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Mentions: Two months after the FDG-PET scan, a colonoscopy was performed. There was no visible abnormality in the cecum (Figure 2) but prompted by the positive PET scan, a biopsy was obtained. During the biopsy, the gastroenterologist noted abnormal tissue consistency and suspected a blanket of polyps. Multiple biopsies were obtained although no gross abnormality was visible. The pathology results showed a villotubular adenoma without high grade dysplasia. An exploratory laparatomy was performed one month after the colonoscopy to remove the tissue with abnormal histology. Gross pathology showed an exophytic polypoid lesion in the cecal pouch, adjacent to the ileocecal valve. The lesion measured 4.5 × 3 × 0.5 cm. Microscopic examination revealed villous adenoma with focal high grade dysplasia, negative for invasive carcinoma (Figure 3). Surgical margins and lymph nodes were free from dysplasia. A subsequent whole-body FDG PET/CT scan performed 10 months postoperatively was found to be normal.
Advanced adenoma diagnosis with FDG PET in a visibly normal mucosa: a case report
Bottom Line: A focal cecal uptake with a standardized uptake value (SUV) of 8.9 was found on the PET scan.Pathology from tissue extracted during an exploratory laparatomy completed one month later found the lesion to be a villous adenoma with high grade dysplasia.A positive FDG PET scan indicative of colorectal cancer should be followed up with a colonoscopy and biopsy even in a visibly normal mucosa.
Affiliation: Dept, of Nuclear Medicine/PET, Kettering Medical Center, Southern Blvd, Kettering, OH 45429, USA. email@example.com.
Background: An accurate, early diagnosis and treatment of adenomatous polyp can curtail progression to colorectal cancer. F-18 fluorodeoxyglucose positron emission tomography (F-18 FDG PET) reveals the biochemical changes associated with the development of many cancers which precede the appearance of gross anatomical changes that may be visualized during surgical resection or via imaging with MR or CT.
Intervention: We detail the history of a 64 year old female who had a whole-body FDG PET scan as a part of an employee wellness program. A dose of 12.2 mCi of F-18 labeled FDG was administered.
Results: A focal cecal uptake with a standardized uptake value (SUV) of 8.9 was found on the PET scan. Conversely, only normal mucosa was observed during a colonoscopy done 2 months after the PET scan. Motivated by the PET scan finding, the colonoscopist performed a biopsy which revealed a villous adenoma without high grade dysplasia. Pathology from tissue extracted during an exploratory laparatomy completed one month later found the lesion to be a villous adenoma with high grade dysplasia.
Conclusion: Whole-body FDG PET scan revealed the biochemical metabolic changes in malignancy that preceded the appearance of any gross anatomical abnormality. A positive FDG PET scan indicative of colorectal cancer should be followed up with a colonoscopy and biopsy even in a visibly normal mucosa.