Papillary mucinous adenoma arising in adenomyomatous hyperplasia of the gall bladder.

A case of papillary mucinous adenoma arising in adenomyomatous hyperplasia (AMH) of the gall bladder is reported. The lesion was unsuspected and discovered by routine palpation of the gall bladder during laparotomy. The adenoma developed within fundal AMH and showed cytological atypia. This case illustrates that neoplastic proliferation is indeed possible in AMH and challenges the classical opinion that AMH is devoid of neoplastic potential.