• Benign, well circumscribed proliferation of mononuclear cells admixed with variable proportions of osteoclast-like giant cells, foamy histiocytes, siderophages and inflammatory cells

• X-ray: (Radiol Med 2010;115:141)
  • Most commonly demonstrate a soft tissue mass, some of which demonstrates bony erosion
• Ultrasonography: (Radiol Med 2010;115:141)
  • Lesion does not move with the tendon during flexion / extension
  • Solid, not cystic (helps to differentiate from ganglion cyst)
• MRI findings: (Oncol Lett 2017;13:4459)
  • Well demarcated
  • Associated with a tendon (and encasing a tendon in some instances)
  • May have variability in signal intensity but will, in general, have foci of low intensity on T1WI and T2WI from hemosiderin

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The image above comes from a finger mass of a 45 year old woman. Grossly, the lesion was well circumscribed and bosselated. Which of the following features must be identified to the make the diagnosis?


1. Foamy macrophages
2. Hemosiderin laden macrophages
3. Histiocytoid mononuclear cells
4. Inflammatory cells
5. Multinucleated giant cells

C. Histiocytoid mononuclear cells. The pictured lesion is a tenosynovial giant cell tumor, localized type (also called giant cell tumor of tendon sheath). Although all the listed cell types can be seen in varying proportions within the tumor, the histiocytoid mononuclear cells are the neoplastic component and should always be present.

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Reference: Tenosynovial giant cell tumor, localized type

Which of the following is true about a tenosynovial giant cell tumor, localized type?


1. Both genders are affected equally
2. The diagnosis can be made even in the absence of osteoclast-like giant cells
3. Highly infiltrative lesion, which lead the majority to recur
4. It is the most common tumor of the hand
5. The patient always reports a history of trauma

B. The diagnosis can be made even in the absence of osteoclast-like giant cells. Some cases show a paucity of giant cells, which is why it is best to know the constellation of histologic features aside from the presence of giant cells in order to make the diagnosis in giant cell poor cases. Tenosynovial giant cell tumor, localized type, is the second most common tumor of the hand (ganglion cyst is most common). It shows a predilection for females (F:M=2:1). The tumors are usually well circumscribed. They may recur but simple excision is curative the majority of the time. Some patients report a history of trauma but not all.

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Reference: Tenosynovial giant cell tumor, localized type