Age / Sex : 38 / F

Chief complaint : Palpable mass on right ankle, for 2 years.

What is your diagnosis?

Two weeks later, you can see the final diagonosis with a brief discussion of this case (Please submit only one answer).

Courtesy : Ro-Woon, Lee, Inha University Hospital

Discussion

Tenosynovial giant cell tumor (TSGCT, localized type)

Findings:

1) Plain radiography

 Plain radiograph of right ankle shows suspicious ovoid shape soft tissue mass at posterior aspect of right ankle. No combined perilesional bone change is seen on this image. Also, small osteochondral lesion is seen at talar dome.

2) MR

T1- and T2-weighted axial MR images show isointense signal intensity mass lesion in intermuscular layer of right posterior ankle, compared with the skeletal muscles. This lesion is tightly abutting to lateral aspect, distal MT junction level of flexor hallucis longus muscle. Proton density fat saturated (PDFS) MR images show mixed signal intensity areas of mild hyper- to isointense signal intensity to adjacent muscles and some marked dark signal intensity areas. Mild hyper- to isointense signal intense areas within the mass show well enhancement, whereas dark areas on PDFS MR images did not show enhancement after the IV administration of contrast media. Some diffusion restriction is seen at peripheral aspect of the mass lesion on DWI image.

Differential Diagnosis:

pigmented villonodular synovitis (PVNS)

desmoid tumor

fibroma of the tendon sheath

complicated ganglionic cyst

Discussion:

Giant cell tumor of the tendon sheath comprises approximately 1.6% of all soft-tissue tumors and is characteristically a benign peritendinous fibrous mass. There is debate as to whether the tumor is a true neoplasm or a pseudoneoplastic inflammatory response to soft-tissue trauma. This hypervascular lesion arises from the synovium of the tendon sheath or synovial lining of joints or bursa and is characterized microscopically by synovial cells, histiocytes, multinucleated giant cells, inflammatory cells, macrophages, xanthoma cells, and collagen.

Both a localized and a diffuse form have been described. The localized form can arise in or extrinsic to a joint, and the diffuse form predominantly originates outside the joint. Grossly, giant cell tumor of the tendon sheath appears as a rubbery, multinodular, well-encapsulated, grayish tan, brown, orange, or yellow mass; the color depends on the proportion of foam cells and degree of hemosiderin deposition. A collagenous capsule surrounds the lesion

Characteristic MR imaging findings include the presence of fibrosis, which is manifested as areas of low signal intensity on all pulse sequences, and hemosiderin deposition, which results in blooming artifact on gradient echo images. The extent of the mass may be obscured by signal intensity similar to muscle on T1-weighted images. However, fibrosis and inflammatory cell infiltrate can result in varying degrees of enhancement, which aids in defining the extent of the tumor. The differential diagnosis includes any soft-tissue mass with low signal intensity on both T1-weighted and T2-weighted images, such as a desmoid tumor (particularly if deep) or pigmented villonodular synovitis, which more commonly involves the larger joints.

References:

Kang, H.S, Hong, S.H, Choi, J.-Y, Yoo, H.J. Oncologic imaging: Soft tissue tumors. Springer, 2017, p110-111.

Middleton WD, Patel V, Teefey SA et-al. Giant cell tumors of the tendon sheath: analysis of sonographic findings. AJR Am J Roentgenol. 2004;183 (2): 337-9. AJR Am J Roentgenol

Ly JQ, Carlson CL, Lagatta LM et-al. Giant cell tumor of the peroneus tendon sheath. AJR Am J Roentgenol. 2003;180 (5): 1442. AJR Am J Roentgenol

Jelinek JS, Kransdorf MJ, Shmookler BM et-al. Giant cell tumor of the tendon sheath: MR findings in nine cases. AJR Am J Roentgenol. 1994;162 (4): 919-22. AJR Am J Roentgenol

Murphey MD, Rhee JH, Lewis RB et-al. Pigmented villonodular synovitis: radiologic-pathologic correlation. Radiographics. 28 (5): 1493-518.