Acinar cell carcinoma of the pancreas presenting as diffuse pancreatic enlargement: Two case reports and literature review

Abstract

Rationale: Pancreatic acinar cell carcinoma (ACC) is a rare malignant tumor of exocrine pancreas. It is typically a well-marginated large solid mass arising in a certain aspect of the pancreas. Diffuse involvement of ACC in the pancreas is very rare, and may simulate pancreatitis in radiological findings. We report 2 cases of ACC presenting as diffuse enlargement of the pancreas due to tumor involvement without formation of a distinct mass.

Patient concerns: The patients consisted of a 41-year-old man with weight loss and a 77-year-old man who was asymptomatic.

Diagnoses: Computed tomography (CT) and 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT showed diffuse enlargement of the pancreas forming a sausage-like shape with homogenously increased FDG activity.

Interventions: Endoscopic ultrasound (EUS)-guided fine needle aspiration (FNA) biopsy of the pancreatic lesion was performed.

Outcomes: Histopathology results from the pancreas confirmed the diagnosis of pancreatic ACC.

Lessons: Because diffuse enlargement of the pancreas is a common imaging feature of pancreatitis, recognition of this rare morphologic pattern of ACC is important for radiological diagnosis of this tumor.

Figure 1

(A, B) Initial FDG PET/CT. The PET (A) and coregistered CT (B) revealing a sausage-like pancreas with homogenous accumulation of FDG. (C–F) Follow-up images after 5 months. FDG PET/CT fusion images showing progressive enlargement of the pancreas with increased FDG uptake (C) and hypermetabolic lesion in the portal vein suggesting tumor thrombus (D, arrow). Contrast-enhanced CT revealing heterogeneous enhancement of the pancreas (E) and multiple filling defects in the intrahepatic branch of the portal vein (F, arrows).

Figure 2

(A) Arterial phase of contrast-enhanced CT showing diffuse enlargement of the pancreas with a clear margin, forming a sausage-like shape. The enhancement was heterogeneous in the pancreas with multiple hypoattenuating cystic areas. (B) Axial PET/CT fusion image revealing diffuse enlargement of the pancreas with markedly increased radioactivity. The SUVmax was 9.4 in the pancreas. (C) The maximum intensity projection of PET image demonstrating diffuse and intense FDG uptake involving the entire pancreas from the uncinate process to the pancreatic tail.