Assessment of pancreatic colloid carcinoma using 18F‑FDG PET/CT compared with MRI and enhanced CT

: Pancreatic colloid carcinoma (CC) is a rare sub-type of pancreatic adenocarcinoma which has an improved prognosis compared with pancreatic ductal carcinoma. Consequently, the early detection of CC by imaging may be of great significance in guiding patient management and therapeutic decisions. The present study aimed to analyze 18F-FDG PET/CT findings of CC in comparison to MRI and CT. PET/CT findings in 5 patients with CC were retrospectively reviewed based on visual interpretation and semi-quantitative index of SUVmax and TNR. Four patients received dual-time-point PET/CT scans. Additionally, one patient underwent contrast-enhanced CT scan, one MRI, and three received both. A total of five lesions were detected in five patients. Visually, two cases presented with mild FDG uptake, two with moderate and one with high. The mean of SUVmax and TNR was 5.1±2.2 and 2.8±0.7, respectively. Compared with CCs with low SUVmax, CCs with high SUVmax were more aggressive. No distant metastases were observed in five cases. Among four patients with dual-time-point PET/CT imaging, SUVmax increased in three cases and decreased in one case. The mean early and delayed SUVmax were 4.2±1.1 and 4.7±1.9, respectively (P>0.05). Radiological findings mainly included septated cystic components, internal sponge-like contrast-enhancement, calcification and 'salt-and-pepper sign' on MRI T2-weighted imaging. Thus, PET/CT provided additional information on metabolic tumor activity as well as locoregional and distant staging, which are important prognostic markers and may improve further patient management. However, PET/CT did not show any findings in addition to MRI and contrast-enhanced CT that were unique to CC and allowed a clear differentiation from other pancreatic malignancies.