From One Cancer to Two: [¹⁸F]FES PET/CT Redirected Diagnosis and Therapy in a Metastatic Breast Cancer Patient.

Dupont, Anne-Claire; Farges, Mathieu; Chapelle, Benoit; Cancel, Mathilde; Ribeiro, Maria-Joao Santiago · Clin Nucl Med · 2026

case_report · Level V

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Abstract

A 59-year-old woman with an ulcerated right breast lesion was diagnosed with ER-positive invasive ductal carcinoma. Staging [¹⁸F]FDG PET/CT revealed intense uptake in the breast, axillary nodes, a large hypermetabolic pulmonary mass, mediastinal lymphadenopathies, and bone lesions. Because of this metabolic pattern, [¹⁸F]FES PET/CT was performed, demonstrating [¹⁸F]FES-avid bone metastases but no uptake in the lung mass. Biopsy confirmed a BRAF V600E-mutated lung adenocarcinoma. [¹⁸F]FES PET/CT proved crucial in differentiating synchronous primary malignancies from metastatic spread and guiding targeted therapy with dabrafenib-trametinib.

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