Well-Differentiated Lymphocytic Leukemia in a Dog: Long-Term Survival Without Therapy

Abstract. Well-differentiated lymphocytic leukemia was found during routine hematologic examination of a 12-year-old female poodle with signs of anxiousness, panting and pica. The total white blood cell count was 106,9OO/pl and at least 90 % of the leukocytes were small, normal-appearing lymphocytes. The dog was examined several times during a 23-month period before it was killed at the owner’s request for conditions unrelated to the leukemia. The hematologic picture of the leukemia was essentially unchanged during this time. A deep nuclear cleft was seen in most lymphocytes examined by electron microscopy. Cell surface markers showed most blood lymphocytes to be B-cells. These cells responded poorly to mitogen stimulation. The term lymphocytic leukemia, in its broad usage, refers to the presence of neoplastic lymphocytes in the peripheral circulation. In human medicine this term generally is limited to lymphoproliferative disease that originates in the bone marrow. Terms such as lymphoma or lymphosarcoma are used for lymphoproliferative diseases originating in lymphoid tissues other than bone marrow [25, 361. In man, lymphocytic leukemia is classified into two types. The well-differentiated type i