Characterization of amyloid deposits in exocrine pancreatic tumors in cats.

Some types of amyloidosis are observed as localized conditions associated with tumors, such as plasmacytoma and C-cell carcinoma. Although pancreatic endocrine tumors have been linked to amyloid deposition, the potential for amyloid formation in exocrine pancreatic tumors has remained unexplored in both animals and humans. We examined amyloid deposits in 24 feline cases of exocrine pancreatic tumors. Histologic analysis identified amyloid deposits in 8 cases, appearing as Congo red-positive amorphous material in the luminal corpora amylacea. Microdissection and mass spectrometry analysis of amyloid deposits from 5 cases identified lithostathine as the major component in 3 of the cases. Immunohistochemistry confirmed the presence of lithostathine in these deposits, identifying lithostathine-derived amyloid. Conversely, other cases had no consistent lithostathine positivity, indicating that multiple amyloidogenic proteins, not just lithostathine, may be involved in exocrine pancreatic tumor-associated amyloidosis.