Combination of 68Ga-FAPI-04 and Dedicated Breast PET (MAMMI PET) Outperformed Breast MRI and 18F-FDG PET/CT by Revealing Nipple and Skin Involvement of Breast Cancer.

A 41-year-old woman with newly diagnosed breast cancer had suspicious clinical findings of skin involvement on physical examination. The primary tumor had no FDG uptake in 18F-FDG PET/CT. Nipple and skin had no pathologic enhancement for invasion in breast MRI. Because the T stage was unclear, the patient underwent 68Ga-FAPI-04 PET/CT for further evaluation. Combination of 68Ga-FAPI-04 with dedicated breast PET (MAMMI PET) showed nipple and skin involvement of breast cancer with intense FAPI uptake. Consequently, a skin-sparing mastectomy was performed. Histopathological examination confirmed invasive lobular carcinoma infiltration of the deep dermis in the nipple and skin tissue.