Histological and proteomic characterization of musculoskeletal amyloidomas.

Introduction: The term amyloidoma applies to localized deposits of amyloid in the absence of systemic amyloidosis. Skeletal and soft tissue amyloidomas are very rare and the pathogenesis is usually associated with lymphoproliferative disorders (plasmacytomas or plasmacytoid lymphomas) or as a consequence of local chronic inflammation.

Methods: In this paper we report the histological and immunohistochemical features of four cases of musculoskeletal amyloidoma in association with combined laser capture microdissection (LCM) of Congo Red positive regions with a recent microproteomics workflow that improves the sensitivity of the analysis in order to confirm the nature of the protein deposit.

Results: Proteomic techniques allowed to elucidate the nature of the amyloid protein deposit, improving the results obtained by immunohistochemistry (IHC). IHC results were confirmed in two cases while LCM coupled with bottom-up microproteomics was necessary to type the other two cases, for which IHC was inconclusive.

Conclusions: In conclusion, proteomic techniques were thus confirmed as a fundamental tool for the complete investigation of protein deposits.