Incidental Positron Emission Tomographic (PET) Demonstration of Abnormal Focal 18-FDG (Fluoro-Deoxy-Glucose) Uptake within the Colon May Be Related to Benign, Precancerous, or Malignant Tumors

Abstract

Purpose: Incidental positron emission tomographic (PET) demonstration of abnormal focal 18-FDG (fluoro-deoxy-glucose) uptake within the colon may be related to benign, precancerous, or malignant tumors. We report a case of an incidental hyperplastic polyp of the colon discovered due to increased uptake on PET scan during breast cancer evaluation. Case Report: A 56-year-old woman with recently diagnosed breast cancer underwent an 18-FDG PET scan to further evaluate bilateral pulmonary nodules and two low attenuated liver masses detected on CT scan. The PET study showed no abnormal radiotracer uptake in either lung, essentially ruling out the possibility of lung metastasis from the breast carcinoma. There was, however, a focus of localized radiotracer accumulation within the proximal ascending colon (SUV of 8.38) and the liver (SUV of 4.7). Colonoscopy revealed a polyp in the area of increased uptake as well as two additional polyps in the cecum and transverse colon. These were hyperplastic polyps on pathological examination. A percutaneous biopsy of the liver mass contained a hemangioma. Discussion: During initial or staging work up an unexpected abnormal focal uptake may be noted on 18-FDG PET scans. This patient population may also be at a high risk for primary colon cancer and further workup may be necessary to evaluate PET findings. Premalignant colonic lesions such as villous and tubulovillous adenomas have been reported with increased uptake on PET scans. Their detection is related to their size (>1.3 cm) and preferential locations at the less mobile segments of the colon. Recently, hyperplastic polyps, usually considered as benign and nonneoplastic lesions of the colon, have been reported as additional causes of focal colonic 18-FDG uptake. Contrary to the diffuse pattern of FDG accumulation in the colon, which is mostly benign and physiologic, focal radiotracer colonic uptake on. In a study of 197 patients with lung cancer, 59 had diffuse colonic uptake and 17 had focal colonic uptake on PET scans. Of those, 5 were found to be malignant on biopsy. Conclusions: Colonoscopy with biopsy may be recommended for evaluation of patients with localized colonic uptake on PET scans. Diffuse FDG uptake is usually associated with normal colonoscopy and may not need a colonoscopic evaluation in all patients.