Microcystic adenoma of the pancreas (glycogen-rich cystadenoma) with stromal amyloid deposits

We report a case of a pancreatic glycogen-rich microcystic serous adenoma with stromal amyloid deposits, focusing on the significance of isolated amyloid deposits in tumours. The architectural pattern was characterized by thin-walled cysts lined by a single layer of flat or cuboidal epithelial cells intensely stained by the PAS-reaction only before diastase digestion, suggesting the presence of glycogen. Tumour stroma was composed of broad fibrocollagenous tissue with lamellar hyalinized areas which were positively stained by Congo red and showed green birefringence and dichroism with polarized light. For amyloid protein characterization, immunohistochemical studies were performed with anti-beta amyloid protein and anti-amyloid precursor pre-A4695. The former antibody diffusely stained tumour stroma, while the latter stained only scattered stroma cells. This is the first documented case of amyloid deposition in pancreatic serous adenoma. We indicate that the source of amyloid is an APP-like precursor secreted by stromal myofibroblasts.