Acute leukemia is a disease arising from bone marrow. In principle, leukemic blasts can be found all over the body. The most common places where metastases can be found outside the bone marrow are spinal fluid (CNS leukemia), liver, spleen, lymph nodes, and testicles.
When the lymph nodes in the mediastinum are involved (occurs primarily in T cell leukemia), tumors can potentially compress the airways.
In acute myelogenous leukemia, there can rarely be extramedullary tumors (myelosarcoma) with or without detectable bone marrow involvement. These patients are treated as AML.