Lymphoid leukemia

Classification

Historically, they have been most commonly divided by the stage of maturation at which the clonal (neoplastic) lymphoid population stopped maturing:

• Acute lymphoblastic leukemia
• Chronic lymphocytic leukemia

However, the influential WHO Classification (published in 2001) emphasized a greater emphasis on cell lineage. To this end, lymphoid leukemias can also be divided by the type of cells affected:

• B-cell leukemia
• T-cell leukemia
• NK-cell leukemia

The most common type of lymphoid leukemia is B-cell chronic lymphocytic leukemia.

B-cell leukemias

B-cell leukemia describes several different types of lymphoid leukemia which affect B cells.

Other types include (with ICD-O code):

• 9826/3 – Acute lymphoblastic leukemia, mature B-cell type
• 9833/3 – B-cell prolymphocytic leukemia
• 9940/3 – Hairy cell leukemia

T-cell leukemias

T-cell leukemia describes several different types of lymphoid leukemias which affect T cells.

The most common T-cell leukemia is precursor T-cell lymphoblastic leukemia. It causes 15% of acute leukemias in childhood, and also 40% of lymphomas in childhood. It is most common in adolescent males. Its morphology is identical to that of precursor B-cell lymphoblastic leukemia. Cell markers include TdT, CD2, CD7. It often presents as a mediastinal mass because of involvement of the thymus. It is highly associated with NOTCH1 mutations.

Other types include:

• Large granular lymphocytic leukemia
• Adult T-cell leukemia/lymphoma
• T-cell prolymphocytic leukemia

In practice, it can be hard to distinguish T-cell leukemia from T-cell lymphoma, and they are often grouped together.

NK cell leukemia

Aggressive NK-cell leukemia (ANKL) is a lymphoid leukemia that is a deficiency NK cells. Not very much is known about this disease due to its rarity, but it is highly aggressive. A majority of patients with NK cell leukemia die within a year of diagnosis, and for ANKL in particular, half of patients die within two months.

Diagnosis

The requirements for diagnosing ANKL are as follows:

1. Immature-looking NK cells
2. Certain immunophenotypes
3. Germline configuration genes: TCR-β and IgH
4. Restricted cytotoxicity

The T-cell receptor (TCR) is an important factor when ANKL is being diagnosed along with T-cell leukemia. The TCR gene transcripts are normally positive for ANKL. Current Research is attempting to find the causation of ANKL. So far, the researchers have concluded that lineage of the T-cell receptor gene does not predict the behavior of the disease.

Treatment

ANKL is treated similarly to most B-cell lymphomas. Anthracycline-containing chemotherapy regimens are commonly offered as the initial therapy. Some patients may receive a stem cell transplant.

Overall survival depends on the stage of the cancer when treatment is initiated, and on a composite of numerous risk factors. The median time from diagnosis to death is less than 1 year in patients overall. Patients diagnosed early and/or with fewer risk factors can sometimes enter complete remission and expect much longer survival.