PMC9741540_01
Representative MRI slices from of a 29-year-old male with D-TGCT in the left hip at diagnosis. Coronal (a, b) and axial (c) MR imaging demonstrating severe arthritic changes of the left hip joint with erosions present (*), (b) massive TGCT tumor burden running along the anterior hip and into the pelvis adjacent to the iliacus muscle (arrowhead), and (c) tumor burden both posterior to the hip in the ischiofemoral fossa and anterior to the psoas insertion (arrow).
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After an unsuccessful trial of physical therapy, an MRI was obtained in December 2019 that showed a lobulated mass anteriorly and posteriorly around the left hip extending into the left pelvis anteromedial to the iliacus musculature and posteriorly into the ischiofemoral space (Figures 1(a)-1(c)). A representative measurement performed at the level of the external iliac vessels measured 7 cm x 3 cm x 7 cm. There was advanced left hip arthritis with severe joint space narrowing, subchondral sclerosis, cartilage loss, and osteophytic spurring (Figures 1(a)-1(c)).
Histology images in the hip prior to pexidartinib treatment. The pretreatment biopsy demonstrating a cellular proliferation of tumor cells composed of abundant hemosiderin laden macrophages, multinucleated giant cells, scattered foam histiocytes, and lymphocytes (H&E 200X).
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Sections of the tumor from the pretreatment biopsy demonstrated a cellular lesion composed of mixed inflammatory cells including macrophages with hemosiderin pigment and abundant multinucleated giant cells, as well as collections of foamy histiocytes and lymphocytes (Figure 2).
Representative MRI slices of a 29-year-old male with D-TGCT in the hip 12 months after the initiation of pexidartinib. Post-pexidartinib treatment coronal (a, b) and axial (c) MR imaging demonstrates persistent end stage hip arthritis (*) but significant reduction in TGCT tumor burden tracking along the anterior hip into the pelvis (arrowhead) as well as significant reduction of both the ischiofemoral and anterior psoas tumor burden (arrow).
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At a follow-up visit in December 2020, MRI revealed a reduction in tumor size, with representative tumor measurements performed at the level of the external iliac vessels of 5.0 cm x 2.1 cm and at the ischiofemoral space of 4.3 cm x 2.0 cm (Figures 3(a)-3(c)), specifically involving the iliopsoas bursa and ischiofemoral space.
Histology images in the hip post-pexidartinib treatment. The posttreatment specimen was less cellular compared to the pretreatment tissue and demonstrated a relative increased number of foamy histiocytes and significantly decreased number of multinucleated giant cells (H&E 200X).
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However, compared to the pretreatment sample, the tissue was less cellular, the foamy histiocytic component was increased, and the number of multinucleated giant cells were significantly decreased (Figure 4).
Representative MRI slices and postoperative radiographs of a 29-year-old male with D-TGCT in the left hip. Coronal MRI with metal subtraction (a, b) demonstrates near resolution of the intrapelvic tumor burden (arrowhead). Axial imaging (c) demonstrates absence of posterior tumor burden after surgical resection (arrow) but persistence of the small anterior tumor along the psoas muscle (*). A well-fixed cementless total hip arthroplasty is demonstrated (d).
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Follow-up X-rays demonstrated a well-sized and fixed cementless total hip arthroplasty (Figures 5(a)-5(d)). Surveillance MRI at the same time demonstrated resection of the tumor from the ischiofemoral space with slight shrinkage of the anterior tumor along the iliac vessels (now 4.3 cm x 1.1 cm) (Figures 5(a)-5(d)).
PMC9741540_02
Representative images of a 35-year-old female with D-TGCT in the foot. Large erosion at the medial head of the first metatarsal, and throughout the midfoot, consistent with reported history of D-TGCT from an (a) oblique (arrow), (b) anterior-posterior (arrow), and (c) lateral view with multiple sites of midfoot erosions.
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Four months later at a follow-up visit in July 2019, an ill-defined soft tissue mass with associated erosions in the midfoot measuring 3.0 cm x 2.0 cm x 2.8 cm was observed in the radiographs (Figures 6(a)-6(c)).
Sagittal and axial images of a 35-year-old female with D-TGCT in the foot. Soft tissue masses at the medial margin of the first metatarsal head and centered about the first through fourth tarsometatarsal joints and extending to the navicular bone appear unchanged, with accompanying bony erosions. These demonstrate low signal on T1 images, compatible with provided history of diffuse tenosynovial giant cell tumor. Low-signal mass dorsal to the fourth tarsometatarsal joint: (a, b) T1 weighted sagittal images of the foot (arrow) and (c) T1 weighted axial view of the foot (arrow).
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The mass measured 3.0 cm in the anterior-posterior dimension and 2.0 cm x 2.8 cm in transverse dimension (Figures 7(a)-7(c)).
Coronal and sagittal images of a 35-year-old female with D-TGCT in the foot. (a) Coronal and (b) sagittal T1 weighted images demonstrating overall stable appearance of the hypointense T1 weighted images of the foot (arrow), consistent with known D-TGCT.
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In March 2020 at a follow-up visit, an MRI (Figures 8(a) and 8(b)) showed decreased enhancement and volume of TCGT soft tissue lesions at the midfoot and decreased marrow enhancement at the first metatarsal head.
Sagittal and axial images of a 35-year-old female with D-TGCT in the foot. Sagittal T1 weighted images (a, b) (arrow) and axial T1 weighed image (c) (arrow) demostrating stable involvement of the forefoot and midfoot with known history of D-TGCT on serial imaging.
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PMC9741540_03
Axial and sagittal images of a 55-year-old male with D-TGCT in the knee. (a) MRI with axial T2 fat suppressed images of the proximal lower leg. The large posteromedial hyperintense mass (star) shows a fluid-fluid level from the synovial fluid in the anterior aspect and proteinaceous and bloody fluid posteriorly. (b) MRI sagittal T1 view of the knee. Anteriorly, (star) the suprapatellar pouch is filled with an intermediate intensity fluid and contains diffuse hypointense material characteristic for the solid component of tenosynovial giant cell tumor. Posterior to the joint, there are multiple aggregations of hypointense masses along the posterior capsule and origins of the gastrocnemius muscles and the posterior cruciate ligament. Posteriorly, (arrow) the enormous popliteal cyst is evident with intermediate intensity. (c) MRI with sagittal T2 fat suppressed images of the knee. This shows the same fluid filled suprapatellar pouch with diffuse areas of lower intensity scattered throughout (star). Diffuse dark bands of thickened posterior capsule and tumor extend outside the joint and behind the posterior cruciate ligament (plus). The large hyperintense fluid filled popliteal cyst with scattered hypointense bands and nodules are present posteriorly (arrow).
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Three weeks later, a left knee arthroscopy with total synovectomy confirmed D-TGCT (Figures 10(a)-10(c)).
Histology images in the knee post-pexidartinib treatment. Hypercellular region of the popliteal tumor after pexidartinib treatment is indistinguishable from that seen in the original biopsy (a). This photomicrograph displays areas of highly mitotic proliferative tumor (19 mitoses per 10 high power fields) that were widely seen in the viable tumor (b). Approximately, 30% of the mass was composed of these areas of fibrotic hypocellular tissue with low proliferative rates (c).
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Sections from the histological examination of the resection specimen show that the hypercellular region of the popliteal tumor (Figure 11(a)) is similar to what was observed prior to pexidartinib treatment. In addition, areas of highly mitotic proliferative tumor were present (Figure 11(b)), and nearly one-third of the tumor was made up of fibrotic, hypocellular tissue with low proliferative rates (Figure 11(c)).
Axial, coronal, and sagittal images of a 55-year-old male with D-TGCT in the knee. MRI shows tumor measuring 2.8 cm x 1.4 cm was in the medial and lateral gutters (star) along with tumor in the intercondylar notch posteriorly (plus). There were also synovial thickened nodules extending into the popliteal cyst, which shrank to 5.8 cm and contained hypointense debris and hemorrhage (arrow). (a) An axial fat suppressed image of the distal femur, (b) a coronal T2 fat suppressed image of the knee, and (c) a sagittal T2 fat suppressed image of the lateral aspect of the knee joint that best demonstrated the residual tenosynovial giant cell tumor (arrow).
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In October 2020, MRIs showed lesions measured at 2.8 cm x 1.4 cm in the medial gutter and posterior intercondylar notch (Figures 12(a)-12(c)).
Effusion in the knee of a 55-year-old male with D-TGCT. No tumor recurrence is observed following rupture of anterior cruciate ligament. (a) This axial view with contrast of the distal femur shows a suprapatellar pouch effusion with hyperintense capsular enhancement (plus). No tumor is visible. (b) The axial view at the level of the menisci has areas of hypointensity interpreted by the radiologist as scar rather than tenosynovial giant cell tumor along the posterior cruciate ligament insertion (star). (c) This sagittal view shows a dramatic reduction of the popliteal cyst with small residual nodules of debris in the cyst (arrow).
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A new rupture of the anterior cruciate ligament and thinning of the posterior cruciate ligament were observed; there was no evidence for recurrent TGCT (Figures 13(a)-13(c)).