20 research outputs found
Malignant Lymphoma with Severe Infiltrative Growth into Skeletal Muscles in WBN/Kob Rats
Although spontaneously occurring neoplasms have been reported repeatedly in F344, SD and
Wistar rats, which are commonly used strains for routine toxicologic and carcinogenicity
studies, there are only a few reports of malignant lymphoma or lymphatic leukemia except
for large granular lymphocytic leukemia (LGL) in F344 rats. Malignant lymphoma
(lymphosarcoma) is thought to be uncommon in F344 rats. The authors encountered malignant
lymphomas of the non-LGL leukemia type with characteristic pathologic features in WBN/Kob
rats. The mean age at onset of the disease in all 13 affected rats (8 males and 5 females)
was about 60 weeks. Common and characteristic clinical signs were abnormal gait with hind
limb paralysis. Macroscopically, the enlargement of the lymph nodes, spleen and liver was
slight to moderate. Scattered multiple white-to-gray nodules encompassed the aorta and
assumed a bead-like appearance near the thoracic and lumbar vertebrae.
Histopathologically, neoplastic proliferative changes were predominant in the bone marrow
tissue of the entire body, and many tumor cells infiltrated the spleen and several lymph
nodes. The most striking histological features were constant and severe infiltration of
tumor cells in the adipose tissue and skeletal muscle adjacent the thoracic and lumber
vertebrae. Immunohistochemically, all tumor cells were positive for B-cell markers (PAX-5,
CD79a and CD45) and negative for CD3. From the results of immunohistochemistry and
morphological examination, these tumors were diagnosed as malignant B-cell lymphomas