Acinar Cell Nodule of the Pancreas

Definition

Microscopic circumscribed nodule of acinar cells distinct from surrounding acini

Sharply demarcated aggregate
- Not encapsulated
0.2-0.5 mm diameter
- 80-150 cells in cross-section
Cells slightly larger than normal acinar cells
- Acidophilic type with apical zymogen granules
- Basophilic type with few granules
- Occasional vacuolar change
Nuclei similar to normal
- Usually basal
- Usually prominent nucleoli
- Infrequent mitotic figures
No clinical significance
- Reported in up to 44% of pancreata
- No evidence of progression to carcinoma
If cystic, see Acinar Cell Cystadenoma

Acinar Cell Nodule of the Pancreas	Islet Cell Hyperplasia / Aggregation
Usually prominent nucleoli	Salt and pepper chromatin
Trypsin, chymotrypsin, lipase positive	Chromogranin, synaptophysin positive

Both are of no clinical significance

Acinar Cell Nodule of the Pancreas	Pancreatic Neuroendocrine Microadenoma
Trypsin, chymotrypsin, lipase positive	Chromogranin, synaptophysin positive
Usually basal nuclei	Usually central nuclei
Usually apical granular eosinophilic cytoplasm	Usually scant cytoplasm

Both are of no clinical significance

Solcia E, Capella C, Kloppel G . Tumors of the Pancreas, Atlas of Tumor Pathology, AFIP Third Series, Fascicle 20, 1997.
Kishi K, Nakamura K, Yoshimori M, Tajiri H, Ozaki H, Kinoshita T, Kosuge T, Hayakawa M. Morphology and pathological significance of focal acinar cell dysplasia of the human pancreas. Pancreas. 1992;7(2):177-82.
Tanaka T, Mori H, Williams GM. Atypical and neoplastic acinar cell lesions of the pancreas in an autopsy study of Japanese patients. Cancer. 1988 Jun 1;61(11):2278-85.

Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342

Original posting/last update: 1/9/08, 12/28/13