Giant Cell Tumor of the Tendon Sheath Workup

• Plain radiography

  • Plain radiographs demonstrate a benign-appearing circumscribed soft-tissue shadow in 50% of cases. These radiographs also show cortical erosion of the bone due to a pressure effect of the adjacent mass on the cortex in 10-20% of cases (see the images below). Radiograph demonstrates cortical erosion from the pressure effect of the adjacent mass on the radial aspect of the proximal phalanx. Radiograph demonstrates the bony erosion associated with some giant cell tumors of the tendon sheath and shows the unmineralized soft-tissue shadow of the mass.
  • True bone invasion is not typical and is suggestive of an aggressive neoplasm.
  • Cortical erosion from these tumors is more common in the feet than elsewhere because the strong ligaments in this region frequently prevent outward tumor growth.
  • Occasionally, intralesional soft-tissue calcification is seen with giant cell tumors of the tendon sheath. This intralesional calcification can be confused with synovial chondromatosis, periosteal chondroma, or calcific tendinitis.
  • On rare occasions when extensive cortical erosion is present, the lesion may have a radiographic appearance suggestive of a periosteal chondroma (see the images below). Radiograph demonstrates cortical erosion from the pressure effect of the overlying giant cell tumor of the tendon sheath. This apple-core effect is indicative of a primary soft-tissue mass that is causing external erosion, which should not be confused with a primary bone process such as periosteal chondroma. Radiograph demonstrates cortical erosion from the pressure effect of the overlying giant cell tumor of the tendon sheath. Histologic findings of a giant cell tumor of the tendon sheath. High-power photomicrograph depicts the histologic findings of a giant cell tumor of the tendon sheath.
• Magnetic resonance imaging (MRI)

  • Giant cell tumors of the tendon sheath frequently have a unique MRI appearance for an extra-articular soft-tissue mass.^{[23, 24]} On both T1- and T2-weighted MRIs, at least some portions of the tumor have decreased signal intensity (see the images below) similar to that seen with PVNS. However, this appearance is not entirely specific to giant cell tumors of the tendon sheath. Typical T2-weighted MRI appearance of a giant cell tumor of the tendon sheath. Most of the tumor has intermediate signal intensity, and portions of the tumor have low signal intensity; the latter finding likely reflects signal attenuation due to hemosiderin deposition. Typical T1-weighted MRI appearance of a giant cell tumor of the tendon sheath. Portions of the tumor have decreased signal intensity. Typical T1-weighted MRI findings in a giant cell tumor of the tendon sheath overlying the metacarpophalangeal joint. Note the low-signal-intensity areas. Corresponding T2-weighted MRI findings in the tumor shown in the image above. Note the areas of low signal intensity.
  • The degree to which these low–signal-intensity areas are present depends on the amount of hemosiderin, which varies. PVNS often has more low–signal-intensity areas on T2-weighted images, secondary to its higher hemosiderin content resulting from characteristic intralesional bleeding.
• Sonography: For the value of sonograms, see studies by Bancroft et al^[24] and Wang et al^[25]

Gross pathologic findings

Giant cell tumors of the tendon sheath have a well-circumscribed multilobular appearance and often possess shallow grooves along their deep surfaces created by the underlying tendons. These tumors are usually small, with a diameter of 0.5-5 cm. Compared with other lesions, giant cell tumors in the hand digits are usually smaller and have a more regular appearance. Giant cell tumors in the feet and elsewhere are often larger and more irregular in appearance. On cut sections, these tumors have a mottled appearance, varying in color from grayish-brown to yellow-orange. The coloration depends on the amount of hemosiderin, collagen, and histiocytes in the sample. Tumors with more hemosiderin deposition due to bleeding have more of the yellow-orange or even reddish-brown color (see the images below).

Microscopic findings

Most giant cell tumors of the tendon sheath are moderately cellular and composed of sheets of rounded or polygonal cells that blend with hypocellular collagenized zones. Variable numbers of giant cells are present (see the first image below). Hemosiderin-containing xanthoma cells are common and often localized at the periphery of the lesion (see the second image below).

In the localized form of the disease, a mature collagen capsule often surrounds the tumor. This capsule is continuous, with fibrous septa within the substance of the tumor that divide it into vague nodules. In the diffuse form, the tumor is not surrounded by this capsule and instead grows in expansive sheets.

Giant cells are also less common in the diffuse form. The histologic features of the localized and diffuse forms of giant cell tumor of the tendon sheath and the localized and diffuse forms of PVNS are essentially the same; therefore, these diseases form a histopathologic spectrum in which the tumors range from benign lesions to more locally aggressive lesions.

Cytopathologic findings

The predominant cell type is the mononuclear cell. These round-to-polygonal cells are found alone or in papillary clusters and have eccentrically located nuclei that lack pleomorphism. Varying amounts of refractile golden-brown crystals of hemosiderin are characteristically found within the histiocytes.^{[26, 27]}