Extranodal NK/T cell lymphoma

by Jason Wasserman MD PhD FRCPC
September 11, 2023

What is extranodal NK/T cell lymphoma?

Extranodal NK/T cell lymphoma is a type of cancer that starts from cells in the immune system, specifically natural killer (NK) cells and T cells.

What type of lymphoma is extranodal NK/T cell lymphoma?

Extranodal NK/T cell lymphoma is a type of non-Hodgkins lymphoma (NHL).

What does extranodal mean?

Extranodal means that the tumour started outside of a lymph node. This is different from most types of lymphomas which start inside a lymph node.

What are the symptoms of extranodal NK/T cell lymphoma?

The symptoms of NK/T cell lymphoma depend on the location of the tumour. Tumours in the nasal cavity can lead to symptoms such as nasal blockage, discharge, and bleeding. Tumours involving one of the paranasal sinuses can lead to symptoms such as facial pain, swelling, sinus infections, and visual changes. Tumours in the nasopharynx, oropharynx, and larynx can lead to symptoms such as difficulty breathing and voice changes.

What causes extranodal NK/T cell lymphoma?

Extranodal NK/T cell lymphoma is strongly associated with Epstein-Barr virus (EBV). However, most people infected with EBV will not go on to develop this type of cancer. Because extranodal NK/T cell lymphoma is much more common among particular ethnic groups, genetic factors also appear to play a role in the development of this disease.

What does it mean if the tumour is described as nasal type?

Extranodal NK/T cell lymphoma is described as nasal type when the tumour starts in the midline of the head and neck, specifically the nasal cavity, oropharynx, nasopharynx, or larynx.

What does it mean if the tumour is described as non-nasal type?

Extranodal NK/T cell lymphoma is described as non-nasal (or extranasal) type when the tumour starts in a part of the body outside of the midline of the head and neck. Common non-nasal sites include the skin, gastrointestinal tract, and testis.

How is this diagnosis made?

The diagnosis of extranodal NK/T cell lymphoma can be made after a biopsy is performed and tissue is examined under a microscope by a pathologist.

What does extranodal NK/T cell lymphoma look like under a microscope?

When examined under the microscope, the tumour is made up of variably sized abnormal-looking lymphoid cells (immune cells), specifically NK cells and T cells. Pathologists often describe these cells as atypical which means they look different from normal, healthy immune cells. The nucleus (the part of the cell that holds the genetic material) is often convoluted or folded. The tumour cells may surround blood vessels in a pattern that pathologists describe as angiocentric. Large areas of necrosis (cell death) are commonly seen.

What other tests may be performed to confirm the diagnosis?

Additional tests including immunohistochemistry (IHC) and in situ hybridization (ISH) are commonly performed to confirm the diagnosis of extranodal NK/T cell lymphoma.

Immunohistochemistry

Immunohistochemistry (IHC) allows pathologists to identify the types of cells in the tumour. When this test is performed, the tumour cells are typically positive for T cell and NK cell markers such as CD3, CD56, and TIA1. Tumours made up predominantly of T cells may also be positive for CD2, CD5, and CD8. Some tumours will be positive for CD30. The tumour cells will be negative for B cell and plasma cell markers including CD20, CD79, and CD138.

In situ hybridization

In situ hybridization (ISH) for EBER is commonly performed to see if the tumour cells have been infected with Epstein-Barr virus (EBV). EBER is a piece of genetic material made by the virus once it is inside the cell. Cells that have been infected will be described as positive for EBER while those that are not infected will be described as negative for EBER.