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Amyloidosis
Amyloid deposits are congophilic and show “apple green” birefringence under polarized light
Birefringence is best demonstrated by turning light to maximum and pulling color filters out
• Immunohistochemistry
P glycoprotein: Present in all cases, can help in diagnosis
Light chains, SAA, and LECT2: Helps in further classification
Ancillary Tests
• Electron microscopy
Central electron-lucent core and nonbranching fibrils of indefinite length with mean diameter of 10 nm
• Laser microdissection and mass spectrometry
Most accurate method for identification of amyloid subtype
Paraffin-embedded tissue or cytology material can be used
Top Differential Diagnoses
• Monoclonal immunoglobulin deposit disease
Vessel Wall AmyloidDeposits are seen in the hepatic arteriole and portal vein in the vascular pattern of hepatic amyloidosis. This distribution is characteristic, but not specific, for the AA form.
Congo Red StainCongo red stain highlights the vascular distribution of amyloid deposits in the hepatic arteriole and portal vein .
Sinusoidal AmyloidCongo red stain highlights the diffuse sinusoidal pattern of hepatic amyloidosis. The amyloid deposits are compressing the hepatocytes , leading to hepatic plate atrophy.
Globular AmyloidAmyloid deposits stain with trichrome stain, but it is often a paler staining than that seen with collagen .
TERMINOLOGY
Definitions
• Heterogeneous disease characterized by deposition of glycoprotein fibrils in extracellular matrix and vessel walls
Deposits composed of low molecular weight subunits (5-25 KDa) derived from normal serum proteins
• Liver involvement may be seen in different types
Primary, or AL, amyloidosis
– Deposits are composed of fragments of monoclonal light chains
– Occurs alone or associated with other hematologic diseases (plasmacytoma, multiple myeloma Waldenstrom macroglobulinemia)
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