What characterizes chronic lymphocytic leukemia (CLL)?

• A. Rapidly progressing cancer of lymphoid precursors.
• B. Slowly progressive cancer of mature lymphocytes, most common in older adults.
• C. Malignancy of plasma cells in bone marrow.
• D. Malignancy of melanocytes in skin.

Answer: (B)

Chronic lymphocytic leukemia is a slowly progressive cancer of mature B lymphocytes, typically seen in older adults. This means the malignant cells look mature (not blasts or immature precursors) and accumulate over time, often giving a gradual rise in lymphocytes and signs like lymphadenopathy or splenomegaly rather than an abrupt, aggressive course. The disease is common in the elderly and may be found incidentally on routine blood tests.

This distinguishes it from other options: a rapidly progressing leukemia would involve immature lymphoid precursors and a quick, aggressive course. A malignancy of plasma cells describes multiple myeloma, which primarily affects the bone marrow and produces a different clinical picture. A malignancy of melanocytes describes melanoma, a skin cancer. The hallmark description here—slow progression and involvement of mature lymphocytes in older adults—is what characterizes chronic lymphocytic leukemia.