What Is Biphenotypic Acute Leukemia (BAL)?

Biphenotypic leukemia is a mixed type of leukemia that originates in both lymphoid and myeloid cells. It typically has a poorer outlook than other acute leukemias. A stem cell transplant may improve your outlook but also has serious risks.

Biphenotypic acute leukemia (BAL) is an uncommon type of leukemia. Leukemia is cancer of the blood cells. BAL gets its name because it has features of two different types of leukemias. Biphenotypic means both types.

Most acute leukemias are classified as either myeloid or lymphoid:

• Lymphoid cells give rise to cells called lymphocytes. These are the white blood cells that help your body fight infections.
• Myeloid cells give rise to other types of white blood cells called granulocytes and monocytes.

If the origin of the leukemia is myeloid, it’s called acute myeloid leukemia (AML). If the origin of the leukemia is lymphoid, it’s called acute lymphoblastic leukemia (ALL). Acute means that the cancer grows quickly and needs treatment right away.

In rare cases, acute leukemia expresses both lymphoid and myeloid origin. BAL is a mixture of AML and ALL.

In 2008, the World Health Organization (WHO) revised its classification system for leukemia and introduced a new term called mixed-phenotype acute leukemia (MPAL), which includes BAL.

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BAL is more difficult to treat than other types of leukemia due to its mixed qualities. The outlook is usually poor compared with AML or ALL .

Leukemia happens when stem cells in your blood undergo genetic changes that make them grow out of control. Like other types of leukemias, the cause of BAL is likely a combination of genetic and environmental factors , but the exact cause isn’t completely understood.

BAL can occur at any age but is more common in adults over age 60. BAL is slightly more common in people assigned male at birth. The incidence is similar across races and ethnicities.

How common is biphenotypic acute leukemia?

BAL isn’t common. According to 2023 data from the American Cancer Society, leukemia (all kinds) makes up just 3% to 4% of cancer diagnoses. Only 1% to 5% of all acute leukemias are BAL. Scientists estimate there are just 0.35 cases per 1 million people per year.