Tenosynovial giant cell tumours (GCT), also known as tenosynovial tumours of tendon sheath, are a group of so-called fibrohistiocytic tumours, which are usually benign, most often arise from the synovium of joints, bursae or tendon sheaths, and show synovial differentiation 1-5. Despite identical histology, there are two subtypes that have different clinical presentations and management and they are discussed separately 3,6:
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Terminology
Tenosynovial giant cell tumour is the unifying term used in the 2020 WHO Soft Tissue and Bone Tumours Classification (5th ed.) with giant cell tumour of tendon sheath also acceptable 1. They have previously been known as pigmented villonodular tumour of the tendon sheath (PVNTS), extra-articular pigmented villonodular tumour of the tendon sheath, or localised/focal nodular synovitis 11,12. Pigmented villonodular synovitis (PVNS) is no longer a recommended term per the 2020 WHO classification 1.
Diagnosis
Diagnostic criteria according to the WHO classification of soft tissue and bone tumours (5th edition) 1:
essential: intra- or extra-articular location; varying proportions of small histiocytic cells, large amphiphilic cells, foam cells, multinucleated giant cells
desirable: CSF1 rearrangement in selected cases
Pathology
The aetiology of tenosynovial GCT is unknown 1. The WHO classification classes this tumour into subtypes by growth pattern (localised-type vs diffuse-type) and location (intra-articular vs extra-articular) 1. Localised tenosynovial GCT is more common with a predominance for the hand and wrist whereas the diffuse-type is less common and affects the large joints (e.g. knee, hip, ankle) more 3.
Extra-articular tenosynovial GCTs are most commonly periarticular in the lower limb (particularly the knee) but can be intramuscular or subcutaneous in location 1.
Malignant tenosynovial GCTs are extremely rare with ~50 reported cases 1.
Macroscopic appearance
See the relevant subtypes for description.
Microscopic appearance
On microscopy the appearance is variable due to differening proportions of mononuclear cells, multinucleated giant cells, foamy macrophages, inflammatory cells, haemosiderin deposition, and stromal collagenisation in different tumours 1. In the localised-type osteoclast-like giant cells and xanthoma cells are usually frequent whereas in diffuse-type osteoclast-like giant cells are less frequent and often absent 1.
Genetics
CSF1 translocation 1
Treatment and prognosis
Surgery is the mainstay of treatment. Recurrence rates are higher in diffuse-type (~35%) compared to local-type (~17.5%) 1. Molecular therapy using CSF1 inhibitors is a potential treatment for unresectable or metastatic disease 1.
Locally aggressive and malignant tenosynovial giant cell tumours can occur 9. Metastases can occur, even from benign tumours, most commonly to lymph nodes and lung 1.
History and etymology
The term PVNS was first proposed by Jaffe et al. in 1949 9. The first description of the condition was by Chassaignac in 1852 who had described a nodular lesion of the synovial membrane that affected the flexor tendons of the fingers 8.
Differential diagnosis
On MRI, for low T2 signal masses without characteristic blooming artifact consider 7:
tendon sheath fibroma: no blooming on T2* sequences 11
nodular fasciitis: subcutaneous location 11
post-trauma change
Practical points
the absence of blooming artifact does not exclude tenosynovial giant cell tumour 7
calcification, in essence, excludes the diagnosis of tenosynovial giant cell tumours ref
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