Lymphoma is a type of blood cancer that occurs when B or T lymphocytes, the white blood cells that form a part of the immune system and help protect the body from infection and disease, divide faster than normal cells or live longer than they are supposed to. Lymphoma may develop in the lymph nodes, spleen, bone marrow, blood or other organs and eventually they form a tumor.
Typically, lymphoma presents as a solid tumor of lymphoid cells. Treatment might involve chemotherapy and in some cases radiotherapy and/or bone marrow transplantation, and lymphomas can be curable depending on the histology, type, and stage of the disease. These malignant cells often originate in lymph nodes, presenting as an enlargement of the node (a tumor). It can also affect other organs in which case it is referred to as extranodal lymphoma. Extranodal sites include the tonsils, skin, brain, bowels and bone. Lymphomas are closely related to lymphoid leukemias, which also originate in lymphocytes but typically involve only circulating blood and the bone marrow (where blood cells are generated in a process termed haematopoiesis) and do not usually form static tumors. There are many types of lymphomas, and in turn, lymphomas are a part of the broad group of diseases called hematological neoplasms.
Lymphoma presents with certain non-specific symptoms. If symptoms are persistent, lymphoma needs to be excluded medically.
Lymphoma is definitively diagnosed by a lymph node biopsy, meaning a partial or total excision of a lymph node that is then examined under the microscope. This examination reveals histopathological features that may indicate lymphoma. After lymphoma is diagnosed, a variety of tests may be carried out to look for specific features characteristic of different types of lymphoma. These include:
Several classification systems have existed for lymphoma. These systems use histological findings and other findings to divide lymphoma into different categories. The classification of lymphoma can affect treatment and prognosis. Classification systems generally classify lymphoma according to:
Hodgkin lymphoma is one of the best-known types of lymphoma, and differs from other forms of lymphoma in its prognosis and several pathological characteristics. A division into Hodgkin and non-Hodgkin lymphomas is used in several formal classification systems. A Hodgkin lymphoma is marked by the presence of a type of cell called the Reed-Sternberg cell.
The current accepted definition is the WHO classification, published in 2001 and updated in 2008, is the latest classification of lymphoma and is based upon the foundations laid within the “Revised European-American Lymphoma classification” (REAL). This system attempts to group lymphomas by cell type (i.e. the normal cell type that most resembles the tumor) and defining phenotypic, molecular or cytogenetic characteristics. There are three large groups: the B cell, T cell, and natural killer cell tumors. Other less common groups, are also recognized. Hodgkin lymphoma, although considered separately within the World Health Organization (and preceding) classifications, is now recognized as being a tumor of, albeit markedly abnormal, lymphocytes of mature B cell lineage.
Prognosis and treatment is different for HL and between all the different forms of NHL, and also depends on the grade of tumour, referring to how quickly a cancer replicates. Paradoxically, high-grade lymphomas are more readily treated and have better prognoses . A well-known example of a high-grade tumour is that of Burkitt’s lymphoma, which is a high-grade tumour that has been known to double within days, but is readily treated.
Many low-grade lymphomas remain indolent for many years. In these lymphomas, metastases are very likely. For this reason, treatment of the non-symptomatic patient is often avoided. In these forms of lymphoma , watchful waiting is often the initial course of action. This is carried out because the harms and risks of treatment outweigh the benefits. If a low-grade lymphoma is becoming symptomatic, radiotherapy or chemotherapy are the treatments of choice; although they do not cure the lymphoma, they can alleviate the symptoms, particularly painful lymphadenopathy. Patients with these types of lymphoma can live near-normal lifespans, but the disease is incurable.
Treatment of some other, more aggressive, forms of lymphoma can result in a cure in the majority of cases, but the prognosis for patients with a poor response to therapy is worse. Treatment for these types of lymphoma typically consists of aggressive chemotherapy, including the CHOP or R-CHOP regimen.
Hodgkin lymphoma typically is treated with radiotherapy alone, as long as it is localized. Advanced Hodgkin disease requires systemic chemotherapy, sometimes combined with radiotherapy. Chemotherapy used includes the ABVD regimen.