Natural Killer T-Cell Lymphoma

In this view, the NK cell, bottom right, is attacking the cancer cell. In contrast, in NK-cell lymphoma, the natural killer is the cancer.

Lymphoma is a blood cancer that affects the lymphocytes, a kind of white blood cell.

The two main kinds of lymphoma are Hodgkin’s lymphoma, or HL, and non-Hodgkin’s lymphoma, or NHL.

Often, lymphomas are named based on a description of the normal cells that lead to cancer.

Normal cell types for lymphocytes include:

  • B cells
  • T cells
  • Natural killer cells, or NK cells

Each of these types has the potential to become cancerous.

However, most NHLs, about 90 percent, are of B-cell origin. Generally, much less is known about NK/T-cell malignancies than those of B-cell origin. NK-cell lymphoma is quite rare, which presents challenges to researchers who study this disease.

Natural Killer Cells

NK cells are cells that differentiate from something called the common lymphoid progenitor, which gives rise to both B and T cells. NK cells represent the third largest population of lymphocytes, following B and T cells. The name natural killer reflects the ability of NK cells to do important work for the immune system without requiring prior stimulation. They provide rapid responses to virus-infected cells and respond to tumor formation, without requiring activation to kill the infected cells. NK cells are known to differentiate and mature in the bone marrow, lymph nodes, spleen, tonsils and thymus.

Natural Killer T-Cell Lymphomas

NK cells share many features with T-cells.

Some tests do not distinguish between the two cell types. When NK cells become cancerous, the cancer is called NK or NK/T-cell lymphoma. The name NK/T-cell lymphoma reflects the fact that there may be uncertainty about which cells may have given rise to some of these lymphomas. A small number of "NK-cell lymphomas" appear to be derived from cytotoxic T-cells.

NK/T cell lymphomas are a mixed group of different diseases with varying clinical characteristics, prognoses and responses to treatment.

The current World Health Organization (WHO) Classification, 2008, describes two kinds of NK/T-cell lymphomas.

  • Nasal NK/T-Cell Lymphomas.Nasal NK/T-cell lymphoma is an aggressive lymphoma that is very rare in the United States. It is more common in Asia and parts of Latin America. For this reason, some researchers suspect that ethnicity may be involved in risk. Nasal NK/T-Cell lymphoma is associated with the Epstein-Barr virus and often involves the nasal area, windpipe, gastrointestinal tract, or skin. As this is an extremely rare malignancy, research is ongoing, and there is currently no standard treatment protocol.
  • Blastic “NK-cell” Lymphoma. According to the Lymphoma Research Foundation, blastic NK-cell Lymphoma is a very rare cancer that may affect only a few people each year. It was believed to arise from a T-cell or NK-cell. However, newer studies suggest another type of white blood cell -- a plasma cell or dendritic cell -- may give rise to the blastic NK-cell lymphoma. This is a fast-growing lymphoma that can be difficult to treat, according to the foundation. It can arise anywhere in the body. Dark red or purple skin lesions are a common feature.


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