Rare Lipoma of the Tendon Sheath of the Fifth Extensor Compartment of the Hand

Lipoma of an extensor tendon compartment is an extremely rare tumour of the hand. Although benign, it can cause pain, finger stiffness and nerve compression, necessitating surgical excision.

As patients frequently present to Hand Therapists for an opinion and symptomatic management; it is important that therapists are aware of the existence of lipoma’s and their treatment, so as to not delay referral to a hand surgeon for surgical release and histological examination.

Case Study:

David, a 49 year old man presented to Hand Therapy with an 8 month history of a lump on the dorsum of the left hand between the 4th and 5th Metacarpals. The lump was causing pain and stiffness of his ring and little fingers. He had also developed a neuropraxia and was unable to bring his little finger in towards his hand.

A hard, mobile lump could be felt on the back of his hand between the metacarpals of the little nad ring finger (4th webspace).

David was referred for radiographs, an ultrasound scan and nerve conduction studies. The radiograph was unremarkable but the ultrasound scan revealed a highly vascular mass as well as bony erosion of the 5th MCP joint. Sonar is very sensitive to the presence of such leaions, but is non-specific to the aetiology of the lesion. Therefore several differential diagnoses were possible, including both benign and malignant possibilities.

The first image shows the tumour and bony erosions of the MCPJ and the second image shows the highly vascularised tumour.

Results:

The nerve conduction study confirmed Cubital Tunnel Syndrome, with a recommendation for surgical release. The nerve compression was the reason the patient could not adduct his little finger towards his ring finger.

David was referred to Dr Andrew Barrow to have the mass removed. The mass was sent for a histological analysis which confirmed a rare lipoma of the tendon sheath of the 5th extensor compartment.

David returned to hand therapy 1 week after surgery. Scar tissue had started to develop around the surgical incision. Some pain and finger stiffness was present. The nerve compression had resolved and finger adduction becam possible again.

Discussion:

Lipomas of the tendon sheath are rare, with only a few reported cases. To our knowledge only one other case of a lipoma in the 4th extensor compartment of the hand has been reported by Gurich et al in the American Journal of Orthopaedics in December 2015.

According to Gurich et al, there are 2 types of Lipoma’s; eother a discrete solid masses of adipose tissue or adipose tissue coupled with hypertrophic synovial villi. Both types are benign but require surgical excision because they cause symptoms of pain, stiffness and nerve compression.

Although Lipoma’s are benign by definition, they can transform into liposarcoma’s in rare cases (Murphey et al, 2004). Recurrence rates are less than 5% if complete surgical excision of the lipoma occurs. It is important that clinicans are aware of the dangers of Lipoma's and promptly refer for surgical excision.