Multiple Colorectal Adenomas Syndrome with Malignant Degeneration in Multiple Colorectal Polyps: 18F-Fluorodeoxyglucose Positron Emission Tomography-Computed Tomography Findings.

Multiple colorectal adenomas (MCRAs) syndrome is a genetic syndrome characterized by multiple colorectal polyps. Patients usually present late in late fourth or fifth decade of life. They have a high risk for developing malignancy. We here present such case of a 61-year-old man with MCRAs who developed malignant degeneration of multiple colorectal polyps, which was demonstrated on 18F-fluorodeoxyglucose positron emission tomography-computed tomography.

A 61-year-old male presented with 3 months history of episodes of bleeding per rectum. A colonoscopy was performed which revealed ulcerative lesion at anorectal junction. Also noted were multiple sessile and pedunculated polyps in the entire colon, but none were ulcerated or obstructive. A biopsy was performed from the anorectal lesion which showed Grade 2 adenocarcinoma. Biopsy from one other sigmoid colon polyp was negative for malignancy. Hence, a diagnosis of polyposis coli with anorectal adenocarcinoma was made. Serum carcinoembryonic antigen (CEA) level was 19.3 ng/ml (normal <5 ng/ml). A contrast enhanced 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) was performed for staging. Maximum intensity projection PET images revealed multiple 18F-FDG avid foci in the abdomen [Figure 1a, arrows]. PET-CT images reveal mildly enhancing 18F-FDG avid (maximum standardized uptake value [SUVmax]-10.3) circumferential wall thickening involving lower rectum and anorectal junction [Figure 1b and c, arrows], along with multiple 18F-FDG avid (SUVmax-4.2) mesorectal and pararectal nodes [Figure 1d and e, arrows]. Also, noted were multiple small and large 18F-FDG avid polyps in the colon [Figure 1f–i, arrows], largest in the descending colon [Figure 1i, SUVmax-6.5]. There were no distant metastases on PET-CT. The 18F-FDG avid colorectal polyps were reported as dysplastic with possible malignant transformation. A repeat colonoscopy was performed, and biopsy was performed specifically from the large hepatic flexure polyp and descending colon polyp mentioned in PET/CT report. Biopsy confirmed malignant transformation in both of them. The patient underwent total colectomy with nodal dissection and ileostomy, followed by adjuvant FOLFOX chemotherapy. The patient is doing fine at 6 months follow-up, with serum CEA of 2.1 ng/ml (normal <5 ng/ml).

Figure 1

Maximum intensity projection positron emission tomography images revealed multiple 18F-fluorodeoxyglucose avid foci in the abdomen (a, arrows). Positron emission tomography-computed tomography images reveal mildly enhancing 18F-fluorodeoxyglucose avid circumferential wall thickening involving lower rectum and anorectal junction (b and c, arrows), along with multiple 18F-fluorodeoxyglucose avid mesorectal and pararectal nodes (d and e, arrows). Also noted were multiple small and large 18F-fluorodeoxyglucose avid polyps in the colon (f-i, arrows), largest in the descending colon (i)

The presence of polyps is a risk factor for colorectal adenocarcinoma, and the risk is dependent on size, grade of dysplasia, and number of polyps.[12] Hence, conditions associated with multiple colorectal adenomas (MCRAs) are, therefore, the high risk for developing colorectal cancers. The most common polyposis disorders include familial adenomatous polyposis (FAP) and MCRAs syndromes.[34] In contrast to FAP who present at puberty and have positive family history, MCRAs patients usually present late in late fourth or fifth decade of life and might not have a family history, as in the present case.[5] The number of polyps is usually more than 10 but less than 100, while that in the case of FAP they are numerous (>100). Extra-colonic manifestations of FAP may be rarely present, though not seen in the present patient. Similar to FAP where it is always genetic associated with APC gene mutation, MCRA could be genetic but can be sporadic type well. Due to late presentation and lower risk of malignancy compared to FAP colon preserving surgery can be contemplated in MCRAs, while colectomy is the treatment of choice for FAP.[6] Unfortunately, in this patient, few other polyps also showed malignant degeneration and hence had to undergo total colectomy. The present case demonstrates the potential utility of 18F-FDG PET-CT for identifying malignant degeneration of polyps in patients with MCRAs[78] and thus accurately guiding the biopsy.

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