Medication Summary
The FDA approved pexidartinib as the first systemic therapy approved for tenosynovial giant cell tumor (TGCT) in 2019. Pexidartinib is a first-in-class inhibitor of colony stimulating factor-1 receptor (CSF1R), a tyrosine kinase receptor. Approval was based on the ENLIVEN study, which demonstrated a significant overall response rate with pexidartinib as compared with placebo (38% vs 0%; P < .0001). [39]
CSF1R Inhibitor
Class Summary
Inhibition of colony stimulating factor-1 receptor (CSF1R), a tyrosine kinase receptor, prevents interleukin-34 activation. Blocking IL-34 and the production of inflammatory mediators by macrophages and monocytes is thought to inhibit tumor cell proliferation.
Pexidartinib (Turalio)
CSF1R inhibitor. It is indicated for adults with tenosynovial giant cell tumor (TGCT) that is associated with severe morbidity or functional limitations and is not amenable to improvement with surgery. A lower dose was approved in October 2022 to reduce risk of adverse effects, including hepatotoxicity. Administer with a low-fat meal (~11-14 g total fat).
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Image in a 44-year-old right hand–dominant man who presented with a mass on the volar radial aspect of his left index finger. The mass was painless and had been slowly growing for 1.5 years.
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Radiograph demonstrates cortical erosion from the pressure effect of the adjacent mass on the radial aspect of the proximal phalanx.
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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.
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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.
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Radiograph demonstrates cortical erosion from the pressure effect of the overlying giant cell tumor of the tendon sheath.
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Histologic findings of a giant cell tumor of the tendon sheath.
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High-power photomicrograph depicts the histologic findings of a giant cell tumor of the tendon sheath.
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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.
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Typical T1-weighted MRI appearance of a giant cell tumor of the tendon sheath. Portions of the tumor have decreased signal intensity.
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Typical T1-weighted MRI findings in a giant cell tumor of the tendon sheath overlying the metacarpophalangeal joint. Note the low-signal-intensity areas.
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Corresponding T2-weighted MRI findings in the tumor shown in the image above. Note the areas of low signal intensity.
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Intraoperative excision of the giant cell tumor of the tendon sheath, which has the typical golden-yellow color secondary to hemosiderin deposition. The radial digital nerve is dissected free and slightly volar to the mass.
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After excision, the bone is curetted, leaving the exposed radial aspect of the proximal phalanx, as shown here.
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Giant cell tumor of the tendon sheath after marginal excision.
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Typical microscopic appearance of a giant cell tumor of the tendon sheath. Sheets of rounded or polygonal cells blend with hypocellular collagenized zones; variable numbers of giant cells are present.
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High-power photomicrograph of giant cell tumor of the tendon sheath shows occasional numerous mononuclear cells, scattered giant cells, and hemosiderin-containing xanthoma cells.
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An 11-year-old girl presented with this firm nonfluctuant mass over her posterior medial left ankle that had been present for 5 months and had not increased in size. The mass was not transilluminating. Findings on frozen section were consistent with a benign giant cell tumor of the tendon sheath. The mass was marginally excised.
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Giant cell tumor of the tendon sheath after marginal excision from an 11-year-old girl who presented with a firm nonfluctuant mass over her posterior medial left ankle that had been present for 5 months and had not increased in size.
