Table 1 D-TGCT Knee MRI structured report template

1. Shape

Well-circumscribed nodules and /or diffuse villous synovial thickening

2. Site

2a. Intra-articular

Anterior compartment (suprapatellar, superior and inferior infrapatellar recesses)

Middle compartment (central, femorotibial, intercruciate recesses)

Posterior compartment (retrocondylar, PCL, subpopliteus, Baker’s cyst)

Cartilage and bone invasion by the tumour (tumour extension in pressure erosions)

2b. Extra-articular

Posterior transcapsular extension to popliteal fossa

Muscular-tendinous involvement (invasion or encasement > 180°)

Ligament involvement (invasion or encasement > 180°)

Neurovascular bundle involvement (> 180° encasement of the tibial nerve and/or popliteal artery/veins)

3. Signal intensity

T1-WI: (hypo-/isointense) and (homogeneous/heterogeneous)

T2-WI FS: (hypo-/iso-/hyperintense) and (homogeneous/heterogeneous)

T1-WI FS Gd: enhancement (absent/present) and (homogeneous or heterogeneous)

T2*-WI or T1 GRE: blooming (absent/present)

4. Size

Bidimensional measurements [RECIST 1.1: long axis of target lesions, modified RECIST: long and short axis of target lesions]

Volumetric tumour burden (Tumour Volume Score)

5. Secondary findings (complications)

Joint Effusion (> 10 mm anteroposterior in the suprapatellar pouch)

Reactive synovitis (sometimes fatty metaplasia, hyperintense on T1-WI)

Secondary osteoarthritis/Chondromalacia

Conclusion

Subtype (growth pattern)

Diffuse-type TGCT (≥ 2 synovial recesses)

Extension

Intra-articular and/or extra-articular

Complications

Secondary osteoarthritis (mild, moderate, severe)