An FDG-PET/CT-Positive Lesion Mimicking Local Recurrence of Colon Cancer 5 Years after Radical Colectomy

Patient: Female, 75 Final Diagnosis: False positive findings Symptoms: — Medication: — Clinical Procedure: — Specialty: Surgery OBJECTIVE: Mistake in diagnosis BACKGROUND: Radical resection of colorectal cancer yields satisfactory results. Even if the cancer recurs, long-term survival is expected through further surgical resection of the recurrent disease. For early detection of recurrent lesions, we routinely perform periodic blood tests and imaging studies, in which (18)F-fluorodeoxyglucose-glucose positron emission tomography (FDG-PET) plays an important role, for lesion differentiation. We encountered a case of a benign lesion, which had been clinically diagnosed as recurrence of resected colon cancer by FDG-PET/computed tomography (CT). CASE REPORT: A 69-year-old woman underwent radical resection of stage II sigmoid colon cancer. Five years after the operation, local recurrence was suspected on the basis of follow-up CT examination findings. Since the standardized uptake value (SUV) on FDG-PET/CT was 13.3, we diagnosed the lesion as a postoperative local recurrence and performed surgical resection of the lesion. The lesion was conclusively diagnosed as benign fatty tissue, including a fibrovascular component, by histopathological examination. CONCLUSIONS: FDG-PET is a very useful technique for differentiating benign from malignant disease. In colorectal cancer, FDGPET not only enables the differentiation of malignancy in the primary tumor, but also the confirmation of metastasis and postoperative recurrence. However, even if the SUV is high, as in the presented case, the lesion may eventually be diagnosed as benign. Therefore, further advances in the PET technique are expected along with the development of more useful modalities.