Soft tissue

• Tenosynovial giant cell tumor encompasses a group of lesions that most often arise from the synovium of joints, bursae and tendon sheaths and show synovial differentiation
• Malignant tenosynovial giant cell tumor is very uncommon and is defined by the coexistence of a benign tenosynovial giant cell tumor with overtly malignant areas or by recurrence of a typical giant cell tumor as a sarcoma

• Acceptable: giant cell tumor of tendon sheath
• Not recommended: pigmented villonodular synovitis

• Translocation of the CSF gene that encodes colony stimulating factor 1 (CSF1) was frequently involved in this tumor
• It is reported that tumor cells with CSF1 translocation synthesize large amounts of the CSF1 protein
• Actually, only a small subset of cells harbor the translocation

• Unknown

Contributed by Jigang Wang, M.D., Ph.D. and Jiufa Cui, M.D., Ph.D.

Diffuse type



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Contributed by Mark R. Wick, M.D.

Localized type


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Contributed by Mark R. Wick, M.D.


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• Composed of mononuclear cells, multinucleated giant cells, foamy macrophages, inflammatory cells and hemosiderin
• 2 principal cell types of the mononuclear components:
  • Small histiocyte-like cells: pale cytoplasm and round or reniform nuclei
  • Large epithelioid cells: amphophilic cytoplasm and rounded vesicular nuclei, often containing a peripheral rim of hemosiderin granules
• Mitotic activity may be brisk
• Necrosis can be present
• Localized type (J Surg Oncol 1998;68:100)
  • Lobulated and well circumscribed
  • Osteoclast-like giant cells are usually readily apparent
  • Xanthoma cells are frequent, tend to aggregate locally near the periphery of nodules, and may be associated with cholesterol clefts
  • Hemosiderin deposits
  • Stroma showed variable degrees of hyalinization
• Diffuse type (J Surg Oncol 1998;68:100, J Oral Maxillofac Surg 2019;77:1022.e1)
  • Infiltrative, and grow as diffuse, expansile sheets
  • Osteoclast-like giant cells are less common in the diffuse form than the localized form and may be absent or extremely rare in as many as 20% of cases
  • Cleft-like spaces are common and appear either as artifactual tears or as synovial lined spaces
  • Stromal hyalinization is common and may mimic osteoid
  • Blood filled pseudoalveolar spaces are seen in approximately 10% of cases
• Malignant (Hum Pathol 2017;63:144, Am J Surg Pathol 1997;21:153)
  • Composed of sheets and nodules of enlarged mononuclear cells
  • Significantly increased mitotic count, including atypical mitoses, necrosis, enlarged nuclei with nucleoli, spindling of mononucleated cells and myxoid changes
  • May contain areas that resemble undifferentiated pleomorphic sarcoma or myxofibrosarcoma

Contributed by Jigang Wang, M.D., Ph.D., Jiufa Cui, M.D., Ph.D. and Michella Whisman, M.D.

Localized type



Diffuse type

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Which of the following features must be identified to the make the diagnosis of tenosynovial giant cell tumor?

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

A. Epithelioid mononuclear cells. The 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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Which of the following is true regarding tenosynovial giant cell tumor, localized type?

1. Both genders are affected equally
2. Diagnosis can be made even in the absence of osteoclast-like giant cells
3. Highly infiltrative lesion, which leads to recurrence in the majority of cases
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 most of the time. Some patients report a history of trauma but not all.

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Which of the following is true regarding the location of diffuse tenosynovial giant cell tumor?

1. Knee is the most frequent, followed by hip and ankle
2. Often in foot and hand
3. Often occurs in small joint
4. Only intra-articular

A. Knee is the most frequent, followed by hip and ankle. Diffuse tenosynovial giant cell tumor often involves large joint and can be extra-articular. Localized tenosynovial giant cell tumor often occurs in small joint, such as foot and hand.

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A 15 year old girl presented with finger mass for 1 year. The tumor (shown above) was well defined, attached to the tendon and was approximately 1 cm in diameter. What is your diagnosis?

1. Chondroblastoma
2. Dermatofibroma
3. Fibroma of tendon sheath
4. Giant cell tumor
5. Tenosynovial giant cell tumor

E. Tenosynovial giant cell tumor. The pictured lesion is a tenosynovial giant cell tumor, localized type (also called giant cell tumor of tendon sheath). The tumor usually occurs in small joint and is attached to tendon sheath. Microscopically, the tumor was a giant cell rich tumor with prominent epithelioid mononuclear cells that can be observed.

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Which of the following is true regarding malignant tenosynovial giant cell tumor?

1. Malignant tumor from the location around large joint
2. May have a previous history or typical morphological area of tenosynovial giant cell tumor
3. Often occurs in upper extremities
4. Usually affects young people

B. May have a previous history or typical morphological area of tenosynovial giant cell tumor

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