What is a common site for metastasis in acute lymphoblastic leukemia?

In acute lymphoblastic leukemia (ALL), a common site for metastasis is the central nervous system (CNS). This is particularly important because leukemia is a hematologic malignancy that can have a propensity to infiltrate the CNS. The lymphoblasts, which are immature white blood cells, can cross the blood-brain barrier and lead to central nervous system involvement.

The CNS is a critical area of concern in ALL because it is associated with complications such as leukemia-related neurological symptoms, increased risk of infection, and treatment challenges. This is why CNS prophylaxis, which includes intrathecal chemotherapy, is often part of the treatment regimen for patients with ALL to prevent CNS involvement from the outset.

While bone marrow is indeed involved and can be a major site of disease activity in ALL, the question specifically addresses metastasis, and the CNS is recognized as a distinct site where leukemia cells may infiltrate beyond the primary sites like the bone marrow or peripheral blood. The liver and kidneys can be affected by leukemic infiltration as well, but the CNS remains a particularly notable site.