68Ga-FAPI-04 PET/CT Demonstrates Subtype-specific Uptake Patterns in Endometriosis With Added Diagnostic Value Beyond MRI

A 44-year-old woman with biopsy-proven endometriosis underwent 68 Ga-FAPI-04 PET/CT. MRI revealed bilateral ovarian endometriomas, uterine adenomyosis, and deep pelvic endometriotic lesions. FAPI PET/CT demonstrated concordant uptake in deep infiltrating lesions and intense uterine uptake corresponding to adenomyosis. Importantly, FAPI PET/CT detected an additional sigmoid-rectal junction lesion not visible on MRI, surgically confirmed as bowel endometriosis. Distinct subtype-specific uptake patterns were observed: highest in adenomyosis, high to moderate in deep infiltrating lesions, and mild peripheral uptake around ovarian endometriomas. This highlights FAPI PET/CT's complementary diagnostic value in endometriosis evaluation.