ADC values of pancreas duct cancer are lowest.
Case 320
【Discussion】
Pancreatic carcinoma is most sensitive to visualized as non-enhanced tumor in arterial phase rather than non-enhanced, portal phase or capillary phase on CT. Meanwhile, Diffusion WI sequence is more sensitive to visualize pancreas carcinoma as high signal intensity rather than T1WI, T2WI and fat-suppression T2W on MRI. In our Case 2 (Fig.2), arterial phase on CT and Diffusion WIMRI are sensitive to demonstrate the presence of pancreatic cancer rather than other phases or other sequences.
It might be confusing to ADC values for differentiation between pancreas ductal adenocarcinoma and mass-forming chronic pancreatitis. However, it should be one of indicators to help to differentiate them.
First, ADC values of normal pancreas are reported to be over 1.4. However, as experienced on CT images interpretation, pancreas form and size vary, indicating to include factors of lipid infiltration or atrophic change. Actually, ADC values of pancreas parenchyma are reported to vary from 1.4 to 1.7 (1).
Meanwhile, ADC values of pancreatitis are reported to be 1.1 to 1.32 but those of mass-forming chronic pancreatitis are done to be 0.94 (2-6). This difference is considered probably due to difference of causes. Pancreatitis arises most from regurgitation of pancreatic juice, but small percentage of pancreatitis come from autoimmune pancreatitis with immune cells with lymphocytes and plasma cells. From my experiences, lymphocytes accumulation make ADC values decrease: ADC values of malignant lymphoma are around 0.5 and those of lymphoepithelial tumor of pancreas, around 0.7. Then, it indicates that pancreatitis with infiltration of lymphocyte tends to decrease ADC values. Namely, ADC values of conventional pancreatitis 1.1 to 1.3 and those of autoimmune pancreatitis are 0.9 to 1.0 (1-6). Then, ADC values on pancreatis vary from 0.9 to 1.32.
Further, ADC values of pancreas ductal adenocarcinoma (PDA) are reported to be 1.13 (1, 3, 4, 6). This value is basically important to differentiate PDA from normal parenchyma. But it might be difficult to differentiate PDA from pancreatitis because those of pancreatitis vary, indicating to include 1.1 level pancreatitis. Surprisingly, ADC vales of mass-forming chronic pancreatitis decrease to 0.9 (1), lower to those of PDA. That is probably because that mass-forming pancreatitis include lymphocyte accumulation.
However, although ADC values of 1.1 on mass are difficult to distinct between PDA and mass forming chronic pancreatitis or pancreatitis, ADC values of 1.2 or greater or those of 1.0 or less might be possible to differentiate pancreatitis from PDA.
To be a little tricky, pancreas cancer is categorized from PDA and adenocarcinoma from IPMN. Although ADC values of PDA were 1.1(1, 3) level but adenocarcinoma from IPMN are 1.2 to 1.3. Adenocarcinoma from IPMN arises via process from aplasia to highly differentiated, moderately differentiated, implying its ADC values are varying dependent on tumor growth process.
In our Case 1 with PDA whose ADC values are 1.163 on pancreatic tail cancer and those of liver metastases, 1.054, while Case 2 with adenocarcinoma from IPMN whose ADC values are 1.3-1.5.
【Summary】
We presented two cases with pancreas carcinoma: one, ductal adenocarcinoma and another adenocarcinoma from IPMN, whose ADC values are 1.163 and 1.3 – 1.5, respectively. It is borne in mind that ADC values of pancreas ductal adenocarcinoma were around 1.1 and those of pancreas carcinoma from IPMN were 1.2 -1.3 probably because pancreas adenocarcinoma from IPMN are mixed with aplasia, highly differentiated adenocarcinoma and moderately differentiated adenocarcinoma. Further, ADC values of pancreatitis vary from 0.9 to 1.3 probably because that pancreatitis vary from conventional pancreatitis to autoimmune pancreatitis. Surprisingly, ADC values of mass forming chronic pancreatitis are lower than pancreas ductal adenocarcinoma. Then, except adenocarcinoma from IPMN, ADC values of pancreas ductal adenocarcinoma are around 1.1, while those of pancreas parenchyma are around 1.4 or greater.
【References】
1.Schima W, et al. Mass-forming pancreatitis versus pancreatic ductal adenocarcinoma: CT and MR imaging for differentiation. Cancer Imaging. 2020: 20, Article number: 52
2.Wakabayashi T, et al. Clinical and imaging features of autoimmune pancreatitis with focal pancreatic swelling or mass formation: comparison with so-called tumor-forming pancreatitis and pancreatic carcinoma. Am J Gastroenterol. 2003;98:2679–87.
3.Choi SY, et al. Differentiating mass-forming autoimmune pancreatitis from pancreatic ductal adenocarcinoma on the basis of contrast-enhanced MRI and DWI findings. AJR Am J Roentgenol. 2016;206:291–300.
4.Kwon JH, et al. Differentiating focal autoimmune pancreatitis and pancreatic ductal adenocarcinoma: contrast-enhanced MRI with special emphasis on the arterial phase. Eur Radiol. 2019;29:5763–71.
5.Chang WI, et al. The clinical and radiological characteristics of focal mass-forming autoimmune pancreatitis: comparison with chronic pancreatitis and pancreatic cancer. Pancreas. 2009;38:401–8.
6.Muhi A, et al. Mass-forming autoimmune pancreatitis and pancreatic carcinoma: differential diagnosis on the basis of computed tomography and magnetic resonance cholangiopancreatography, and diffusion-weighted imaging findings. J Magn Reson Imaging. 2012;35:827–36.
2023.12.25