Aphonsus is a 65-year-old professional violinist who presents with a lump on the radio-volar aspect of the interphalangeal joint of his right thumb (see picture).
It has been present for six months and is slowly getting bigger. It is uncomfortable and is most noticeable when typing, unscrewing jars and after long orchestral rehearsals.
He is otherwise in good health and his recent cardiovascular risk checkup was normal. His only medication is ibuprofen 200mg that he takes prophylactically before rehearsals and concerts.
The interphalangeal joint shows signs of osteoarthritis. The adjacent lump measures 30x16mm, is hard, minimally mobile and does not transilluminate.
What is the most likely diagnosis?
Correct!
A tenosynovial giant cell tumour (TGCT) is a rare mesenchymal neoplasm that develops from the synovium of a joint or the tendon sheath.
The vast majority of these lesions are benign, but locally aggressive. There are two forms of TGCT, nodular (also known as localised) and diffuse.
Nodular forms are more common, and usually present as a single, often painless, mass lesion, evolving over years, typically involving small joints of the hand and wrist. The diffuse form presents with more rapid onset of pain, swelling and reduced range of movement, typically of the knee, hip or ankle.
Nodular TGCT is often misdiagnosed clinically and even ultrasonographically as a ganglion, as it was by a reporting radiologist in this case. MRI is the most sensitive diagnostic modality.
Treatment of nodular TGCT is typically surgical removal with the aim of preventing recurrence of the tumour by meticulous dissection around the area of the tendon sheath or synovium from which the tumour has risen.
Localised nodular TGCT typically has a low relapse rate following complete excision, but recurrence may occur in those with diffuse or intra-articular disease.
Ganglions are usually softer and transilluminate. Tendon xanthomas are subcutaneous deposits of lipids seen in association with hyperlipaemia. Bouchard’s nodes affect the proximal interphalangeal joints and like Heberden’s nodes are due to osteoarthritis.
In this case, Alphonsus is referred to a hand surgeon for definitive treatment, with the operative findings confirming the diagnosis of TGCT. He has the stitches removed two weeks postoperatively and attends a hand clinic for supervised exercises to improve strength and range of motion around the thumb.
He resumes playing with the orchestra three months postoperatively, with no further complaint.