CT imaging features of different histological grades of pancreatic neuroendocrine tumors / 中华放射学杂志

ABSTRACT

Objective To explore diagnostic value of multi-slice spiral CT imaging features with respect to pancreatic neuroendocrine tumors (pNET) of different histological grades. Methods A retrospective analysis of preoperative abdominal plain CT and dual-phased contrast-enhanced CT was performed in 21 patients (median age, 47 years;12 males and 9 females) with pathologically proven pNET. age, gender, endocrine function, location and size of lesion, cystic change or necrosis, completeness of capsule, calcification, dilation of pancreatic duct were evaluated.CT attenuation-related parameters (plain CT value, relative density index, and CT value, CT value difference, enhanced percentage and enhancement index on arterial and portal phase) of each tumor were measured or calculated. All tumors were pathologically classified into three histological grades (G1, G2 and G3) based on mitotic count and ki-67 index. Kruskal-Wallis test was performed to compare differences of age, gender, endocrine function, morphological features among different grades. CT attenuation-related parameters were evaluated using Kruskal-Wallis or one-way analysis of variance (ANOVA). Results Twenty four pNET foci [grade G1 (n=13), G2 (n=7) and G3 (n=4)] were seen in the 21 patients. The difference of age, gender among different grades demonstrated no statistical significance (P>0.05). Nine lesions of G1 and 1 lesion of G2 demonstrated endocrine function, and the difference of endocrine function among three grades was statistically significant (χ2=8.355,P=0.012). For G1, G2 and G3, 11, 5 and 2 lesions were seen in uncinate process, pancreatic head and neck, respectively while 2, 2 and 2 lesions in pancreatic body and tail, respectively. The median maximum diameter of pNET of G1, G2 and G3 was 1.5, 2.5 and 6.7 cm, respectively;For G1, G2 and G3, 13, 4 and 0 lesions demonstrated intact capsule, respectively while 2, 3, and 3 lesions cystic degeneration and necrosis, respectivel; 0, 2 and 2 lesions calcification,respectively, 0, 1 and 2 lesions dilation of pancreaticobiliary duct, respectively, 0, 1 and 4 lesions sign of malignancy, respectively. The difference of size of lesion, completeness of capsule, calcification, and dilation of pancreatic duct showed statistical significance (P0.05). In addition, pNET of different grades demonstrated similar density and relative density index on plain CT. Regarding CT value, CT value difference, enhanced percentage and enhancement index on arterial and portal phase, the pNET of G2 showed highest value, while pNET of G3 lowest value, however, the difference about CT attenuation-related parameters among three grades showed no significant difference (P>0.05). Conclusion pNET of different histologic grades have some specific CT imaging features, which can facilitate an accurate diagnosis of pNET prior to therapy.