Pancreas
Acinar cell tumors
Acinar cell carcinoma
Author: Deepali Jain, M.D.
Topic Completed: 1 August 2012
Minor changes: 6 March 2020
Copyright: 2002-2020, PathologyOutlines.com, Inc.
PubMed Search: Acinar cell carcinoma[TI] pancreas[TI]
Table of Contents
Definition / general | Clinical features | Case reports | Gross description | Gross images | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Cytology images | Positive stains | Negative stains | Electron microscopy description | Electron microscopy images | Molecular / cytogenetics description | Differential diagnosisCite this page: Jain D. Acinar cell carcinoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/pancreasacinar.html. Accessed August 10th, 2020.
Definition / general
- Malignant epithelial neoplasm composed of cells with morphological resemblance to acinar cells and with evidence of pancreatic exocrine enzyme production (IARC: 8550 / 3 Acinar Cell Carcinoma [Accessed 12 December 2017])
- Resembles similar tumor in parotid gland
- 1 - 2% of pancreatic malignancies
Clinical features
- 85% men; mean age 62 years (range, 40 - 81 years), rare in children (Am J Surg Pathol 1992;16:815)
- 10% have lipase hypersecretion syndrome (subcutaneous fat necrosis, polyarthralgias, occasional eosinophilia, nonbacterial thrombotic endocarditis) due to tumor lipase secretion by tumor; these patients usually have liver metastases
- Tumors may also secrete alpha fetoprotein (AFP) and most AFP+ pancreatic neoplasms are acinar cell carcinomas or pancreatoblastoma (Hum Pathol 2000;31:938)
- 50% have metastases at diagnosis (liver and regional lymph nodes)
- 5 year survival is only 10%
- Variant with intraductal polypoid growth: less aggressive behavior, fewer metastases, smaller size (Am J Surg Pathol 2010;34:1025, Int J Surg Pathol 2011;19:795)
- Poor prognostic factors: stage III / IV versus I / II (Am J Surg Pathol 2012;36:1782)
Case reports
- 44 year old woman with pancreatic mass (Arch Pathol Lab Med 2002;126:985)
- 50 year old man (Arch Pathol Lab Med 2001;125:1127)
Gross description
- Well circumscribed, soft / fleshy (since minimal stroma) with fibrous septa, large (mean 11 cm), hemorrhage and necrosis common
Gross images
AFIP
Cut surface displays large nodules separated by fibrous strands, with frequently necrotic foci
Microscopic (histologic) description
- Note: must document pancreatic enzymes to be considered an acinar cell tumor
- Highly cellular with minimal stroma and no desmoplasia
- Solid, nesting, glandular or acinar patterns with sharp luminal space outlines
- Monotonous, uniform polarized cells with abundant eosinophilic granular apical cytoplasm due to zymogen granules (scanty in solid tumors), basal nuclei and single prominent nucleoli
- Moderate nuclear atypia, variable mitoses, no mucin
- Vascular invasion often present
- 30 - 50% have minor endocrine component based on immunohistochemistry
- Tumors with solid or trabecular pattern resembles endocrine tumors
Microscopic (histologic) images
AFIP
Mixture of acinar, trabecular and solid patterns
Pure acinar pattern resembles normal pancreas
Tumor is markedly cellular with gross lobulation by broad fibrous strands; stroma is scant within large tumor lobules
Nuclei are somewhat irregular in size; nuclei are polarized in acinar formations
Dilated acini form "microglandular" structures
Round cells with
scant cytoplasm,
slightly irregular
nuclei, distinct nucleoli
PAS: tumor cells have abundant, finely granular cytoplasm, which is PAS+ in apical portion
Trypsin stains tumor cells intensely (right side), normal acinar tissue is also typsin+ (right side)
Trypsin stains apical portion of tumor cells
CAM 5.2+
Synaptophysin+
Cytology description
- Small to moderate sized loose groups with numerous single cells, prominent acinar formation, little anisonucleosis and prominent nucleoli
- Background cleaner than ductal carcinoma
- Significant overlap with features of pancreatic endocrine tumors (Diagn Cytopathol 2006;34:367)
Cytology images
Images hosted on other servers:
FNA from metastases to liver
Positive stains
- Note: staining is often in the apical portion of the tumor cells
- BCL10 (Virchows Arch 2009;454:133), PAS (diastase resistant) for granules, trypsin and chymotrypsin (90%+ sensitive), lipase (50% sensitive), amylase, elastase, butyrate esterase (75% sensitive, indicates lipase), keratin, 2P-1-2-1 (sensitivity and specificity 100%, J Clin Pathol 2012;65:327)
- Claudin7 (Am J Surg Pathol 2009;33:768, Arch Pathol Lab Med 2008;132:490)
Electron microscopy description
- Well developed microvilli, abundant granular (rough) ER, numerous mitochondria, zymogen like granules (300 - 600 nm, apical, homogenous), irregular fibrillary granules (up to 3500 nm with fibrillary internal structures, resemble zymogen granules in developing pancreas)
Electron microscopy images
AFIP
Tumor cells have many pleomorphic and rather small zymogen granules (mean 400 - 500 nm, range 200 - 1000 nm), commonly oriented towards the luminal space; they are round and lack a hole between their homogeneous dark staining contents and the granule membrane
Images hosted on other servers:
FNA from liver metastasis
Molecular / cytogenetics description
- Amplifications at chromosome 20q (100%) and 19p (80%) (Mod Pathol 2011;24:1229)
- Kras and p53 mutations uncommon
- Biallelic inactivation of LKB1 is associated with Peutz-Jeghers syndrome
Differential diagnosis
- Ductal adenocarcinoma: mucicarmine+, CEA+, negative for acinar markers
- IPMN: papillary variant of acinar carcinoma, compared to IPMN, has nodules with more sheetlike nature, cuboidal cells, basophilic cytoplasm, prominent nucleoli, apical granules, intraluminal crystals or pale, acidophilic secretions and lack of mucin (Am J Surg Pathol 2007;31:363)
- Pancreatic endocrine tumor: no acinar differentiation, uniform nuclear morphology, fibrous stroma, PAS-
- Pancreatoblastoma: children, squamoid bodies
- Solid pseudopapillary neoplasm: young women, cystic and hemorrhagic, solid and pseudopapillary patterns, CD56+, CD10+
