Unlike other cancers, acute lymphocytic leukemia (ALL) does not have a traditional staging system. Because it is a blood cancer, ALL is found throughout the body and does not usually form tumors like most other cancers. The outlook for a person with ALL and the appropriate treatment regimen depends on other types of information including:

The Type of Lymphocytes Affected

The classification of ALL is primarily based on the type of lymphocytes that are affected - B cells or T cells.

• B-cell ALL is more common and can be further divided into several subtypes, including:
  • B-cell ALL with hypodiploidy (the leukemia cells have fewer than 44 chromosomes [normal cells have 46])
  • B-cell ALL with hyperdiploidy (the leukemia cells have more than 50 chromosomes)
  • B-cell ALL with a translocation between chromosomes 9 and 22 [t(9;22)] (the Philadelphia chromosome, which creates the BCR-ABL1 fusion gene)
  • B-cell ALL with a translocation between chromosome 11 and another chromosome
  • B-cell ALL with a translocation between chromosomes 12 and 21 [t(12;21)]
  • B-cell ALL with a translocation between chromosomes 1 and 19 [t(1;19]
  • B-cell ALL with a translocation between chromosomes 5 and 14 [t(5;14)]
  • B-cell ALL with amplification (too many copies) of a portion of chromosome 21 (iAMP21)
  • B-cell ALL with translocations involving certain tyrosine kinases or cytokine receptors (also known as “BCR-ABL1–like ALL”)
  • B-cell ALL, not otherwise specified
• T-cell ALL is less common and can also be divided into different subtypes based on the maturity of the cells. T-cell ALL is more frequent in young adults and in men.

The Patient's Age at Diagnosis

The age of the patient at diagnosis is another important factor in the classification of ALL. The disease is often categorized as either pediatric or adult ALL, with different treatment approaches and prognoses. Pediatric ALL generally has a better prognosis than adult ALL.

The Initial White Blood Cell Count at Diagnosis

People with lower white blood cell counts (less than 30,000 for B-cell ALL and less than 100,000 for T-cell ALL) when they are first diagnosed tend to have a better prognosis.

Certain Genetic Features of the ALL Cells

Certain genetic characteristics are also used to classify ALL. There are around 25 different genetic subtypes of ALL. One of the most common subtypes is Philadelphia-positive ALL which occurs in 1 in 4 patients with ALL. The presence of the Philadelphia chromosome can affect the prognosis and treatment of the disease. Generally, having this genetic feature has resulted in a poorer prognosis for people with ALL, but with the development of targeted therapy drugs called tyrosine kinase inhibitors (TKIs), outcomes have improved. Additional genetic abnormalities that tend to have poorer outcomes include:

• A translocation between chromosomes 4 and 11
• A translocation involving chromosome 14
• Amplification (too many copies) of part of chromosome 21
• Fewer than 44 chromosomes (hypodiploidy)
• 5 or more chromosome changes (complex karyotype)

Genetic abnormalities that tend to have better outcomes include:

• A translocation between chromosomes 12 and 21
• More than 50 chromosomes (hyperdiploidy)

What are the Phases of Acute Lymphocytic Leukemia?

In addition to these classifications, the disease is often described based on its phase. There are three phases: remission, relapse, and refractory.

• Remission is when there are no signs of the disease after treatment
• Relapse is when the disease returns after a period of remission
• Refractory ALL is when the leukemia cells do not respond to treatment

In summary, the staging and classification of ALL is complex and involves multiple factors. It is crucial in determining the appropriate treatment strategy and predicting the patient's prognosis.

Want to Learn More About Acute Lymphocytic Leukemia?

Keep reading HealthTree for ALL's 101 pages!

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