Figure 1.

CT scan of the right foot showing an osteolytic lesion of the calcaneus with extensive cortical destruction, with some areas with mild sclerotic reaction and permeative pattern in the anterior aspect. Soft tissue involvement and inhomogeneous contrast enhancement (CE), as well as invasion of the cuboid. Avid FDG uptake was present at PET/CT, with 11.6 Standarized Uptake Value (SUV) (A). Two months after neoadjuvant chemotherapy, an increase in overall size of the lesion was observed at CT scan, associated with increased necrotic component, presenting with more peripheral CE; FDG uptake at PET/CT was still avid (B). Two months after larotrectinib therapy, lesion response showed a significant decrease in size, with reduction of the soft tissue component of the mass, mild and inhomogeneous restoration of cortical margins with increased perilesional sclerotic aspects, and significant decrease in FGD uptake (SUV max 3) (C).