Intense PET Signal in the Degenerative Necrosis Superimposed on Chronic Pancreatitis

Abstract

Although fluorine-18 deoxyglucose-positron emission tomography (FDG-PET) is a sensitive diagnostic modality in detecting malignant tumors, differential diagnosis of malignant tumors from inflammatory lesion is challenging. We experienced a case of acute degenerative necrosis superimposed on chronic pancreatitis, which was difficult to distinguish from pancreatic cancer. The patient was a 66-year-old man with a complaint of upper abdominal pain. Abdominal computed tomography revealed low-density masses in the head and body of the pancreas. FDG-PET revealed intense accumulations at the head and body of the pancreas (mean standard uptake value for the head and body pancreatic tumors was 4.1 and 6.7, respectively) corresponding to the 2 tumors detected by computed tomography. Because of a possible malignant pancreatic tumor, the patient underwent pylorus-preserving pancreatoduodenectomy. Histologic examination of the resected specimen revealed a characteristic of chronic pancreatitis in a nontumorous area. Two tumors detected by FDG-PET consisted of degenerative necrosis surrounded by granulation tissue. The amount of granulation tissue was correlated to the levels of standard uptake value. No malignant tumors were observed. This case suggests a limitation of FDG-PET in distinguishing malignant neoplastic lesions in the pancreas, especially from acute degenerative changes in chronic pancreatitis. Repetitive PET examination is recommended for the accurate diagnosis.

Preoperative evaluation of pancreatic adenocarcinoma

“…Conversely, false‐positive FDG‐PET results can be seen in inflammatory conditions, such as chronic pancreatitis. The SUV of pancreatic cancer is generally slightly higher than that seen in chronic pancreatitis, although the potential for false‐positive results is real ,. Delbeke et al reported an optimal cut off level of 2.0 for differentiating malignant from benign lesions, aiding in the differentiation of chronic pancreatitis from pancreatic cancer.…”

Differentiation of autoimmune pancreatitis from suspected pancreatic cancer by fluorine-18 fluorodeoxyglucose positron emission tomography

“…However, FDG-PET cannot always differentiate between such lesions 17,18 , since the inflammatory foci of the pancreas also accumulates FDG 19,20,21,22 . In addition, previous reports have shown that patients with autoimmune pancreatitis also show intense FDG uptake 19,23,24 .…”

Approaches to localized pancreatic cancer

“…For one, FDG uptake in tissues is not completely tumor specific and can be observed in inflammatory processes such as chronic pancreatitis, leading to false-positive results [35]. In addition, false-negative results have been reported in patients with hyperglycemia, as well as in patients with very early-stage cancer or well-differentiated tumors [35]. On the other hand, PET is inferior to CT in assessing surgical resectability because of its limited spatial resolution and the absence of anatomical landmarks.…”

“…Although FDG-PET can detect small intrapancreatic lesions that are not detected by CT and MRI, it is not routinely used for diagnosing primary pancreatic cancer. For one, FDG uptake in tissues is not completely tumor specific and can be observed in inflammatory processes such as chronic pancreatitis, leading to false-positive results [35]. In addition, false-negative results have been reported in patients with hyperglycemia, as well as in patients with very early-stage cancer or well-differentiated tumors [35].…”