Value of 18FFDG PET/CT examination in the differential diagnosis of gastric cancer and primary gastric lymphoma

Objective:To explore the value of 18Ffluorodeoxyglucose (¹⁸F-FDG) PET/CT examination in the differential diagnosis of the gastric cancer and primary gastric lymphoma (PGL).
Methods:The clinical data of 80 patients with gastric cancer (60 with nonmucinous adenocarcinoma and 20 with mucinous adenocarcinoma) and 47 patients with PGL ［22 with mucosaassociated lymphoid tissue (MALT) and 25 with diffuse large Bcell lymphoma (DLBCL)］ who were admitted to the Tianjin Medical University Cancer Institute and Hospital from June 2006 to May 2014 were retrospectively analyzed. Spiral CT scan was first done and then followed by PET.The CT value of the lesions, maximum standardized uptake value (SUVmax) of patients and maximal gastrointestinal wall thickness (THKmax) were analyzed by the ANOVA test. The SUVmax comparison between groups was evaluated with the StudentNewmanKeuls. The lesions type was analyzed by the chisquare test. The THKmax and SUVmax among groups were analyzed by the Pearson correlation analysis.
Results:¹⁸F-FDG PET/CT imaging of patients with gastric cancer and PGL showed different types of gastric wall thickening, segmental and limited thickening of gastric wall were the main features of gastric cancer and diffuse and segmental thickening of gastric wall were the main features of PGL. The type Ⅰ, Ⅱ and Ⅲ of lesions were detected  in 12, 21 and 27 of 60 patients with nonmucinous adenocarcinoma, in 2, 7 and 11 of 20 patients with mucinous adenocarcinoma, in 8, 8 and 6 of 22 patients with MALT and in 13, 7 and 5 of 25 patients with DLBCL respectively. There were significant differences in the 4 pathological types of lesions among all the patients (χ²=14.849, P<0.05). The lymph nodes beneath the renal hilum and at the retroperitoneum were involved in 16 patients with gastric cancer and in 10 patients with PGL, and 7 patients with gastric cancer and 12 patients with PGL were complicated with splenomegalia, respectively, showing a significant difference in the splenomegalia between patients with PGL and gastric cancer (χ²=7.506, P<0.05). There was no significant difference in the metastasis of lymph nodes beneath the renal hilum and at the retroperitoneum between patients with PGL and gastric cancer (χ²=0.178, P>0.05). Among 80 patients with gastric cancer, positive ¹⁸F-FDG was detected in 79 patients and negative ¹⁸F-FDG in 1 patient with T3 stage of mucinous adenocarcinoma. Among 47 patients with PGL, positive 18FFDG was detected in 46 patients and negative ¹⁸F-FDG in 1 patient with stage Ⅰ of MALT. The CT value of the lesion, SUVmax and THKmax in patients with nonmucinous adenocarcinoma,  mucinous adenocarcinoma, MALT and DLBCL were (40±8)HU, (39±11)HU,  (41±11)HU, (38±9)HU and 9.9±6.6, 5.6±1.9, 4.6±2.9, 18.3±7.6 and (2.1±1.2)cm, (1.9±0.9)cm, (1.3±1.1)cm and (2.6±1.5)cm, respectively, showing significant differences in the SUVmax among all the groups (F=26.920, P<0.05). In the pairwise comparisons, there were no significant difference between the MALT group and mucinous adenocarcinoma group (P>0.05), and significant differences among the other groups (P<0.05). The CT value of the lesions and THKmax among all the patients were compared, with no significant differences (F=0.578, 4.510, P>0.05). There were no significant differences in the SUVmax and THKmax among all the patients (r=0.055, 0.346, 0.226, 0.133, P>0.05).
Conclusions There is an important diagnosis value of PET/CT examination in patients with gastric cancer and PGL. The pathological types of the lesions in patients with gastric cancer and PGL are different. The occurrence of splenomegalia in patients with PGL is easier than that with gastric cancer. SUVmax of patients with DLBCL is higher than those with gastric cancer and MALT. FDG uptake in patients with mucinous adenocarcinoma and MALT are not enough, and these may lead to false negative result of PET/CT examination.