A clinical case of B-cell lymphoma in a Japanese Black cow with monoclonal proliferation of B-cells as revealed by polymerase chain reaction based on the immunoglobulin light chain gene.

A 35-month-old Japanese Black cow was presented to a local veterinarian with a main complaint of premature labor. There was no swelling of lymph nodes on the body surface and no palpable mass on rectal examination. Although atypical lymphocytes were observed in the peripheral blood, no lymphocytosis was recorded. On Day 12, the cow developed hindlimb paresis and was euthanized. Necropsy revealed swelling of some lymph nodes, and white nodules in uterus and right atrial appendage. Histopathological examination revealed B-cell lymphoma. In clonality analysis of peripheral blood and tumor tissue, monoclonal proliferation was detected by PCR for immunoglobulin light chain (IgL) λ, suggesting neoplastic proliferation of B-cell. IgL-PCR is thought to be a possible tool for diagnosis of B-cell lymphoma.