Nuclear Medicine Imaging in Tumor Diagnostics Using FAPI-PET/CT: A Case-based Perspective on Malignant Peripheral Nerve Sheath Tumor.

Unlike FDG, FAPI tracers target fibroblast activation protein inhibitor (FAPI), highly expressed in the tumor microenvironment. This allows better differentiation between viable tumor and post-therapeutic changes, that is, fibrosis or inflammation. Here, a 39-year-old man with a malignant peripheral nerve sheath tumor (MPNST) of the thoracic wall underwent surgery and adjuvant radiotherapy. FAPI-PET/CT 3 months after treatment showed paravertebral and diffuse pleural uptake. Biopsy verified tumor recurrence and pleural sarcomatosis. Among others, a FAPI-radioligand-therapy was initiated. This case demonstrates the efficacy of FAPI imaging in the staging and potential treatment of MPNST and pleural sarcomatosis.