**4.4 Spleen**

The spleen is mostly affected by AL type with plasmacytoid lymphovascular proliferation. The spleen shows two distinct gross patterns which are sago spleen and lardaceous spleen. Sago spleen has a gray, waxy, nodular appearance and is mild to moderately enlarged, and histologically, white pulp (follicles) is affected.

**67**

**4.5 Brain**

**Figure 4.**

**Figure 3.**

*Pathologic Findings of Amyloidosis: Recent Advances DOI: http://dx.doi.org/10.5772/intechopen.84268*

If amyloid deposits grow, they replace the white pulp. Lardaceous spleen shows a diffuse waxy appearance and moderate to marked enlargement. Histologically,

The most common amyloid we see in the brain is β-amyloid. β-amyloid accumulates diffusely in the extracellular space of the cerebral cortex and is most commonly related to Alzheimer's disease. Characteristically, we can appreciate numerous extracellular depositions of amyloid plaques within the cortex (**Figure 5**). Amyloid plaques show filamentous appearance and can be demonstrated with a Congo red and a silver stain and β-amyloid IHC. Some dense amyloid plaques are surrounded by dystrophic neurites, reactive astrocytes, and microglia. Additionally, β-amyloid

amyloid deposition is seen within the splenic sinuses and blood vessels.

*Sinusoidal deposition of amyloid in liver, Congo red stain under Texas red filter.*

*Sinusoidal depositions of homogeneously bright pink material in liver, H&E stain.*

*Pathologic Findings of Amyloidosis: Recent Advances DOI: http://dx.doi.org/10.5772/intechopen.84268*

*Amyloid Diseases*

**66**

**4.4 Spleen**

**Figure 2.**

**Figure 1.**

**4.3 Liver**

*Mesangium deposition of amyloid in kidney, ALλ type in immunofluorescence.*

*Mesangium depositions of homogeneously bright pink material in kidney, H&E stain.*

The most common amyloid type in the liver is AL and leukocyte-derived chemotaxin 2 (LECT2) type [7]. LECT 2 type amyloid (ALECT2) deposition was relatively recently found within the kidney and first reported in 2008 [8]. LECT 2 is synthesized in the liver and is a chemotaxin that attracts neutrophils. Grossly, appearance ranges from normal to moderate and massive hepatomegaly. Histologically, we can see bright pink amorphous deposition within the sinusoidal space and vessel in the portal tract. AL type tends to have a sinusoidal pattern and a vascular pattern in the portal tract, but AA type shows a vascular pattern within the portal tract [9] (**Figures 3** and **4**). A globular pattern in sinusoids has been reported in LECT 2 hepatic amyloidosis [10]. Even if there are more specific patterns depending on the type, they are not accurate, and sometimes there are overlapping patterns. Thus, confirmation with a specific stain is important. Kupffer cells and Multinucleated giant cells can be seen near the amyloid deposition. If amyloid expands, it induces hepatocyte atrophy and replaces normal hepatic tissue, causing liver failure.

The spleen is mostly affected by AL type with plasmacytoid lymphovascular proliferation. The spleen shows two distinct gross patterns which are sago spleen and lardaceous spleen. Sago spleen has a gray, waxy, nodular appearance and is mild to moderately enlarged, and histologically, white pulp (follicles) is affected.

**Figure 3.** *Sinusoidal depositions of homogeneously bright pink material in liver, H&E stain.*

**Figure 4.** *Sinusoidal deposition of amyloid in liver, Congo red stain under Texas red filter.*

If amyloid deposits grow, they replace the white pulp. Lardaceous spleen shows a diffuse waxy appearance and moderate to marked enlargement. Histologically, amyloid deposition is seen within the splenic sinuses and blood vessels.

#### **4.5 Brain**

The most common amyloid we see in the brain is β-amyloid. β-amyloid accumulates diffusely in the extracellular space of the cerebral cortex and is most commonly related to Alzheimer's disease. Characteristically, we can appreciate numerous extracellular depositions of amyloid plaques within the cortex (**Figure 5**). Amyloid plaques show filamentous appearance and can be demonstrated with a Congo red and a silver stain and β-amyloid IHC. Some dense amyloid plaques are surrounded by dystrophic neurites, reactive astrocytes, and microglia. Additionally, β-amyloid

**Figure 5.** *Amyloid plaque seen in Alzheimer disease, β amyloid antibody in IHC.*

can deposit within small-to-medium-sized arteries in the superficial cortex and leptomeningeal space and causes cerebral amyloid angiopathy. Cerebral amyloid angiopathy causes recurrent lobar hemorrhage. Furthermore, most Alzheimer'saffected brains show cerebral amyloid angiopathy as well.
