Case Summary

A 63-year-old man presented with a long-standing soft-tissue mass at the volar aspect of his right proximal interphalangeal (PIP) joint that had recently become increasingly irritating, but without significant increase in size. Physical examination revealed a firm, fixed subcutaneous nodule, causing limited flexion at the right fourth PIP joint, but without loss of sensory or overall function of the hand. There was no significant tenderness, and no other nodules were identified. A retinaculum cyst was suspected and, following radiography (Figure 1), a magnetic resonance (MR) imaging study was obtained for further evaluation (Figure 2). Figures 1 through 4 are images obtained prior to histologic confirmation.

Figure 1

Figure 2

Diagnosis

Giant-cell tumor of the tendon sheath

Imaging Findings

Although not impressive or specific in appearance, the soft-tissue density identified radiographically over the fourth right PIP joint is certainly abnormal, prompting further characterization with cross-sectional imaging. The magnetic resonance (MR) imaging study revealed a well-defined soft-tissue mass arising from the flexor tendon sheath of the finger (Figure 2); the mass had the appearance and signal characteristics of a giant-cell tumor of the tendon sheath. Histologic examination confirmed the diagnosis. The tumor was excised on clinical grounds alone.

Figure 3

Figure 4

Discussion

Giant-cell tumors are common bone tumors, usually occurring at the epiphyses of long bones. These tumors have also been known to occur less commonly in soft-tissue form, known as giant-cell tumors of the tendon sheath (GCTTS). As its name implies, the tumor arises from the tendon sheath and includes discrete, nodular, or polypoid masses commonly affecting the digits of the hands1 and feet; involvement is usually extra-articular but can occur intra-articularly as well. There is also a more diffuse and irregular form, known as proliferative or florid synovitis. Less common than the nodular form, the diffuse type occurs exclusively outside of a joint space.² Common sites of occurrence for the diffuse form are the ankle and knee. Neither type of GCTTS have been known to metastasize or are associated with malignancy, as has been reported in 20% of giant-cell tumors of bone.³

Giant-cell tumors of the tendon sheath can resemble pigmented villonodular synovitis (PVNS) histologically, but are distinguished clinically by the numerous frondlike villous masses associated with diffuse intra-articular synovial involvement of PVNS. Additionally, PVNS is associated with the deposition of large amounts of hemosiderin, involves the hips and knees, and causes large joint effusions. The treatment of PVNS almost always requires aggressive surgical management. There is a lower incidence of recurrence following resection of the focal, nodular form of GCTTS relative to the diffuse or florid type, which can have a recurrence rate of up to 50%.

Figure 5

As with many other soft-tissue masses, GCTTS can be difficult to see radiographically, especially when smaller in size. There is usually no associated osseous change, although there have been reported cases of associated osseous erosion. Even when a soft-tissue prominence or density is visible radio-graphically, its appearance is relatively nonspecific. MR imaging can be helpful diagnostically; the appearance of the focal form is generally decreased signal intensity on both T1-and T2-weighted MR imaging. As this is an uncommon appearance of soft-tissue masses that are extra-articular, this MR appearance may suggest the diagnosis of GCTTS.⁴

Conclusion

As seen in this case, GCTTS is a small, benign soft-tissue mass that commonly affects the hands and feet. Although conventional radiographic findings are non-specific, MR imaging can be effective in further characterizing these tumors.

References

1. Ushijma M, Hashimoto H, Tsuneyoshi M, et al. Giant cell tumor of the tendon sheath. Cancer. 1986;57:875-884.
2. Manaster BJ, Doyle AJ. Giant cell tumors of bone. Radiol Clin North Am. 1993;31:299-323.
3. 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;162:919-922.
4. Aoki J, Tanikawa H, Ishii K, et al. MR findings indicative of hemosiderin in giant-cell tumor of bone: Frequency, cause, and diagnostic significance. AJR Am J Roentgenol. 1996; 166:145-148.