Clinical History
A 24-year-old male athlete presented with an oedematous appearance of the dorsal surface of his right foot.
Imaging Findings
A 24-year-old male athlete presented with a painful, reddish, oedematous lesion on the dorsal surface of his right foot. The lesion started to grow after a long-lasting and tiring training. The lesion showed no tension and no tethering to the adjacent tissues.
The MRI revealed the presence of a cystic lesion on the dorsal surface of the foot, in close proximity to the tendon of the digitorum longus extensor muscle. The lesion showed thickened margins, with peripheral enhancement after the intravenous administration of paramagnetic substance and measured 1.5 mm in its biggest diameter. The soft tissues around the lesion also showed enhancement, a sign of accompanying inflammatory reaction. A communication between the lesion and the articular cavity was not proven.
MRI also revealed an increased amount of articular fluid among the bones of the right tarsus.
The MR characteristics and location of the lesion are compatible with a ruptured ganglion cyst.
Discussion
Ganglion cysts represent one of the most common, benign, soft-tissue masses. A ganglion is a cystic mass, with a dense fibrous connective tissue capsule, lined with discontinuous, flat, spindle-shaped cells, probably representing an advanced stage of a degenerated synovial cyst [4,5]. It is usually found in periarticular soft tissues in areas under repetitive stress, such as the joint capsule or tendon. Patients are either asymptomatic, or present with pain or palpable mass; a history of trauma is elicited in 10% of the cases [2].
The cause of ganglia remains controversial. The most probable theory suggests that stretching of the capsular and ligamentous structures stimulates mucin production, which then dissects through these structures, forming capsular ducts and lakes that coalesce into a main cyst [2]. Most cysts contain a highly viscous clear jellylike fluid (“gelée de pomme”) [3, 1]. Adherence of ganglion cysts to arteries and nerves is frequent. Their communication with the articular cavity is not constant, but it should always be looked for [3,5].
MRI has been traditionally used to characterise these lesions; ganglia appear with an intermediate to high signal intensity on T1WI (due to their increased accumulation of mucopolysaccharides) and a markedly high signal intensity on T2WI. Although ganglia have been mostly described as simple or well-circumscribed cystic lesions, many of them are complex and do not fulfil the criteria for a simple cyst. Hypoechogenicity, septations, lobulations and ill-defined walls are sonographic findings of atypical, complex ganglia that have been described in a large series of patients [2].
The most common complications associated with ganglion cysts are haemorrhage, trauma, infection and rupture.
In particular, a ruptured ganglion cyst typically presents with irregular margins and an accompanying inflammatory reaction of the perilesional tissues and the subcutaneous fat. The cyst has thick walls and often presents with multiple lobules and septations. The lesion shows no clinical signs of tension and it resolves spontaneously under non-steroidal anti-inflammatory treatment [2]. The ruptured ganglion cyst should be differentiated from a deep venous thrombosis and a soft-tissue abscess. The differential diagnosis from the former is based on the results of the colour Doppler examination, whereas from the latter is based on the sudden onset of symptoms, the lack of tension above the lesion and the response to the anti-inflammatory treatment. Other entities that should be encountered in the differential diagnosis of a ruptured ganglion are synoviosarcomas, arterial aneurysms and cystic schwannomas [1].
Differential Diagnosis List
Ruptured ganglion cyst
Soft tissue abcess
Synovial cyst
Aneurysm
Cystic schwannoma
