Which type of leukemia is characterized by disease cells in peripheral circulation?

Chronic lymphocytic leukemia (CLL) is characterized by the presence of abnormal lymphocytes in the peripheral circulation. In CLL, these cancerous cells accumulate in the blood, bone marrow, and lymphoid tissues, leading to elevated lymphocyte counts detectable in blood tests. This is a hallmark feature of the disease, distinguishing it from other types of leukemia where the cancerous cells may not be as prominently found circulating in the blood.

For instance, while acute myeloid leukemia and acute lymphoblastic leukemia can also present with abnormal cells in circulation, they generally involve a more aggressive clinical course and different cell types as opposed to the indolent, often asymptomatic nature of CLL. Small lymphocytic lymphoma is closely related to CLL and primarily presents in lymphoid tissues, where the malignant cells may not be as abundant in the bloodstream.

Thus, CLL is specifically defined by the accumulation of these neoplastic lymphocytes within the peripheral blood, making it the correct answer to the question regarding which type of leukemia is characterized by such a finding.