Electron-microscopic examination of primary diffuse tracheobronchial amyloidosis. Role of fibroblasts in amyloid formation

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

AIMS

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.

METHODS AND RESULTS

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.

CONCLUSIONS

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.

Localized oral amyloidosis: ultrastructural and immunohistochemical study

An histopathological, ultrastructural and immunohistochemical study of localized amyloidosis in the floor of mouth of a 58-year-old male in good health is reported. The lesion was composed of nodular deposits of amyloid surrounded by fibroblastic or histiocytic cells, and metaplastic ossification was seen in some deposits. Ultrastructural findings disclosed typical amyloid fibrils with felt-like structure. Closely connected with the amyloid deposits were cells with active histiocytic or fibroblastic appearance. Their cytoplasm contained amyloid fibrils. At the outermost area of the amyloid deposits, bundles of amyloid fibrils projected from these cells into amyloid deposits. Amyloid protein of the present case did not react to any antisera using anti-AA, anti-A lambda, anti-A kappa and anti-prealbumin antisera. It can be assumed that histiocytes or fibroblasts play an important role in local amyloid formation, however, the nature of amyloid fibril protein in the present case is unknown.