|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.
|The proliferating stellate cells have a myxomatous appearance in some areas and have caused atrophy of hepatic cords.|
|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.|
|This Ito cell tumor is comprised of a mixture of stellate cells and mature adipocytes.|
|More examples of Ito cell proliferation in B6C3F1 mice.|
|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.
|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.
|Severe infiltration of the liver by malignant lymphocytes. Hepatocytes visible in the lower right corner.|
|Mast Cell Tumor- Click on thumbnails to view larger images|
Mast cell tumor in the spleen and liver of a mouse.
|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.