Splenic marginal zone lymphoma is generally an indolent lymphoma that involves the spleen, bone marrow and other organs. Splenomegaly is usually observed and when localized to the spleen then removal of the spleen often results in complete remission.
SMZL is also known as Splenic Lymphoma with Villous Lymphocytes. (villous means having the appearance of being covered with fine long hairs) It resembles hairy cell leukaemia and is considered to be the a leukaemic form of lymphoma. It is extremely rare and only accounts for about 1% of all lymphomas.
SMZL usually presents with massive splenomegaly, marrow and blood involvement. Patients often have anaemia and lymphocytosis. Overall the prognosis is very good for long term survival, with the median being approximately 13 years. The two most important risk factors are anaemia and lymphocytosis.
Previously a definitive diagnosis could only be made after removal of the spleen, but it has now been established that a conclusive diagnosis can be made from a bone marrow biopsy due to the peculiar intrasinusoidal BM involvement. (1)
There is no currently accepted International Prognostic Index for SMZL like there is for some other types of non-Hodgkin's lymphoma. Nevertheless there are recognized risk factors which may form the basis for an IPI in the future. There are three risk factors:
0 risk factors = Low risk, 88% 5 year cause specific survival (CSS)
1 risk factor = intermediate risk, 73% 5 year CSS
2 or more risk factors = high risk, 50% 5 year CSS
Splenic marginal zone lymphoma: a prognostic model for clinical use
Another contender for a valid international prognostic index uses Haemoglobin, platelet count, LDH and extrahilar lymphadenopathy to risk stratify patients. That study was published in August 2012. (4)
Historically splenectomy has been the preferred treatment of choice over chemotherapy. (5)Rituximab has changed this thinking. Due to its high efficacy and low toxicity it would seem to make the removal of the spleen unnecessary as an upfront treatment. Most people would probably rather keep their spleen if possible. Some research even suggests that Rituximab alone is superior to splenectomy alone and equal to Rituximab and chemotherapy. Rituximab and splenectomy obtains the highest complete remission rate but may not improve overall survival. (6)
Since losing the spleen is not very appealing to most people Rituxan monotherapy is likely to be the most beneficial option as a first line therapy. (7) (8) Splenectomy can always be used later if needed.
When chemotherapy stronger than just Rituxan monotherapy is required the purine analogues such as Fludarabine have been used with some success. Although Fludarabine is effective, it also has significant haematologic toxicity and is therefore often not recommended. (9) (10) (11) (12)
Other purine analogues such as Pentostatin (2-deoxycoformycin), 2-CDA (2-chlorodeoxyadenosine) appear to be showing promise. Though they have not taken the place of other treatments they may have a place in future treatments.
Risk stratification for Splenic Marginal Zone Lymphoma based on haemoglobin concentration, platelet count, high lactate dehydrogenase level and extrahilar lymphadenopathy: development and validation on 593 cases