Acinar cell carcinoma

Pancreas
Acinar cell tumors
Acinar cell carcinoma

Author: Deepali Jain, M.D.

Topic Completed: 1 August 2012

Revised: 6 March 2020

Copyright: 2002-2020, PathologyOutlines.com, Inc.

PubMed Search: Acinar cell carcinoma[TI] pancreas[TI]

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Table of Contents

Cite this page: Jain D. Acinar cell carcinoma. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/pancreasacinar.html. Accessed April 3rd, 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)

Negative stains

Mucin, CD56, PAX8

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+