To evaluate the differential diagnostic value of ¹⁸F-FDG PET/CT between pancreatic lymphoma(PL) and pancreatic carcinoma(PC).

The ¹⁸F-FDG PET-CT data of 16 patients who were pathological diagnosed with PL were retrospectively reviewed and compared with those of 32 consecutive pancreatic cancer patients who were pathologically diagnosed and randomly enrolled. The age, location, diameter and the maximum standard uptake values (SUV_max) of pancreatic lesions, pancreatic ductal dilatation, distal pancreatic atrophy, serum CA19-9 level and extrapancreatic organs involvement were analyzed.

The 16 patients with PL included 8 men and 8 women, the mean age was (46±17)year, and 11.1%(1/9) patients had elevated CA19-9. The 32 patients with PC included 15 men and 17 women, the mean age was (61±12)year, and 81.3% patients had elevated CA19-9. There were no significant differences on gender between the two groups, while the mean age of PL patients was younger than that of PC, elevated CA19-9 was less common than that in PC, and the differences were statistically significant (all P<0.05). There were 12 cases of diffusive large B cell lymphoma, 2 cases of B lymphoblastic lymphoma /leukaemia, 1 case of follicular lymphoma and 1 case of dysplastic large T cell lymphoma in 16 PL patients. There was no significant difference on the site of pancreatic lesions between the two groups , but long diameter of PL lesions was larger than that of PC [(6.6±3.3)vs(4.3±1.8)cm, P=0.038]. Dilated pancreatic duct and distal parenchyma atrophy in PL were less than those in PC (3/16 vs 17/32, 1/16 vs 13/32), and SUV_max of PL lesions was significantly higher than that of PC (12.0±5.5 vs 8.6±3.8), indicating that the differences were statistically significant (all P<0.05). The cut-off value of SUVmax was 9.95, and Youden′s index was 0.406 with the sensitivity and specificity of 68.8% and 71.9% for differentiating PL from PC. The incidence of extrapancreatic lesions including bone marrow and kidney and spleen infiltration was significantly more frequent in patients with PL than that in patients with PC(56.3% vs 6.25%, 43.8% vs 3.1%, 50.0% vs 6.3%), while the incidence of liver metastases was significantly lower than that in PC (12.5% vs 5.0%), indicating that the differences were statistically significant (all P<0.01). There were no significant differences on the incidence of other extrapancreatic lesions.

PL should be considered in relatively younger patients and manifested as a bulky mass with significant FDG uptake and extrapancreatic involvement of bone, kidney and spleen but without distinct pancreatic ductal dilation or distal parenchymal atrophy or liver metastasis.

Lymphoma; Pancreatic neoplasms; Tomography, emission-computed; Tomography, X-ray computed; Deoxyglucose; Diagnosis, differential