A small pancreatic hamartoma with an obstruction of the main pancreatic duct and avid FDG uptake mimicking a malignant pancreatic tumor: a systematic case review
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Pancreatic hamartomas are extremely rare and may be misdiagnosed as malignant tumors. We report herein a case of a small, solid-type pancreatic hamartoma.
A 72-year-old female was incidentally detected pancreatic lesion by ultrasonography. Computed tomography and magnetic resonance imaging revealed a 2.0-cm solid lesion. The main pancreatic duct (MPD) was obstructed by the lesion in the head of the pancreas, and the upstream MPD was dilated. 18F-fluorodeoxyglucose (FDG) accumulated avidly in the lesion and increased in FDG intensity from the early to the delayed images. The histopathological studies confirmed the diagnosis of pancreatic hamartoma. Immunohistochemically, the cell membrane of the accessory glands and ducts showed homogeneous expression of glucose transporter type I and hexokinase II.
Pancreatic hamartomas causing dilatation of the MPD are extremely rare, and this appears to be the first case of a hamartoma to take up FDG avidly. It was a rare occurrence and should be noted that pancreatic hamartomas can cause an obstruction of the MPD and show avid FDG uptake, thereby mimicking malignant pancreatic tumors.
KeywordsHamartoma Pancreas CT MRI FDG PET/CT
Endoscopic retrograde cholangiopancreatography
Glucose transporter type I
Main pancreatic duct
Magnetic resonance imaging
Positron emission tomography/CT
Maximum standardized uptake value
Hamartomas are benign, tumor-like nodules composed of an overgrowth of mature cells and tissues that normally occur in the affected tissue, but often with one predominant element. Pancreatic hamartomas are composed of three disarranged cellular components in varying proportions: acinar, islet, and ductal cells . These hamartomas are extremely rare and may be misdiagnosed as malignant tumors. Herein, we report a case of pancreatic hamartoma resembling a malignant pancreatic tumor.
A 72-year-old asymptomatic woman was referred to our hospital for examination of a pancreatic lesion detected on abdominal ultrasonography during a health screening. Her past medical history and physical examination were unremarkable. On laboratory testing, the serum levels of amylase, bilirubin, carcinoembryonic antigen, and carbohydrate antigen 19-9 were within normal limits.
Pancreatic hamartomas are extremely rare, and their radiologic features have not been fully evaluated. To the best of our knowledge, there have been only 30 previous reports of pancreatic hamartomas in the literature, and there are very few reports regarding their imaging appearance [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]. Age at presentation ranged from 34 weeks to 78 years (mean, 48.6 years). Both sexes were equally affected, with a male-to-female ratio of 1:0.82. Most patients were either asymptomatic or they exhibited symptoms related to local mass effect, including abdominal pain, weight loss, and a palpable mass; and only one patient had jaundice, caused by obstruction of the common bile duct . Pancreatic hamartomas were reported to arise from all parts of the pancreas, although the pancreatic head was the most common site (64.5%, 20/31). Their size ranged from 1.0–14.0 cm (mean, 4.5 cm).
Morphologically, there are two types of pancreatic hamartoma: solid, and solid and cystic [2, 3]. Nine of the previously reported cases of pancreatic hamartoma seemed to fit the criteria of solid type; however, only three reports included the radiological appearance [1, 16, 17]. One showed that the MPD was compressed by the hamartoma located in the pancreatic body, and the upstream was dilated . The remaining two cases had no stricture or dilatation of the MPD [1, 17]. On enhanced CT, one case showed a hyperattenuating hamartoma during the portal venous phase , and the other two cases demonstrated delayed enhancement on contrast-enhanced CT or MRI [1, 16]. In the present case, a pancreatic hamartoma measuring 2.0 cm in diameter was located in the head of the pancreas and caused an obstruction of the MPD, with a dilated upstream on CT, MRCP, and ERCP. Contrast-enhanced CT demonstrated an ill-defined lesion with mild hypoattenuation during the pancreatic parenchymal phase and isoattenuation during the portal venous and delayed phases.
Pancreatic ductal adenocarcinomas may present as a non-deforming iso- or hypoattenuation mass during the pancreatic parenchymal to portal venous phase on enhanced CT , and have an obstruction of the MPD with upstream ductal dilatation on CT or MRI [21, 22]. Pancreatic neuroendocrine tumors usually show hypervascular patterns during the arterial to the portal venous phase. However, high-grade pancreatic neuroendocrine tumors tend to show hypovascular patterns and an interruption of the MPD with upstream ductal dilatation [23, 24, 25]. Therefore, in the present case, it was difficult to differentiate pancreatic hamartoma from ductal adenocarcinoma, neuroendocrine tumor, or pancreatic metastases.
On FDG-PET, no avid FDG uptake was noted in the three previously reported cases of pancreatic hamartoma [9, 14, 15]. Ours appears to be the first case of a pancreatic hamartoma to show avid FDG uptake, which may be related to the GLUT-1 and HK-II expression of the accessory glands and ducts. Yoshioka et al.  reported that an FDG SUVmax of 2.5 would be justified as a cut-off value to differentiate between malignant and benign pancreatic tumors. Kawada et al.  reported that the FDG SUVmax increased from the early to the delayed images in 89% (39/44) of the small malignant pancreatic tumors (< 25 mm). In the present case, the FDG SUVmax was 3.6 at the early phase and increased to 5.0 at the delayed phase, in concordance with malignant pancreatic tumors. In our case, therefore, it was difficult to differentiate from malignant tumors based on US, CT, MRI, and FDG-PET/CT findings. Pancreatic hamartoma is benign entity, and does not require surgical treatment. EUS-Fine-Needle-Aspiration might have been effective for definitive diagnosis if we had performed it.
Pancreatic hamartomas causing dilatation of the MPD were extremely rare, and showed no avid FDG uptake in the previously reported cases. We described a rare case of a small, solid-type pancreatic hamartoma that showed an obstruction of the main pancreatic duct and avid FDG uptake. Radiologists should be aware that pancreatic hamartomas may be associated with these findings.
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The datasets supporting the conclusions of this article are included within the article.
All authors participated in clinical examinations, diagnosis, surgical operation and follow up for of this patient. MN, YF, YK, AT and TY took part in the design of this study and helped to draft the manuscript. All authors read and approved the final manuscript.
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This case report was granted an exemption from requiring ethics approval by the Institutional Review Board of Nanpuh Hospital.
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