Definition
Microscopic noninvasive epithelial neoplasm arising in the pancreatic ducts
Alternate/Historical Names
Pancreatic intraepithelial lesion (sometimes used for grade 1 or 2 lesions)
PanIN
Diagnostic Criteria
Microscopic finding
Usually involves ducts <5 mm in diameter
Measure largest cross-section from basement membrane
Do not include periductal lesions or fibrosis
Measure entire duct even if only partially involved
Involved ducts >5 mm may be due to obstruction
Lined by columnar to cuboidal mucinous cells
Mucin may be depleted in high grade lesions
Varying degrees of cytologic atypia and architectural complexity
Reetesh Pai MD
Original posting : February 1, 2007
Supplemental studies
Immunohistology
Differential Diagnosis
Normal Duct
PanIN
Cuboidal to low columnar lining
Tall columnar lining
Amphophilic cytoplasm
Abundant supranuclear mucin
Regular bland nuclei
May show nuclear crowding and atypia
Reactive Duct
PanIN
Round smooth nuclei
Nuclei may show irregularity
Basally oriented nuclei
May have pseudostratified or stratified nuclei
Eosinophilic cytoplasm
Abundant supranuclear mucin
No micropapillary architecture
May be micropapillary
Cancerization of Duct by Invasive Ductal Carcinoma
PanIN, Grade 3
Abrupt transition of neoplastic to normal
Gradual transition
May be continuous with invasive carcinoma
Not continuous with invasive carcinoma
Intraductal Papillary Mucinous Neoplasm PanIN
Usually clinically detectable
Usually not clinically detectable
Grossly visible
Not grossly visible
May have well formed papillae
No well formed papillae
May be associated with colloid carcinoma
No association with colloid carcinoma
MUC2 or CDX2 may be positive
MUC2 and CDX2 negative
Clinical
PanIN 1A and 1B are common incidental findings
May be found in up to 40% of noncancerous pancreata
Natural history of PanIN 2 and 3 is not known
PanIN 3, at least, may be a precursor to invasive ductal carcinoma
Rare in noncancerous pancreata
Present in 30-50% of pancreata with invasive carcinomas
Associated with usual ductal type adenocarcinoma
No association with colloid (mucinous) carcinoma
Margin involvement in cases with resected invasive carcinoma
PanIN 1 and 2 require no further therapy
PanIN 3
Older patient
No clear benefit as resection may deplete pancreatic reserves
Young patient
May benefit from additional resection to prevent progression to invasive carcinoma
Grading / Staging / Report
Grading
PanIN 1A
Flat
Tall columnar cells
Bland, basal nuclei
Abundant supranuclear mucin
PanIN 1B
Micropapillary architecture or
Basally stratified architecture
Otherwise identical to PanIN 1A
PanIN 2
Usually papillary but may be flat
Mild cytologic atypia
Loss of polarity
Nuclear crowding
Pseudostratification
Hyperchromasia
Mitotic figures rare, not atypical
No necrosis or cribriform architecture
PanIN 3
Architectural atypia
Cribriform or
Budding off of small clusters of cells into lumen
Lumenal necrosis
Significant cytologic atypia
Loss of nuclear polarity
Dystrophic (upside down) goblet cells
Prominent nucleoli
Frequent mitotic figures
Staging
Not relevant unless invasive carcinoma is present
Report
Grade
Presence or absence of invasive carcinoma
Lists
Mucinous Pancreatic Lesions
Bibliography
Hruban RH, Takaori K, Klimstra DS, Adsay NV, Albores-Saavedra J, Biankin AV, Biankin SA, Compton C, Fukushima N, Furukawa T, Goggins M, Kato Y, Kloppel G, Longnecker DS, Luttges J, Maitra A, Offerhaus GJ, Shimizu M, Yonezawa S. An illustrated consensus on the classification of pancreatic intraepithelial neoplasia and intraductal papillary mucinous neoplasms. Am J Surg Pathol. 2004 Aug;28(8):977-87.
Maitra A, Fukushima N, Takaori K, Hruban RH. Precursors to invasive pancreatic cancer. Adv Anat Pathol. 2005 Mar;12(2):81-91.
