Lymphoma is a cancer that begins in lymphocytes, white blood cells essential to the immune system. Although these abnormal cells typically accumulate in the lymphatic system, they can also affect organs like the spleen. Splenic lymphoma is a rare, slow-growing non-Hodgkin lymphoma primarily involving the spleen, peripheral blood, and bone marrow. Located beneath the rib cage on the left side of the abdomen, the spleen functions as a large blood filter. Infiltration by lymphoma cells disrupts this function, leading to enlargement.
Specific Types of Splenic Lymphoma
The most frequent classification is Splenic Marginal Zone Lymphoma (SMZL), a low-grade B-cell lymphoproliferative disorder. This type originates from B-lymphocytes located in the marginal zone at the edge of the spleen’s white pulp. SMZL accounts for less than 2% of all non-Hodgkin lymphoma cases. The abnormal B-cells in SMZL often display distinctive projections, known as villous lymphocytes, which can sometimes be seen circulating in the blood.
Other B-cell malignancies prominently involving the spleen include Hairy Cell Leukemia (HCL) and Splenic Diffuse Red Pulp Small B-cell Lymphoma (SDRPL). HCL involves B-cells with an unusual “hairy” appearance that typically infiltrate the bone marrow, blood, and spleen. SDRPL is a distinct classification characterized by the accumulation of small B-lymphocytes mainly within the red pulp of the spleen. Precise classification is important because while these conditions share splenic involvement and B-cell origin, they differ in microscopic features, cellular markers, and overall behavior, guiding management.
Recognizing the Signs and Symptoms
Splenic lymphoma, particularly the SMZL subtype, often has an indolent course and may be discovered incidentally during routine exams or blood tests. When symptoms appear, they can be vague and non-specific. The most common physical finding is splenomegaly, or enlargement of the spleen.
This enlarged spleen can cause discomfort in the upper left abdomen or back. A frequent complaint is early satiety, the feeling of being full after eating only a small amount of food, which occurs when the expanded spleen pushes against the stomach. Systemic effects can also manifest as “B symptoms,” including unexplained fevers, drenching night sweats, and unintentional weight loss.
The disease’s invasion of the bone marrow and the enlarged spleen’s increased activity can lead to cytopenias (low blood cell counts). Anemia (shortage of red blood cells) causes persistent fatigue and shortness of breath. Thrombocytopenia (low platelet counts) can result in increased bruising or bleeding.
Diagnostic Procedures and Staging
The diagnostic process begins with a physical examination to assess for splenomegaly and lymph node swelling. Blood work starts with a Complete Blood Count (CBC) to check for cytopenias. The peripheral blood smear is also examined for abnormal circulating lymphocytes, particularly the villous lymphocytes associated with SMZL.
Flow cytometry is performed on the blood sample to analyze markers on the surface of the abnormal B-cells, helping distinguish SMZL from similar lymphomas. Imaging studies, such as a CT scan of the chest, abdomen, and pelvis, measure the spleen’s size and check for involvement in lymph nodes or other organs.
The definitive diagnosis often requires a bone marrow aspiration and biopsy, typically taken from the hip bone. This procedure determines the degree of bone marrow infiltration, a common finding in SMZL. The biopsy sample is analyzed to identify the distinctive intrasinusoidal pattern of infiltration, a microscopic feature that helps confirm the diagnosis. Additional blood tests include screening for the Hepatitis C virus, as chronic infection has been associated with SMZL development.
The Ann Arbor staging system is frequently used to classify the extent of the disease, though it has limitations for splenic lymphomas because bone marrow involvement is common. This system classifies the disease from Stage I (one lymph node region or organ involved) to Stage IV (widespread involvement of non-lymphatic organs). Staging information, combined with immunophenotyping and genetic analysis, informs the overall prognosis and treatment strategy.
Treatment Strategies and Outlook
For many asymptomatic patients or those with minimal disease burden, the initial approach is “watch and wait” or active surveillance. This strategy involves regular monitoring with physical exams, blood tests, and imaging, reserving intervention until the disease progresses or symptoms develop. Because SMZL is typically a slow-growing lymphoma, the risks associated with immediate treatment may outweigh the benefits.
When treatment becomes necessary due to significant splenomegaly, cytopenias, or B symptoms, several effective options are available. Splenectomy (surgical removal of the spleen) has historically been a common treatment, rapidly correcting cytopenias and relieving discomfort. However, splenectomy is now less frequently utilized as a first-line treatment due to the success of newer drug therapies and potential surgical complications.
Targeted therapy with the monoclonal antibody Rituximab is a highly effective modern treatment. Rituximab targets the CD20 protein on the surface of lymphoma B-cells, leading to their destruction, and is often used alone or combined with chemotherapy. Chemotherapy regimens, such as bendamustine and Rituximab (BR), are utilized for more advanced or symptomatic disease. If the disease is linked to a chronic Hepatitis C infection, treating the virus with antiviral therapy can sometimes lead to the regression of the lymphoma itself.
The general outlook for SMZL is favorable, characterized by an indolent course with a median survival extending beyond ten years for most patients. The goal of treatment is typically to manage symptoms and achieve durable remission rather than a complete cure. While a subset of cases may transform into a more aggressive type of lymphoma, the majority of patients can expect to live for many years with effective disease management.