Diffusion‐weighted magnetic resonance imaging of pancreatic adenocarcinomas: Association with histopathology and tumor grade

Abstract

Purpose: To evaluate the utility of diffusion-weighted magnetic resonance imaging (DWI) in pancreatic ductal adenocarcinoma with various grades of differentiation. Materials and Methods:Following Institutional Review Board (IRB) approval, 21 consecutive patients with surgical pathology-proven pancreatic adenocarcinomas were retrospectively evaluated. Histopathologic characteristics and grades of differentiation of adenocarcinomas were analyzed. Twenty-one patients without a known history of pancreatic disease were evaluated as the control group. Anatomic MR images and DW images were acquired using 1.5-T MR systems. DWI with b values of 0 and 500 sec/ mm 2 were performed on both patients and control groups. The difference in mean apparent diffusion coefficient (ADC) values among groups of normal pancreatic parenchyma, adenocarcinomas with poor differentiation, and adenocarcinomas with well/moderate differentiation were compared using one-way analysis of variance.Results: Mean ADCs of pancreatic adenocarcinomas (1.77 6 0.45 Â 10 À3 mm 2 /sec) was not significantly lower than that of normal parenchyma (1.98 6 0.31) (P ¼ 0.09). When adenocarcinomas were subdivided based on grades of differentiation, however, poorly differentiated adenocarcinoma with histopathologic characteristics of limited glandular formation and dense fibrosis had significantly lower ADCs (1.46 6 0.17) compared to those of well/moderately differentiated adenocarcinomas (2.10 6 0.42) characterized by neoplastic tubular structures (P < 0.01). Well/moderately differentiated adenocarcinomas with dense fibrosis showed significantly lower ADC values (1.49 6 0.19) than those with loose fibrosis (2.26 6 0.30) (P ¼ 0.01).Conclusion: Difference in ADC values using DWI between poorly and well/moderately differentiated pancreatic ductal adenocarcinoma may relate to differences in glandular formation and density of fibrosis.

Prognostication and response assessment in liver and pancreatic tumors: The new imaging

“…Details on the most relevant published studies are reported in Table 2. Overall, low-grade PDACs tend to present low ADC values [43][44][45] , but it still not clear which histological feature mainly contributes to diffusion restriction. Wang et al [43] and Muraoka et al [46] reported that tumors with limited glandular formation and dense fibrosis (i.e., paucicellular tumors) had lower ADC values as compared to welldifferentiated lesions characterized by neoplastic tubular structures; moreover, PDACs with dense fibrosis showed significantly lower ADC values than those with loose fibrosis.…”

“…Overall, low-grade PDACs tend to present low ADC values [43][44][45] , but it still not clear which histological feature mainly contributes to diffusion restriction. Wang et al [43] and Muraoka et al [46] reported that tumors with limited glandular formation and dense fibrosis (i.e., paucicellular tumors) had lower ADC values as compared to welldifferentiated lesions characterized by neoplastic tubular structures; moreover, PDACs with dense fibrosis showed significantly lower ADC values than those with loose fibrosis. Fibrosis may be therefore the key factor contributing to diffusion restriction in PDACs, but these findings have not been confirmed by other studies: particularly, Klauss et al [47] reported that the difference between the IVIM-derived D value (diffusion) of moderate and severe fibrosis PDACs was significant, but the cellular complexes surrounded by fibrosis formed only on solid areas showing diffusion restriction.…”

“…Surgical resection is the only curative treatment for this neoplasm, therefore the preoperative prediction of the pathological grade may have a smaller importance for PDAC management as compared to other pancreatic tumors. Some studies have tried to correlate DWI findings with the pathological grade, but results are controversial [43][44][45] . Details on the most relevant published studies are reported in Table 2.…”

“…Etchebehere et al [67] compared WBDWI with 68 Ga-DOTATATE PET-CT and 99mTc-HYNICOctreotide SPECT-CT: WBDWI had a similar accuracy when compared to molecular imaging techniques for lung and liver lesions, while showed a higher false-negative rate for bone lesions. Schraml et al [68] reported that PET-CT and WBDWI had comparable overall detection rates for NETs metastases but Wang et al [43] 21 0, 500 PDAC 2.10 (WD-MD); 1.46 (PD) Legrand et al [44] 22 Wang et al [58] 18 0, 50, 500 PanNET 1.75 (G1); 1.00 (G3) Jang et al [59] 20 0, 800 PanNET 1.48 (G1-G2); 1.04 (G3) Hwang et al [60] 44 significantly differed in organ-based detection rates with superiority of PET-CT for lymph node and pulmonary lesions and of WBDWI for liver and bone metastases. Experimental applications of pCT to PanNETs reported interesting results.…”

Impact of field strength and RF excitation on abdominal diffusion-weighted magnetic resonance imaging

“…The technique may be useful in determining pathology in the liver (degree of cirrhosis/fibrosis), kidneys (lesion characterization, renal failure, pyelonephritis), pancreas (pancreatitis and pancreatic cancer), bowel (Crohn's disease), and uterus (endometriosis) [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] . In a recent meta-analysis, Li et al [19] has shown a potential future role for this type of sequence to assess for cancers within the liver.…”