Acute lymphocytic leukemia (ALL)

Leukemia is a blood cancer of the bone marrow, which is the organ responsible for blood cell development. Normally, there are three types of cells in your blood stream:

• White blood cells
• Red blood cells
• Platelets

Acute leukemia is considered lymphoid or myeloid based on the type of blood cell that is involved. Lymphoid cells are cells that, under normal development, would have become lymphocytes, which are types of white blood cells. Myeloid cells are cells that would have become other blood cells (white blood cells other than lymphocytes, red blood cells or platelets) under normal development. In patients with acute leukemia, immature cells called "blasts" overtake the bone marrow. In patients with acute lymphocytic leukemia (ALL), the bone marrow is overtaken by lymphoid blasts.

ALL is the most common type of childhood cancer, but it is more common in adults than children. There are approximately 3,000 to 5,000 new cases of ALL per year in the United States. Once diagnosed, a person will ALL will need to receive treatment as soon as possible. If left untreated, the disease progresses rapidly and can be fatal.

ALL may also be referred to as acute lymphoblastic leukemia or acute lymphoid leukemia.

Acute lymphocytic leukemia (ALL) can be characterized into different sub-types:

• Philadelphia chromosome-positive ALL
• Philadelphia chromosome-negative ALL
• B cell ALL
• T cell ALL

B cell ALL is more common than T cell ALL. Other names and sub-types of B cell and T cell ALL include:

• Acute B-lymphocytic leukemia
• Acute precursor B cell leukemia
• Pre-B cell lymphocytic leukemia
• Acute T-lymphoblastic leukemia

Your individual treatment plan will depend on your ALL sub-type.

The Philadelphia chromosome

Some people with ALL have a genetic abnormality referred to as the Philadelphia chromosome. If you have the Philadelphia chromosome, you will receive chemotherapy and targeted therapies designed specifically for you and the genetic makeup of your leukemia. The Philadelphia chromosome, discovered more than 50 years ago at Penn, provided the first evidence that genetic abnormalities were linked to cancer. The discovery ushered in the modern period of cytogenetics in the understanding of leukemia. Now, the Center for Personalized Diagnostics builds on this legacy and is set to pave the way for precision medicine.