A case of pancreatic hamartoma with characteristic radiological findings: radiological-pathological correlation

A case of solid-type pancreatic hamartoma presenting high apparent diffusion coefficient value: histopathological correlation and literature review

Pancreatic hamartoma is a rare tumor-like malformation and could mimic other pancreatic tumors including malignant neoplasm. Due to its rarity, magnetic resonance (MR) imaging findings including those diffusion-weighted (DW) imaging have not been clarified. We present a curious case of pancreatic hamartoma presenting high apparent diffusion coefficient (ADC) value with histopathological correlation. A 49-year-old woman with a pancreatic mass found incidentally on ultrasonography for medical checkup was referred to our institution for further examination and treatment because it slightly enlarged in the follow-up examination. Contrast-enhanced computed tomography (CT) and gadoxetic acid disodium-enhanced MR imaging revealed a well-demarcated solid mass of 13 mm in diameter in the pancreas body, which was gradually and homogeneously enhanced in the delayed/transient phase. It showed hyper intensity on T2-weight and DW images, and the mean ADC value was high (1.86 × 10^-3mm²/s). Laparoscopic distal pancreatectomy was conducted with suspicious preoperative diagnosis of pancreatic hypovascular neuroendocrine neoplasm (NEN). Histologically, the mass consisted of many disarranged small ducts without atypia embedded in abundant fibrous stroma and contained scant fatty tissue in the periphery, which was not identified on CT and MR images. There were no islets and peripheral nerves throughout the mass. Finally, it was pathologically diagnosed as a solid-type pancreatic hamartoma. Based on radiological-pathological correlation, it was considered that the abundant fibrous stroma and both the widely distributed myxomatous periductal stroma and scattered edematous stroma corresponded with delayed homogenous enhancement on CT/MR images and high ADC value, respectively. Although it is difficult to distinguish solid-type pancreatic hamartoma from other solid pancreatic neoplasms including hypovascular NEN on the basis of usual radiological findings, the high ADC value reflecting the specific pathology may be helpful for the differential diagnosis.

Pancreatic Hamartoma Difficult to Diagnose Preoperatively

Abdominal ultrasonography in a 70-year-old woman showed a hypoechoic mass, 14 mm in diameter, in the pancreatic body. Computed tomography showed a mass with contrast effect in the pancreatic body. Test results for endocrine factors or tumor markers were normal. The initial consideration was nonfunctional pancreatic neuroendocrine tumor. Over 8 years of monitoring, the tumor diameter increased to 18 mm, until pancreatic tumor enucleation was performed. The postoperative diagnosis was pancreatic hamartoma, a rare type of benign pancreatic tumor. The preoperative diagnosis of pancreatic hamartoma is difficult, but consideration must be given to the possibility of hamartoma when encountering pancreatic tumors.