**7. Conclusion**

Amyloidosis is characterized morphologically by amorphous deposition of amyloid within tissue. The deposition is caused by aggregation of misfolded protein. Any disruptive processes in protein homeostasis (proteinostasis) can cause such misfolding and aggregation. Although different species of amyloid protein have different organotropisms and physiochemical properties, they appear remarkably similar when deposited within the target tissue. Clinical signs and symptoms of different types are largely affected by the organ where the amyloid is deposited. However, different treatment modalities and clinical courses according to the type mandate the exact subtyping of amyloid.

The confirmation and subtyping of amyloidosis heavily depend on pathologic examination of abdominal fat, minor salivary gland, or target organs. The gold standard for confirmation of amyloidosis is Congophilia and birefringence. Additional modalities such as IHC, EM, and MS can help further subclassify the type of amyloidosis.

Lately, new types of amyloidosis have been identified by MS. Atypical structure of amyloid continues to be found in various organs. Contrary to the conventional definition of amyloid, such as extracellular amorphous deposition, intracellular and spherical structure amyloids have been discovered. In addition, novel mutations of the same protein have been shown to confer totally different clinical implications.

#### *Amyloid Diseases*

The accumulation of new histologic findings and molecular studies will be an important key to understanding the disease mechanisms and, further on, the treatment of amyloid-associated diseases.
