Pancreas
Tumors
Acinar cell cystadenoma / Acinar cystic transformation

Author: Brian S. Robinson M.D., Ph.D. (see Authors page)
Editor: Alyssa Krasinskas, M.D.

Revised: 24 January 2017, last major update January 2017

Copyright: (c) 2001-2017, PathologyOutlines.com, Inc.

PubMed search: acinar cell cystadenoma pancreas

Cite this page: Acinar cell cystadenoma / Acinar cystic transformation. PathologyOutlines.com website. http://pathologyoutlines.com/topic/pancreasacinarcellcystadenoma.html. Accessed September 20th, 2017.
Definition / general
  • Rare benign cystic lesion of the pancreas at least focally lined by benign, often attenuated, acinar cells
Essential features
  • First described in 2002 (Am J Surg Pathol 2002;26:698); recognized by WHO in 2010
  • Clinically indolent; no cases of metastasis have been reported
  • Most cases found incidentally, though may be symptomatic
  • Mitoses, atypia and necrosis are absent
Terminology
  • Other names include acinar cell transformation, acinar cystic transformation
Epidemiology
  • Rare, less than 100 cases reported in the English literature
  • In reported cases, female predominance with no age predilection
Sites
  • Found in all sites of the pancreas, with slight predominance for the head
Etiology
  • Favored to represent benign nonneoplastic distention of acinar units that can coalesce to form large cystic structure(s) (Am J Surg Pathol 2013;37:1329)
  • No longer thought to represent the benign counterpart to acinar cell cystadenocarcinoma
Clinical features
  • Often found incidentally on imaging
  • Most common clinical presentation is abdominal discomfort
Diagnosis
  • Requires clinical, radiologic and pathologic correlation
Radiology description
  • Nonspecific but the presence of five or more cysts, clustered peripheral small cysts, presence of cyst calcifications and absence of communication with the main pancreatic duct are supportive (Eur Radiol 2014;24:2128)
Case reports
Treatment
  • Typically surgically resected for symptomatic relief or to exclude other cystic neoplasms associated with malignancy
Gross description
  • Unilocular or multilocular cystic lesion found within head, body or tail of pancreas that ranges from 2 - 15 cm in size
  • Cysts contain clear white serous fluid and are lined with smooth, glistening walls
  • Solid areas or papillary excrescences on cyst wall are typically absent (rare cases with mural nodules have been reported)
  • Typically does not communicate with ductal system, though rare cases have been reported
Gross images

Images hosted on other servers:

Gross findings in acinar cell cystadenomas

a) Raw specimen;
b) fixated and
cut specimen

Acinar cell cystadenoma - involving the entire length of the pancreas (left) and localized (right)

Microscopic (histologic) description
  • Cysts of variable sizes lined by bland flattened cuboidal acinar cells with apical granular eosinophilic cytoplasm and dense basophilic basal cytoplasm
  • Ductal epithelium can be admixed with the acinar cells
  • Cyst lining may show focal mucinous or clear cell change
  • Smaller cysts of multilocular cysts may arise within separate adjacent lobules
  • Cysts may contain dense eosinophilic lamellar concretions
  • Nuclei may show prominent nucleoli
  • Mitotic activity is inconspicuous and nuclear atypia is minimal
  • There is no ovarian type stroma, necrosis or infiltrative growth
  • Background pancreas typically lacks pancreatic intraepithelial neoplasia and features of pancreatitis
Microscopic (histologic) images

Images hosted on PathOut server:

Case of the Week #136:

Various images



Images hosted on other servers:

Microscopic specimen - low (a) and high (b) magnification

Histological observations in acinar cell cystadenomas

Small acinar cell cystadenoma

Cystic structures lined by acinar cells

Cytology description
  • Smears usually low cellularity, containing cells resembling benign acinar or ductal epithelial cells
  • Smears often nondiagnostic due to limited cellularity
  • Eosinophilic concretions can mimic mucinous secretions
Positive stains
  • Trypsin, chymotrypsin, lipase, CAM 5.2, CK7, CK8, CK18
  • Apical cytoplasm with PAS positive, diastase resistant granules
  • CK19 will stain intervening patches of the ductal epithelium
Negative stains
Molecular / cytogenetics description
Differential diagnosis
  • Cystic variant of acinar cell carcinoma (acinar cell cystadenocarcinoma)
    • May have similar histology, but mitotic activity is conspicuous and there is clear atypia
  • Intraductal papillary mucinous neoplasms
    • Mucinous, papillary lining and connection to ductal systems favors IPMN
  • Mucinous cystic neoplasm
    • Ovarian type stroma is diagnostic; absent in cystic acinar cell lesions
    • Cyst lining is typically mucinous but may be nonmucinous; does not contain acinar cells
  • Serous cystadenoma
    • Areas with attenuated cytoplasm may mimic acinar cell cystadenoma
    • Serous cystadenoma contains rich subepithelial vascular network, which is typically absent in acinar cell cystadenoma
    • Should be negative for trypsin
  • Squamoid cyst of pancreatic ducts
    • Cystically dilated ducts are lined by a squamous / transitional epithelium, not acinar cells
    • May contain acidophilic concretions
Additional references