If an individual is suspected to have Non-Hodgkin’s lymphoma investigations are required to establish the diagnosis and stage the disease, which in turn helps in selecting an appropriate treatment option. Following are some commonly used investigations for Non-Hodgkin’s lymphoma:
1.Lymph Node Biopsy: This is the test which can confirm the diagnosis of NHL. Thus, patients presented with NHL symptoms are generally suggested to have a biopsy of involved lymph node(s). Whole node excision biopsy is recommended.
Excisional biopsy: In this technique, the affected lymph node is removed surgically.
The collected biopsy sample is then tested in a laboratory and can help in establishing the diagnosis of NHL based on the appearance and distribution of cells in the biopsy sample. Further testing by immunohistochemistry helps in confirming the diagnosis.
2.Laboratory Test for Biopsy Samples: The collected biopsy sample is then tested in a laboratory that helps in establishing the diagnosis of NHL based on the presence of characteristic NHL cells in the biopsy sample. The biopsy samples can also provide other useful information about the NHL cells such as the severity of cancerous changes involved and the presence of specific surface proteins (when examined using Immunophenotypic analysis).
Following are various techniques used for collecting this information:
-Immunohistochemistry: In this technique, a very thin portion of the biopsy sample is first attached to a microscope glass slide. The sample is then treated with a specific antibody which gets attached to a protein specific to certain types of cancer cells. Some reagents are then added to the treated sample that causes the bound antibody to changes its color. The change in color of the antibody-protein complex can be observed under the microscope, which confirms the type of cancer cells.
-Flow cytometry: In this technique, the biopsy sample is first treated with some fluorescent antibodies that get attached to certain specific proteins (antigens) on the surface of cells. The treated sample is then analyzed using a laser beam and a detector attached to a computer. This test can detect different types of cells in the sample along with the quantification of each type of cells.
-Cytogenetic Testing: In this technique, chromosomes are evaluated for certain defects which are common in NHL. The sample cells are first grown in the culture medium and are observed under a microscope after adding certain reagents that bind only to a specific defective portion of a chromosome. This test enables detection of chromosomal abnormalities like translocation, amplification, or deletion.
-Fluorescent in situ hybridization (FISH): In this technique, a fluorescent RNA probe is used which binds to a specific portion of a chromosome in the sample cells. Then, the sample can be examined under a microscope to determine the presence of certain chromosomal abnormalities like translocation, addition, or deletion. This technique is very sensitive, fast, and accurate. Thus, it is preferably used for detecting specific chromosomal abnormalities.
-Polymerase chain reaction (PCR): This is a very sensitive diagnostic tool which can detect a very small number of lymphoma cells with a specific genetic change (different types of NHL generally possess different genetic change, as described in overview section). Thus, identification of a genetic modification can establish the diagnosis of the specific type of NHL.
-Bone Marrow Aspiration/Biopsy: It is routinely employed in a case of NHL. But with the advent of PET-CT, bone marrow aspiration/biopsy may not be required in some cases. It helps to detect the involvement of bone by lymphoma and hence, stage the disease.
3.Imaging Tests: : These tests help to detect the involvement of lymph nodes, liver, spleen, bones, etc by lymphoma and play an important role in defining the extent of disease. Alternatively, these tests are employed after treatment to evaluate the treatment efficacy and to detect any signs of disease progression/recurrence.
-Positron emission tomography (PET) scan: This technique uses a radioactive substance (fluorodeoxyglucose [FDG], etc) that is given via intravenous injection prior to the procedure. Cancer cells absorb larger amounts of the radioactive substance than normal cells. The areas of higher radioactivity indicate cancerous tissue on the PET scan. This technique is considered sensitive to stage certain subtypes of NHL (that are FDG avid) and to assess response to treatment. It can also detect any bone lesion that may indicate bone involvement. It can also be combined with CT scan (PET/CT) to accurately diagnose the extent of disease in distant body parts.
-Computed tomography (CT) scan: In this technique, detailed cross-sectional images of body organs are generated using x-rays with or without contrast agents. It can be utilized for scanning neck, chest, abdomen and pelvis for the diagnosis of any abnormal lymph node or involvement of liver, spleen, or other extranodal structures. It can also be used to guide a biopsy needle to collect biopsy samples. Also, it can be used for determining the extent of disease and for planning the treatment in case radiation therapy is indicated for the treatment.
-Magnetic resonance imaging (MRI) scan: This technique provides detailed images of internal body structures using radio waves, strong magnetic field, and gadolinium-based contrast material (which is used via intravenous injection to improve the clarity of the MRI images). It can be used when it is suspected that the disease has spread to the brain or spinal cord.
Apart from above investigational tests, few other techniques may also be employed in some special cases. For example, endoscopic evaluation of the upper gastrointestinal tract is usually employed to confirm the presence of H. pylori infection in gastric MALT lymphoma. A full thickness skin-biopsy is generally indicated in the case of NHL that involves the skin, for example, cutaneous T-cell lymphomas (CTCLs).
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