Acinar Cell Carcinoma of the Pancreas
Definition
- Carcinoma of the pancreas exhibiting exocrine differentiation and lacking significant (<25%) ductal or endocrine differentiation
Alternate/Historical Names
- Acinic cell carcinoma
- (Note that solid-pseudopapillary neoplasm was erroneously considered in some early reports to be acinar and designated cystic acinar cell carcinoma)
Diagnostic Criteria
- Usually grossly circumscribed
- May have pseudocapsule
- Frequently has lobular growth pattern
- Scant stroma within lobules
- Lacks desmoplastic stroma of ductal adenocarcinoma
- Most common growth patterns are solid and acinar
- Solid pattern
- Sheets and nests of cells
- May be mixed with acinar pattern
- Acinar pattern
- Small lumens surrounded by cells with basal nuclei
- Glandular and trabecular patterns may occur
- Cystic variant
- Innumerable variably sized cysts
- Termed acinar cell cystadenocarcinoma
- Intraductal / papillary variant
- Associated with cystic dilation of ducts
- Reported cases have better survival
- Solid pattern
- Moderate to abundant granular eosinophilic cytoplasm
- PAS positive diastase resistant
- May be minimal in some cases
- Usually apical
- PAS positive diastase resistant
- Uniform vesicular nuclei
- Large central single nucleolus
- Usually only moderate nuclear pleomorphism
- Cases with large pleomorphic cells have been reported
- No clinical significance
- Cases with large pleomorphic cells have been reported
- Mitotic figures frequent in most cases
- Nuclei frequently basally located
- Invasion usually present
- Vascular and perineural invasion common
- May invade adjacent tissues and organs
- Rare histologic variants
- Oncocytic
- Signet ring
- Clear cell
- Spindle cells (focal)
- Recognized as acinar based on architectural pattern, nuclear features and presence of classical acinar appearance in other areas
- Mixed differentiation may occur
- Each component must comprise at least 25% of the tumor
- Behavior for mixed neoplasms is similar to pure acinar cell carcinoma
- Mixed acinar-endocrine requires immunohistochemistry for recognition
- Mixed acinar-ductal or mixtures of all three may occur
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting/updates:1/2/08, 1/2/12, 2/17/13
