Pancreatic intraepithelial neoplasia (PanIN) can be diagnosed and classified based on histologic features.


Criteria for malignancy: invasion of cells through the basement membrane


Histologic patterns of PanIN:

(1) flat

(2) basal pseudostratified

(3) micropapillary

(4) papillary


Features of PanIN-3:

(1) true cribriform pattern

(2) luminal necrosis

(3) budding off of small groups of cells into the lumen

(4) dystrophic goblet cells

(5) frequent mitoses

(6) abnormal and/or apical mitoses

(7) large, crowded nuclei with loss of polarity

(8) macronuceloli


Features of PanIN-1:

(1) none of the features for PanIN-3

(2) no or very rare mitoses

(3) small, round or oval nuclei with preserved nuclear polarity (perpendicular to the basement membrane) and little crowding

(4) abundant supranuclear mucin


If PanIN-1 shows a flat pattern, then it is termed PanIN-1A. Else (any other pattern) PanIN-1B.


Features of PanIN-2: features in between PanIN-1 and PanIN-3:

(1) rare to few mitoses, with nonapical (nonluminal) mitoses

(2) slight increase in nuclear size with or without crowding

(3) may show some loss in nuclear polarity


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