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Lipomatous Lesions

The Digitized Atlas of Mouse Liver Lesions

Lipomatous Lesions (Ito Cell Tumors) - Click on thumbnails to view larger images

Lipomatous lesions (Ito cell tumors) are occasionally observed in mouse liver.  While they may often resemble lipomas, some portions of these lesions may have a myxomatous appearance.  They have been diagnosed as Ito cell lesions (Ito cell hyperplasia and Ito cell neoplasia) as well as lipomas.  One case in the NTP archives that is morphologically similar to an Ito cell neoplasm was diagnosed as a sinusoidal cell sarcoma.  The exact origin of these lesions is unknown but an origin from the vitamin A storing Ito cell is one possibility.  Since it is not possible to identify vitamin A storing cells in H&S-stained sections, it may be more prudent to refer to these cells simply as perisinusoidal lining cells.  The distinction between hyperplasia and neoplasia is not clear and the biological behavior of these lesions is not known.  Metastases have not been noted, suggesting that these are benign proliferative lesions.  These lesions are sometimes associated with extensive atrophy and destruction of hepatic parenchyma.
 
Dixon D, Yoshitomi K, Boorman GA, and Maronpot RR, 1994. “Lipomatous” Lesions of Unknown Cellular Origin in the Liver of B6C3F1 Mice. Vet.. Path. 31:173-182.
 
An Ito cell tumor that has replaced much of the normal hepatic parenchyma without distorting the normal contour of the liver; higher magnification shows fat-filled and stellate cells in the hepatic sinusoids.

Ito cell tumor
Ito cell tumor

 

 

The proliferating stellate cells have a myxomatous appearance in some areas and have caused atrophy of hepatic cords.
stellate cells
  
A relative discrete Ito cell tumor is present within this hepatic lobe; a higher magnification shows proliferation of stellate cells within the hepatic sinuosoidal spaces.
Ito cell tumor
Ito cell tumor
Ito cell tumor
This Ito cell tumor is comprised of a mixture of stellate cells and mature adipocytes. 
Ito cell tumor
  
 More examples of Ito cell proliferation in B6C3F1 mice.
 
Ito cell proliferation
 
Ito cell proliferation
 
Ito cell proliferation
 
Ito cell proliferation
 
Ito cell proliferation
 
Ito cell proliferation
 
Ito cell proliferation
 
Ito cell proliferation
 
Ito cell proliferation
 
Ito cell proliferation
 
Ito cell proliferation
 
Ito cell proliferation
 
Ito cell proliferation
 
Ito cell proliferation
 
Ito cell proliferation
 
Ito cell proliferation
  
 
Kupffer Cell Hyperplasia (Histiocytosis).  - Click on thumbnails to view larger images.  

Kupffer cell hyperplasia and hypertrophy is rarely seen in mice.  Hypertrophic Kupffer cells may contain pigment in some cases.

Examples of Kupffer cell hyperplasia.

 
kupffer cell hyperplasia
 
kupffer cell hyperplasia
 
kupffer cell hyperplasia
 
kupffer cell hyperplasia
  
 
Lymphoma (Malignant Lymphoma; Lymphosarcoma) - Click on thumbnails to view larger images.  

The liver is a relatively frequent site of infiltration by malignant lymphocytes, especially in strains with a high prevalence of lymphoma. 

Infiltration of malignant lymphocytes in a liver from an adult mouse.

 
malignant lymphocytes
 
malignant lymphocytes
 
malignant lymphocytes
 
malignant lymphocytes
  
Severe infiltration of the liver by malignant lymphocytes.  Hepatocytes visible in the lower right corner.
 
malignant lymphocytes
  
 
Mast Cell Tumor- Click on thumbnails to view larger images  

Mast cell tumor in the spleen and liver of a mouse.

 
Mast cell tumor
 
Mast cell tumor
 
Mast cell tumor
 
Mast cell tumor
  
 
Malignant Melanoma - Click on thumbnails to view larger images

Malignant melanoma metastatic to the liver is uncommon.  This case was from an adult C57BL/6 mouse.

 
malignant melanoma
 
malignant melanoma
 
malignant melanoma
 
malignant melanoma
 
malignant melanoma
 

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