Incidental second primary in the breast detected by F-18 FDG positron emission tomography scan

A 39-year-old women had multiple lung lesions on a follow-up chest radiograph after laparotomy and left cystectomy for an immature ovarian teratoma. Results of a work-up for metastases were normal, including beta human chorionic gonadotrophin and alpha-fetoprotein levels. An F-18 FDG positron emission tomographic (PET) whole-body scan performed to evaluate the possibility of pulmonary metastases showed no abnormality in the chest or pelvis. There was intense focal uptake in the left breast, however, suggesting an incidental second malignancy. Pathologic evaluation of the left breast mass showed infiltrating ductal cell carcinoma, for which she received chemotherapy. Histologic examination of the lung lesions showed a benign mature teratoma in one nodule and fibrosis in several of the others. In a patient with a neoplasm, F-18 FDG uptake on a whole-body scan may be unrelated to the primary tumor and could represent an incidental second malignancy.