Non-Hodgkin’s lymphoma (NHL) is a heterogeneous group of lymphomas originating from various types of lymphocytes, including B-cells, T-cells, and natural killer (NK) cells.
- B-cells, or B lymphocytes, make proteins called antibodies to protect you from infections in response to antigens. Antigens are markers that enable the immune system to identify substances in the body, including harmful ones such as bacteria and viruses.
- T-cells, called T lymphocytes, help the immune system fight germs and destroy harmful pathogens like viruses, bacteria, and parasites. These cells start in the bone marrow, mature in the thymus, and relocate to the lymph tissue or bloodstream.
- Natural killer cells destroy infected and diseased cells like cancer cells in the early stages, preventing their spread. Unlike other lymphocytes, they are called “natural” killers due to their ability to destroy potential threats without prior exposure to a particular pathogen.
Non-Hodgkin’s lymphoma can occur at any age and affect lymph nodes and other lymphatic tissues such as the spleen, bone marrow, and digestive tract.
There are many subtypes of non-Hodgkin’s lymphoma, each with unique characteristics, growth patterns, and treatment approaches. Some subtypes are indolent (slow-growing), while others are more aggressive.
According to World Health Organisation (WHO), non-Hodgkin lymphoma is divided into over 60 subcategories. B-cell lymphomas account for up to 85% of all non-Hodgkin’s lymphoma cases. The several subtypes of B-cell lymphoma include:
- Diffuse Large B-Cell Lymphoma (DLBCL): DLBCL is the most common subtype of non-Hodgkin lymphoma, comprising 30 to 40% of all cases. It usually presents as rapidly growing tumours and can arise in various lymphoid tissues. DLBCL can occur at any age and is characterised by large, abnormal B-cells.
- Follicular Lymphoma (FL): FL is a slow-growing subtype of non-Hodgkin lymphoma that arises from abnormal B-cells. It is often indolent, meaning it progresses slowly over time.FL is characterised by abnormal lymphoid follicles (small masses of tissues containing aggregations of inflammatory cells) in the lymph nodes and bone marrow. It typically affects older adults and can be associated with certain genetic abnormalities.
- Mantle Cell Lymphoma (MCL): MCL is a relatively rare subtype (only about 5% cases) of non-Hodgkin lymphoma, primarily affecting middle-aged and older individuals. It arises from abnormal B-cells in the lymph nodes' mantle zone (the dark outer rim of the follicle). MCL is known for its aggressive behaviour and tends to spread to other organs, such as the bone marrow and gastrointestinal tract.
- Burkitt Lymphoma (BL): Burkitt lymphoma is a highly aggressive subtype of non-Hodgkin lymphoma, primarily affecting children and young adults. BL is characterised by rapidly growing tumours and can involve multiple organs, including the lymph nodes, bone marrow, and central nervous system.
It is associated with genetic abnormalities involving the MYC gene. MYC genes are a family of proteins that involves several cell functions, such as cell growth, maturation, and death. Genetic changes in the DNA sequence of MYC genes can result in cancer cells growing and spreading in the body.
- Primary Mediastinal B-cell Lymphoma (PMBCL): It is a rare subtype of B-cell lymphoma (2-3% of all NHL cases) that originates from abnormal B-cells in the mediastinum (space in the chest that holds the heart and other important structures). It primarily affects women in their 20s and 30s and is characterised by large B-cells resembling thymic B-cells.
- Small Lymphocytic Lymphoma (SLL): SLL is a low-grade subtype of non-Hodgkin lymphoma characterised by the proliferation of small mature lymphocytes. Most of the cancer cells are typically located in the lymph nodes. It is closely related to chronic lymphocytic leukaemia (CLL) and shares similar clinical and genetic features.
- Marginal Zone Lymphoma (MZL): MZL is a group of indolent lymphomas that arise from B-cells in the marginal zone of the lymphoid tissues. It can occur in different organs, including the lymph nodes, spleen, and gastrointestinal tract. MZL is further categorised into three subtypes based on where the lymphoma forms:
- Extranodal MZL of mucosa-associated lymphoid tissue or MALT lymphoma (lining of the belly, skin, lungs, thyroid, bowels, salivary gland, or near the eye)
- Nodal MZL (lymph nodes or bone marrow)
- Splenic MZL (spleen, blood, and bone marrow)
Apart from the B-cells, non-Hodgkin’s lymphoma can also develop in the abnormal T-cells. Though less common than B-cell lymphomas, T-cell lymphomas tend to be more aggressive and involve various organs, including the lymph nodes, skin, and internal organs. Subtypes include:
- Peripheral T-cell Lymphoma (PTCL): This is a diverse group of aggressive T-cell lymphomas that arise from mature T-cells and can affect various organs.
- Anaplastic Large Cell Lymphoma (ALCL): ALCL is characterised by large, abnormal T-cells and can occur in the lymph nodes, skin, or other organs. It is further classified into ALK-positive and ALK-negative subtypes.
- Cutaneous T-cell Lymphoma (CTCL): CTCL primarily affects the skin and includes subtypes like mycosis fungoides (a rare kind of skin cancer that affects the body’s T-cells) and Sézary syndrome (a rare but aggressive form of lymphoma that affects the skin, blood, and lymph nodes).
- Adult T-cell Leukaemia/Lymphoma (ATLL): ATLL is caused by human T-cell lymphotropic virus type 1 (HTLV-1) infection and is mainly found in regions where the virus is endemic. HTLV-1 is a common virus that infects your T-cells.
- Extranodal NK/T-cell Lymphoma, Nasal Type: This subtype primarily affects the nasal cavity and upper respiratory tract and is associated with Epstein-Barr virus (EBV) infection.
The specific subtype of non-Hodgkin’s lymphoma, along with factors like the disease stage, the patient’s overall health, and other individual factors, guides the treatment plan.
Treatments for non-Hodgkin’s lymphoma may include chemotherapy, radiation therapy, immunotherapy, targeted therapies, or stem cell transplantation, depending on the specific characteristics of the lymphoma and the patient’s circumstances.