Lymphoma (historically lymphosarcoma was used for diffuse forms of the disease) is a malignancy arising from lymphocytes or lymphoblasts. Lymphoma can be restricted to the lymphatic system or can arise as extranodal disease. This, along with variable aggressiveness results in a diverse imaging appearance.
Lymphoma accounts for ~4% of all cancers . They are more common in developed countries.
In children, lymphoma accounts for 10-15% of all cancers, being the third most common form of malignancy .
Lymphoma can present as nodal or extranodal disease. Hodgkin lymphoma and low-grade non-Hodgkin lymphoma (NHL) classically present as nodal disease, whereas high-grade NHL can present with complications from mass effect such as superior vena cava obstruction, cauda equina syndrome, etc. Extranodal disease can affect any organ.
Lymphomas are a malignancy that arise from mature lymphocytes. The etiology is unknown but potential lymphomatogenic risk factors include :
- viral infection, e.g. EBV, HTLV-1, HIV, HCV, HSV
- bacterial infection, e.g. Helicobacter pylori
- chronic immunosuppression, e.g. post-transplantation
- prior chemotherapy (especially alkalising agents) and drug therapy, e.g. digoxin
Lymphomas are currently classified according to the 2008 WHO classification of tumors of hematopoietic and lymphoid tissues. The main division is into:
- Hodgkin lymphoma (Hodgkin disease) (40%)
- non-Hodgkin lymphoma (60%)
- mature B-cell lymphoma
- mature T-cell and NK-cell lymphoma
- post-transplant lymphoproliferative disorders
The majority (85%) of lymphomas are B-cell with the remainder (15%) being T-cell .
Additionally, it is worth, especially for radiologists, dividing extranodal lymphomas according to the location:
- central nervous system (CNS)
- head and neck lymphoma
- thoracic lymphoma
- gastrointestinal lymphoma
- hepatobiliary lymphoma
- musculoskeletal lymphoma
- cutaneous lymphoma
- genitourinary lymphoma
Imaging characteristics will depend on the location and subtype of lymphoma. CT is the workhorse of imaging in lymphoma and plays a crucial role in staging (see main article: lymphoma staging). US and MRI are also used; for example, when assessing cervical lymph nodes (US) or CNS lymphoma (MRI). FDG-PET is used for staging and re-staging of lymphoma.
Treatment and prognosis
Lymphoma cure rates are comparatively high (up to 90%) compared to many other malignancies. Prognosis depends not only on histological subtype and grade but also on stage, hence why imaging plays a pivotal role in treatment. Aggressive lymphomas (e.g. Burkitt lymphoma) typically have a prognosis of weeks without treatment.