[Malignant tumor with false negative 18F-FDG PET image].
OBJECTIVE
To investigate the FDG uptake characteristics, the factors affecting 18F-FDG uptake and the extra CT diagnostic value of 18F-FDG PET/CT scan in the malignant tumor with false negative 18F-FDG PET image.


METHODS
The data of PET/CT image in 17 patients with various kinds of cancers were reviewed and analyzed by visual observation and semi-quantity analysis ( SUV). The results were compared with the CT and histopathological diagnosis, respectively.


RESULTS
Of 6 well-differentiated HCC patients confirmed by histopathological diagnosis, one had two lesions in the right lobe of the liver. One of these two lesions showed low FDG uptake on 18F-FDG PET scan and low density on CT scan. The other one was not shown on either 18F-FDG PET or plain CT scan. But on enhanced CT scan, these two lesions were found to be inhomogeneous with high density at arterial phase. The false negative 18F-FDG PET images of one gastric signet ring cell carcinoma in the gastric fundus with right adnexa metastasis, 3 renal cell carcinoma, one greater omentum and peritoneal metastatic adenocarcinoma and one well-differentiated prostate cancer were caused by normal physical uptake in the digestive tract or FDG retention in the urinary system due to normal excretion. The size of three metastases was smaller than or equal to 1 cm in diameter, however, two primary lesions of these metastases showed high FDG uptake and only one was negative on either 18F-FDG PET or CT scan. In this series, 68.8% of the primary tumors and 66.7% of metastases were found to show abnormal density on CT scan, and 31. 2% of the primary tumors and 33. 3% of metastases were not detectable on either PET or CT images.


CONCLUSIONS
False negative 18F-FDG PET in malignant tumor may be correlated with the pathologic type, differentiation degree and the lesion size. Combining CT information with PET or paying attention to the scan methods during 8 F-FDG PET examination may reduce the rate of false negative 18F-FDG PET diagnosis in various kinds of malignant tumors.
Dong
Meng-jie
MJ
PET Canter Department of Nuclear Medicine, Huashan Hospital, Fudan University, Shanghai 200040, China.
Lin
Xinag-tong
XT
Zhao
Jun
J
Guan
Yi-hui
YH
Zuo
Chuan-tao
CT
Chen
Xiang
X
Dai
Jia-zhong
JZ
Jiang
Bao-dong
BD
D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000556:secondary; D000328:Adult; D000368:Aged; D006528:Carcinoma, Hepatocellular / Q000000981:diagnostic imaging* / Q000473:pathology; D002292:Carcinoma, Renal Cell / Q000000981:diagnostic imaging / Q000473:pathology; D018279:Carcinoma, Signet Ring Cell / Q000000981:diagnostic imaging / Q000473:pathology; D005188:False Negative Reactions; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007680:Kidney Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009852:Omentum / Q000000981:diagnostic imaging; D010534:Peritoneal Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary; D049268:Positron-Emission Tomography / Q000379:methods*; D011856:Radiographic Image Enhancement; D013274:Stomach Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology; D014057:Tomography, X-Ray Computed
D019788:Fluorodeoxyglucose F18