PMC9791217_01
The morphology of both the primary tumor (A) and the metastasis from the femoral head (B) show cellular sheets of small round to spindle cells merging with foci of cartilaginous differentiation (arrow). On immunohistochemistry, p16 expression is retained in the primary tumor (C) and lost in the metastasis (D).
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The biopsy showed a biphasic tumor consisting of solid sheets of small round to spindle cells admixed with islands of hyaline cartilage ( Figure 1 ).
FDG PET/CT [(A) 7/21] with multiple FDG avid bone metastases (ribs, spine, femurs, humerus, skullcap). SUV max, in the large left sided rib metastasis 13.7. FDG PET/CT [(B) 10/21] 10 weeks after start of TKI treatment with reduction of uptake in all bone metastases (rib lesion reduction to SUV max. 4.0). No new FDG avid lesions visible. FDG PET/CT [(C) 4/22] 9 months and [(D) 7/22] 12 months after TKI start with ongoing good response.
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Subsequently, the irradiated areas showed no FDG-uptake in the PET-CT anymore, but new and partly progressive osteolytic lesions on the left skullcap, spine, ribs, both femurs, and humerus were detected ( Figure 2A ). Additional FDG PET-CT scans carried out after 27, 37, 48, and 60 weeks confirmed a sustained partial response ( Figure 2 ).
Detailed timeline showcasing relevant data from the episode of care.
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A detailed timeline with relevant data from the episode of care is presented in  Figure 3 .