Ganglia are common throughout the wrists and the hands.
There are discussed under their own section here
Giant cell tumour of the tendon sheath represents a synovial metaplastic condition equivalent to extra-articular pigmented villonodular synovitis (PVNS). The tumour is most commonly encountered in the hands and feet, in close association with an adjacent tendon. On ultrasound the mass appears to be lobulated well demarcated generally without calcification and associated with increased blood flow on Doppler assessment. The location of the tumour and its relation to the adjacent tendon is its most characteristic feature. On MRI, the lesions exhibit areas of low signal on T2 weighting reflecting their haemosiderin content. It should be appreciated that a degree of low signal is proportional to haemosiderin content and therefore lesions with less or no haemosiderin may not demonstrate this feature. Conversely, other lesions contain considerable haemosiderin and may appear diffusely black on T2 weighting. In these instances, the differential diagnosis includes tumours of fibrous aetiology. Once again the characteristic location is an important to diagnosis. The commonest soft tissue masses in the wrist and hand are ganglions and fibroma’s. Many of these do not come to imaging. The principal differential diagnosis of larger lesions that do come to imaging that include PVNS is neurilemmoma. Neurilemmoma tends to occur proximal to the level of the metacarpal phalangeal joints whereas PVNS tends to be distal. In most cases of Neurilemmoma lie in the path of reasonable sized nerve structures and the innovating nerve can usually be detected particularly on axial T1 weighted imaging. Examples of this tumour are included in another section. Giant cell tumours of the tendon sheath are also often encountered in the forefoot. The differential diagnosis of a soft tissue tumour containing material of low signal includes fibroma, fibromatosis, melanoma and amyloidoma.
Second
Fibroma is a term used to describe a mass that comprises dense connective tissue usually due to proliferation of fibroblasts. In the wrist and hand, they more commonly arise as a consequence of chronic mechanical irritation of ligaments and other connective tissue structures rather than a true neoplasm. They are particularly common in relation to the superficial fascia and the flexor pulleys. They cause symptoms either by their Mass effect, by causing contracture leading to finger flexion or buy a triggering effect on adjacent tendons. Because of the nature of the lesion, they tend to be low signal intensity on most MR sequences. On ultrasound, the principal clue is the relationship between the mass and the fibrous structure from which it arises. The internal structure easier to see on ultrasound than on MRI though this has little impact on diagnosis. The commonest sites of involvement are the superficial fascia which is referred to as Dupytrens contracture. This may also be associated with plantar fibroma.Fibromas of the flexor pulley system usually present as a consequence of the impact they exert on the adjacent flexor tendon. Pain may be the presenting complaint however as the tendon becomes irritated and begins to swell, a clicking sensation may be palpated as the swollen tendon nodule moves onto the fibroma. In time, with disease progression, the tender nodules may eventually become locked underneath the fibroma resulting in the classical trigger finger. Dynamic ultrasound examination is the best way of demonstrating this. Ultrasound has also been used to guide steroid injection or division of the pulley itself
A Neurilemmoma is a tumour of the nerve sheath. This lesion is also referred to as the Schwannoma. They are benign lesion predominantly and can arise from any nerve trunk including the intramuscular nerves. In most cases, the nerve from which they arise is easily identified particularly on axial T1 weighted images or ultrasound. On MRI, a fusiform lesion is characteristic. The lesion will have intermediate signal on T1 with increased signal on T2. The nerve can be seen entering the lesion at one end and leaving at another. The bulbous tumour and its attached nerve are sometimes referred to as the spring onion sign or the comet tail sign. The tumour can often be identified lying eccentric with the nerve passing around the periphery. Within the lesion, mixed high signal is characteristic on T2 weighted images. Areas of necrosis or cyst formation may be seen. Gadolinium is rarely required but diffuse enhancement other than areas of necrosis or cyst formation is characteristic. Malignant change may occur within a neurilemmoma and rapid growth and associated increasing pain should raise suspicion of a malignant Schwannoma. In some cases the lesions may slowly grow to giant size with large areas of central necrosis and haemorrhage. This is termed an ancient Schwannoma which is not a malignant lesion. In the hand and wrist the commonest area to find Neurilemmoma is of the median nerve particularly of its branches just distal to the carpal tunnel. Along with other signs, the location of the lesion provides a useful differentiation from giant cell tumour in that Neurilemmoma tend to occur proximal to the metacarpal phalangeal joint level whereas giant cell tumour tends to be distal. Exceptions are well known however.
On ultrasound the lesions are generally of low reflectivity but within obvious complex internal structure. Very occasionally the low signal can be misdiagnosed as a cyst, however this is less common on moderA n equipment. If necessary, the ultrasound gain can be increased to demonstrate the internal structure. Areas of necrosis and cyst formation are also readily detected on ultrasound as well as increased vascularity within the lesion. The nerve from which the lesion arises is usually also easy to detect on ultrasound. A dilated tube can be seen entering the nerve and leaving at the distal end. Doppler study will demonstrate that the intervening tube comprises not only the nerve but also the perineural vessels particularly perinerual veins that may be dilated by the tumour. An additional useful sign present on ultrasound is that compression with the ultrasound probe may induce a tingling sensation similar to the clinical Tinel’s sign. Ultrasound can also be used to biopsy these lesions however caution needs to be exerted if Tinel’s sign is positive. If there is a strongly positive Tinel’s then biopsy without regional anaesthesia is unlikely to be straight forward. Applying local anaesthetic around the nerve may help in some cases. Caution should also be exerted in patients with a negative Tinel’s sign and a careful assessment of the capsule of the lesion should be made with the anesthetising needle prior to plunging a biopsy needle directly into the tumour.
Characterised by mixed fat and soft tissue signal with a lobulated margin. May have prominent surrounding vessels.
Lipoma is one of the easiest tumours to diagnose using MRI. There are relatively few tissues which have increased signal arm T1 weighted images without enhancement. The rest is a common sight for life, where it can present either as a soft tissue mass or by exerting mechanical effects including neural compression and trigger finger. Rare variants include hibernoma and sclerotic lipoma
