neff JR, Arnett GR, Murphey MD. Cystic masses of the knee: Arthrographic and CT evaluation AJR Am J Roentgenol. 1987;148:329–34
5. Perdikakis E, Skiadas V. MRI characteristics of cysts and “cyst-like” lesions in and around the knee: What the radiologist needs to know Insights Imaging. 2013;4:257–72
6. James SL, Connell DA, Bell J, Saifuddin A. Ganglion cysts at the gastrocnemius origin: A series of ten cases Skeletal Radiol. 2007;36:139–43
7. Nicholson LT, Freedman HL. Intramuscular dissection of a large ganglion cyst into the gastrocnemius muscle Orthopedics. 2012;35:e1122–4
8. Han HH, Kim JM, Moon SH. A cystic mass in the popliteal fossa and its differential diagnosis Arch Plast Surg. 2015;42:484–6
9. Ju BL, Weber KL, Khoury V. Ultrasound-guided therapy for knee and foot ganglion cysts J Foot Ankle Surg. 2017;56:153–7
