False positive F-18 fluorodeoxyglucose combined PET/CT scans from suture granuloma and chronic inflammation: report of two cases and review of literature.
BACKGROUND
F-18 fluorodeoxyglucose (FDG) combined positron emission tomography (PET)/ computed tomography (CT) imaging is often used in the surveillance of recurrent colorectal cancers after curative resections. We report 2 patients where FDG combined PET/CT imaging produced false positive results due to chronic inflammation and suture granuloma.


METHODS
Case 1 is a patient with a curative anterior resection done 10 months ago. Serial surveillance carcinoembryonic antigen (CEA) showed a marginal elevation. A solitary "hot spot" on combined PET/CT imaging was seen at the level of the previously resected inferior mesenteric vein. Case 2 is a patient with a positive solitary lesion on combined PET/CT imaging 16 months after a curative right hemicolectomy for colorectal cancer. The serum CEA was within normal limits.


METHODS
Both patients had undergone exploratory laparotomy with complete resection of the solitary lesions.


RESULTS
The histology of Case 1 was reported as a suture granuloma while the histology of Case 2 was reported as an inflammatory nodule related to the previous suture pedicle, both with no malignant tissues identified.


CONCLUSIONS
False positives on combined PET/CT imaging may result from inflammatory granulomas months after surgery.
Lim
J W M
JW
Faculty of Medicine, National University of Singapore, Singapore.
Tang
C L
CL
Keng
G H W
GH
D000328:Adult; D002908:Chronic Disease; D003937:Diagnosis, Differential; D005189:False Positive Reactions; D005260:Female; D019788:Fluorodeoxyglucose F18; D005500:Follow-Up Studies; D006099:Granuloma / Q000175:diagnosis / Q000000981:diagnostic imaging*; D006801:Humans; D007249:Inflammation / Q000175:diagnosis / Q000000981:diagnostic imaging*; D007813:Laparotomy; D008875:Middle Aged; D009367:Neoplasm Staging; D049268:Positron-Emission Tomography; D018570:Risk Assessment; D012811:Sigmoid Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery; D013537:Sutures; D014057:Tomography, X-Ray Computed
D019788:Fluorodeoxyglucose F18