Probable imaging findings of mass-forming pancreatitis
Case 321
【Discussion】
Pathological microscopy revealed cardinal findings of chronic pancreatitis are loss of pancreatic acinar cells, duct changes of stenosis and/or ectasis and fibrosis, indicative of non-specific characteristics (1, 2). Pancreatitis arises from non-specific causes of alcohol, fat-containing food and from immunological factor such as Ig G4. Mass-forming pancreatitis is also emerging from various factors. Mass formed in pancreatitis composes of accumulation of lymphocytes (mainly plasma cells) and macrophages, and fibrosis by fibrocytes (3, 4).
Cardinal findings to differentiate mass formed in pancreatitis from pancreatic duct cancer are duct-penetrating sign, slightly high signal intensity on T1WI, relatively low signal intensity on T2WI, high signal intensity on Diffusion WI and lowering value on ADC map (5-7). Of these, the finding of duct-penetrating sign is most accepting for determining mass-forming pancreatitis probably because other three findings are not so often encountered (5). However, in our case duct-penetrating sign was not found but the other three findings met.
ADC values of chronic pancreatitis vary from 0.8 to 1.2, while those of pancreas duct cancer were around 1.1 (7). ADC values of conventional pancreatitis are reported to be 1.0 to 1.2 and those of auto-immune pancreatitis, 0.8 to 0.9 (7). Then, it is hard for distinct between them by measuring ADC values because of their overlapping. However, it might be able to state that ADC values over 1.1 or below 1.1 reflect mass formed by pancreatitis.
In our case, ADC values of mass formed by pancreatitis on the first MRI revealed 0.869 to 0.991 and those of the following year revealed rise to 1.142 to 1.261. This is probably because the component of the mass changes to increase fibrotic change rather than pure accumulation of immune cells of lymphocytes and macrophages as time progress. Further, our case with pancreatitis arises from alcohol rather than autoimmune. Despite this, ADC values were lowering to below 1.0 and one year later they rose to 1.1, indicating ADC values change to rise probably reparative process advances.
Then, if we encountered pancreas mass whose ADC values were around 1.1, we would be in an equivocal position to interpret it pancreas cancer or mass formed by pancreatitis. In this situation, multidisciplinary diagnostic tools such as patient history, laboratory test of amylase, CEA and CA 19-9 are necessary to make an appropriate diagnosis. It might be thoughtful not to determine it pancreas cancer, even though its ADC values were 1.0 level.
【Summary】
We presented a sixty-four-year-old male with consistent left back pain whose past illness history indicated repeated chronic pancreatitis stemmed from massive-volume alcohol drinking. Laboratory data revealed elevation of P-type amylase values. MRI depicted relatively high signal intensity on T1WI, relatively low signal intensity on T2WI, relatively high signal intensity on Diffusion WI, ADC values lower, 1.142 – 1.261. One year before when pancreatitis occurred, ADC values were 0.869 – 0.991.
It is borne in mind that ADC values of mass formed by pancreatitis can change from 0.8 to 1.2 level, overlapping 1.1 level of pancreatic duct cancer. When we encounter pancreas mass whose ADC values are around 1.1 for the first time, multidisciplinary diagnostic tools such as patient history, laboratory test of amylase, CEA and CA 19-9 associated with imaging on MRI with T1WI and T2 WI, are necessary to make an appropriate diagnosis.
【References】
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6.Schima W, et al. Mass-forming pancreatitis versus pancreatic ductal adenocarcinoma: CT and MR imaging for differentiation. Cancer Imaging volume 20, Article number: 52 (2020)
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2023.12.29