Papillary fronds form in the gallbladder mucosa.
The papillae are lined by columnar epithelial cells without atypia.
Papillary hyperplasia of the gallbladder is most often seen secondary to chronic irritation, and seen in association with cholecystitis, cholelithiasis and cholesterolosis. For example, in 1323 cholecystectomy specimens, papillary hyperplasia was found 376 (38.4%) of patients and cholesterolosis was found in 206 (15.6%) of patients. There is an association between the two entities and it is theorized that papillary hyperplasia is an adaption of the mucosa to allow increased absorption of cholesterol from the lumen into the capillaries (Celoris).
Primary papillary hyperplasia, on the other hand, is not associated with a background of chronic cholecystitis, cholelithiasis or cholesterolosis. It is a poorly defined entity with a handful of case reports in the literature (Stringer).
Papillary hyperplasia consists of papillary fronds lined by columnar calls. The epithelium does not exhibit atypia -- in contrast to biliary papillomatosis which exhibits cytologic atypia and carries a definite risk of malignant transformation (Stringer, Rosai).
Celoria GC, Rodríguez Otero JC, Proske SA et al. Papillary hyperplasia and cholesterolosis of the gallbladder. Medicina (B Aires). 1994;54(1):31-4.
Stringer MD, Abbott C, Arthur RJ et al. Primary papillary hyperplasia of the gallbladder: a rare cause of biliary colic. J Pediatr Surg. 2001 Oct;36(10):1584-6.
Rosai, J. Rosai and Ackerman's Surgical Pathology. 9th Ed. Philadelphia, PA: Elsevier; 2004: 1044.