Page 131 - Concise Pathology for Exam Preparation ( PDFDrive )

116 SECTION I General Pathology

Staining Characteristics

• �Congo red
• �Ordinary light-pink or red colour
• �Polarized light-apple green birefringence (due to cross-b-pleated configuration)

• �Metachromatic stains (Rosaniline dyes): Examples are methyl violet and crystal violet.

Amyloid takes up a rose pink colour with these dyes.

• �Fluorescent stains of Thioflavin T and S: In ultraviolet light, amyloid fluoresces yellow.

• �Immunohistochemistry: Anti-AA and anti-lambda, anti-kappa antibodies can be used

to differentiate between different types of amyloid.

• �Toluidine blue: Blue colour in ordinary light and dark red, birefringence under polar-
ized microscopy.
• �Alcian blue: Blue-green colour.

• �PAS (periodic acid-Schiff) and H&E stains: Pink colour.

Histopathology
Kidneys (most common and most serious form of organ involvement)
Gross features
• �Kidneys are normal or enlarged in early stage and shrunken or contracted in late stage
(amyloid deposition causes vascular narrowing leading to shrinking of the organ)
Microscopic features
• �Primarily glomerular deposits
• �Subtle thickening of mesangial matrix due to mesangial deposits
• �Uneven widening of basement membrane of glomerular capillaries leading to capillary
narrowing due to basement membrane deposits
• �Distortion of glomerular vascular tuft due to confluent masses of or interlacing broad
ribbons of amyloid
Spleen
Gross features:
Moderate to marked splenomegaly
Microscopic features:
There are two patterns of deposition -
1.
Sago spleen: Deposits largely limited to splenic follicles; entire follicle replaced by
amyloid, leading to Tapioca-like granules
2.
Lardaceous spleen: Sparing of follicles; involvement of walls of splenic sinuses and con-
nective tissue framework of red pulp, leading to large map like areas
Liver
Gross features:
Moderate to marked hepatomegaly
Microscopic features (Flowchart 5.13):
Deposition starts in space of Disse
Amyloid deposits progressively encroached on adjacent parenchymal cells and sinusoids
Deformity, pressure atrophy, replacement of hepatocytes
Replacement of large areas of liver by amyloid

Vascular involvement and deposits in Kupffer cells
FLOWCHART 5.13. Evolution of morphological changes in hepatic amyloidosis.

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