Tenosynovial giant cell tumor
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Tenosynovial giant cell tumors (GCT), also known as tenosynovial tumors of tendon sheath, are a group of so-called fibrohistiocytic tumors, 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 tumor is the unifying term used in the 2020 WHO Soft Tissue and Bone Tumors Classification (5th ed.) with giant cell tumor of tendon sheath also acceptable 1. They have previously been known as pigmented villonodular tumor of the tendon sheath (PVNTS), extra-articular pigmented villonodular tumor of the tendon sheath, or localized/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 tumors (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 etiology of tenosynovial GCT is unknown 1. The WHO classification classes this tumor into subtypes by growth pattern (localized-type vs diffuse-type) and location (intra-articular vs extra-articular) 1. Localized 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, hemosiderin deposition, and stromal collagenisation in different tumors 1. In the localized-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 tumors can occur 9. Metastases can occur, even from benign tumors, 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 tumor 7
calcification, in essence, excludes the diagnosis of tenosynovial giant cell tumors ref
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