Metachronous Ectopic CRH-Secreting Tumors Detected by 68Ga-Pentixafor PET/CT

A 39-year-old woman with ACTH-dependent Cushing syndrome underwent pituitary surgery after bilateral inferior petrosal sinus sampling (BIPSS) suggested a central source; however, symptoms persisted, and pathology revealed an ACTH-negative adenoma, raising suspicion for ectopic corticotropin-releasing hormone (CRH) secretion. Subsequent ⁶⁸ Ga-DOTATATE PET/CT was negative. CXCR4-targeted ⁶⁸ Ga-Pentixafor PET/CT demonstrated focal intense uptake in a right neck lesion, confirmed as a CRH-secreting tumor by histopathology. Two years later, recurrence revealed a second anatomically distinct lesion in the right thigh, also histologically confirmed. This case highlights the value of ⁶⁸ Ga-Pentixafor PET/CT in detecting metachronous ectopic CRH-secreting tumors.