How a Diagnosis of T Cell or NK Cell Leukemia/Lymphoma is Made: General Overview of PTCL Diagnosis

By: Lorinda Soma, M.D.

Assistant Professor

Associate Director, Hematopathology Laboratory

University of Washington

General Overview of How a Diagnosis of T Cell or NK Cell Leukemia / Lymphoma is Made.

In order to make a diagnosis of T cell leukemia or lymphoma or NK cell leukemia or lymphoma, a sample of your blood, bone marrow or organ tissue will need to be obtained so it can be examined by a hematopathologist (doctor who specializes in the diagnosis of leukemias and lymphomas).  The process starts with obtaining the sample (either by a blood draw or biopsy procedure) and then getting that sample to the laboratory for evaluation by the hematopathologist.  Once in the laboratory, the sample may be evaluated under the microscope to get a closer look at the cells, by a machine called a flow cytometer to see what kinds of proteins are on the cells, and by using different methods to look at the chromosome, genes or DNA in the cells.  What types of testing are done in the laboratory depends on the type of sample and what type of cancer is present.  The amount of time needed to process the sample and do all the needed tests to come to the best answer/diagnosis will vary.  When all the testing is done, the information is evaluated together and the diagnosis is made.  The hematopathologist renders a diagnosis based on all the laboratory data, and the hematologist-oncologist correlates this information with the patient’s clinical and radiographic imaging studies to determine what the laboratory diagnosis means for the particular patient and how it should be approached and treated.

What Sample is Needed to Make a Diagnosis of T Cell Lymphoma and How is it Obtained?

First, lets talk about the samples (blood, bone marrow, tissue) and how they are obtained.

Blood

A blood sample can be taken from a peripheral arm vein (this can be done during a routine blood draw for other laboratory tests).  Peripheral blood contains red blood cells, white blood cells, and platelets that are bathed and transported around your body in a fluid called plasma.  The T cells and NK cells are also part of the lymphocyte population, which makes up a component of your white blood cells.

• White blood cell: White blood cells (WBC’s) are present in blood, which helps to move them around your body.  WBC’s help fight against infections, and also help destroy cancerous cells.  There are several different types of white cells, but the three most common WBC’s in the peripheral blood are neutrophils, monocytes and lymphocytes.  Infections and abnormal/cancer cells are identified by the lymphocytes, and removed or destroyed by the neutrophils and monocytes, as well as some T cells and NK cells.  T cells and NK cells belong in the lymphocyte category.

• Red blood cell: A cell that carries oxygen to the organs/tissue.

• Platelet: A particle in the blood that helps with clotting

Bone Marrow

Bone marrow is the somewhat fluid component of your bone.  The marrow is composed of support tissue, which provides structure/scaffolding and nourishment for the hematopoietic cells (white blood cells, red blood cells and platelet producing cells) to grow.  A bone marrow sample may consist of both a biopsy (bone and bone marrow) and aspirate (bone marrow only), and is performed by a physician, physician assistant or nurse who has been trained to perform this procedure.  Usually in an adult, the biopsy is taken from the iliac crest (hip bone), although sometimes an alternative site, such as the sternum, may be biopsied.

Tissue

Various organs/tissues can be primarily or secondarily involved by lymphoma.  In T cell and NK cell lymphomas, lymph nodes, skin, nasal cavity  / sinus, liver, spleen and the intestine are some of the more common tissue sites to be involved.  The involved tissue / organ will become enlarged or develop a mass due to the growing, abnormal lymphoma population.  Depending on the site, tissues may be biopsied in the clinic, through a radiographic procedure or in the operating room.  The biopsy may be a needle core biopsy (usually performed by radiology, where a sliver of tissue about the size of pencil lead is obtained by a mechanical device using CT or ultrasound to guide the procedure) or excisional biopsy (the entire lymph node or large portion of the mass is removed for evaluation).