Final answer:
The most sensitive marker for diagnosing hairy cell leukemia is CD-103, which helps distinguish this form of chronic leukemia characterized by aberrant B cells from other B cell disorders.
Step-by-step explanation:
Hairy cell leukemia is a rare type of chronic leukemia that is characterized by the proliferation of abnormal B cells. These cells appear 'hairy' under the microscope due to their irregular cytoplasmic processes. Among the diagnostic markers used to identify hairy cell leukemia, the most sensitive is CD-103. This is a cell surface protein that is highly specific for hairy cell leukemia and helps distinguish it from other B cell disorders.
Other markers that may be associated with hairy cell leukemia include CD19, CD20, and CD22. While leukocytosis refers to excessive leukocyte proliferation, leukopenia describes a below-normal production of leukocytes. Lymphocytes, particularly B cells, which are part of the lymphoid stem cell line, play a crucial role in specific immunity and can become neoplastic, as in hairy cell leukemia.