What is MALT lymphoma

Lymphoma is divided into 2 broad groups: Hodgkin’s lymphoma and non-Hodgkin’s lymphoma. MALT lymphoma is a relatively uncommon type of non-Hodgkin’s lymphoma. It primarily affects the B lymphocytes.
Lymphoma means cancer of the lymphatic system. The lymphatic system is important to our immune system where it helps to combat infection. The lymphatic system consists of several organs, e.g. lymph nodes, spleen, thymus and bone marrow, where all these are connected by tiny vessels. Lymphatic fluid is the medium that circulates in these tiny vessels. Like blood, it has cells in them. These cells can be divided into 2 types: T cells and B cells.
MALT stands for Mucosa-Associated Lymphoid Tissue. This is lymphatic tissue that is found in other parts of the body such as the stomach, gut, lungs, eyes, and thyroid gland. Because of this, MALT lymphoma is an extranodal lymphoma, which means it happens outside the lymph nodes. The commonest site of MALT lymphoma is the stomach.

Statistics on MALT lymphoma

MALT lymphoma is on the increase in the world over the years. The following figures are according to the Australian Institute of Health and Welfare:

  • The incidence of non-Hodgkin’s lymphoma is increasing over the years.
  • In 2001, there were 3499 cases of non-Hodgkin’s lymphoma in Australia.
  • For non-Hodgkin’s lymphoma, the male:female ratio is 1.22:1.
  • In 2000, there were 2938 cases of B cell lymphoma (ie a subgroup of non-Hodgkin’s lymphoma affecting primarily B lymphocytes) in Australia. B cell lymphoma is the commonest subgroup of non-Hodgkin’s lymphoma.However, currently there is no figures onto the incidence of MALT lymphoma in Australia.

    Risk Factors for MALT lymphoma

    Age: MALT lymphoma affects mostly middle age to elderly population. However, cases have been recorded in children, adolescents and young adults.
    Sex: Slight female predisposition has been reported, but overall male:female ratio of non-Hodgkin’s lymphoma is 1.22:1 (see above)
    Approximately 70% of the gastric MALT lymphoma is associated with infection of the stomach by a bacteria called Helicobacter pylori.
    Some diseases are associated with MALT lymphoma, for example, dry eye/dry mouth, inflammation of the thyroid, inflammation of the liver and so on.

    Progression of MALT lymphoma

    Clinically and historically, non-Hodgkin’s lymphoma can be subdivided into 2 groups: indolent (low grade) and aggressive (high grade) lymphomas. MALT lymphoma is under the indolent group – which means it has better prognosis but may not respond to treatment when compared to aggressive groups of lymphomas.
    The course of the disease is dependent on the clinical stage when the MALT lymphoma is diagnosed.
    The staging can be summarised as below:

  • Stage I – involvement of a single lymph node region or organ or site other than lymph nodes
  • Stage II – 2 or more lymph node regions involved on the same side of diaphragm
  • Stage III – 2 or more lymph node regions involved on both sides of diaphragm
  • Stage IV – one or more organs (e.g. bone marrow) involvedEach stage is subclassified into A and B (e.g. IIA), where B means presence of B symptoms (see below) while A means abscence of the following symptoms:
  • Unexplained fever > 38 Centigrade
  • Unexplained weight loss (defined as >10% of body weight in 6 months)
  • Night sweatsBecause MALT lymphoma is also an extranodal lymphoma (see above in disease site), usually the alphabet E is added onto the staging (e.g. IE, IIE, IIIE). E means extranodal.

    How is MALT lymphoma Diagnosed?

    The usual basic MALT lymphoma tests will be done, including those to look at the blood and other blood components. Other general tests will determine the function of the liver.

    Prognosis of MALT lymphoma

    MALT lymphoma is considered an indolent non-Hodgkin’s lymphoma, hence it has better prognosis as compared to T cell lymphoma. Generally speaking, MALT lymphoma has a fairly good prognosis.
    The prognosis of MALT lymphoma is dependent on the clinical stage when the MALT lymphoma is diagnosed. The later the stage, the worse the prognosis.
    Other than staging, the following criteria are used to determine the prognosis of non-Hodgkin’s lymphoma.

  • Age >60
  • Serum lactate dehydrogenase (LDH) concentration greater than normal – this is a biochemical compound found in the blood
  • Patient is having symptoms and in bed <50% of the day or worse than this
  • Stage III or IV (see above for explanation on staging)
  • More than 1 involved site other than lymph nodesThe more the criteria are met, the worse the MALT lymphoma prognosis.

    How is MALT lymphoma Treated?

    With respect to MALT lymphoma treatment options, it is useful to divide MALT lymphoma into those affecting the stomach and those not affecting the stomach. The reason is that the management of these 2 groups are different.
    MALT lymphoma affecting the stomach is usually associated with Helicobacter pylori infection (a bacteria that infects the stomach – see ‘predisposing factors’. In this case multiple medications (usually 3) will be given for 1 week to treat the infection. Sometimes this can lead to remission of the lymphoma. Remission means that the lymphoma disappears and cannot be detected by available tests.
    Other wise, it is treated as MALT lymphoma not affecting the stomach.
    Generally MALT lymphoma not affecting the stomach can be treated with different types of treatment options depending on the clinical stage of the disease. The following are typically used, either alone or with combination:

  • Watchful monitoring: as MALT lymphoma is an indolent lymphoma, some grow very slowly and produce no symptoms for many years. Watchful monitoring may be the choice of therapy, but if the tumour starts to produce symptoms treatment can be given.
  • Chemotherapy: this is using anti-cancer drugs to kill the cancer cells. Usually only simple regimen is needed, but sometimes multiple drugs treatment may be needed.
  • Radiotherapy: this is using radiation to kill the cancer cells. If the disease does not involve many regions, radiation therapy can be considered.
  • Steroids: this is to reduce the side effects of anti-cancer drugs such as nausea and vomiting.
  • Surgery: if the disease is located in one region and can be taken out surgically, surgery can be used to remove part or whole of the particular organ.

    MALT lymphoma References

    [1] Cancer in Australia 2001 [online]. 2004. [Cited 2005 September 12th]. Available from: URL: http://www.aihw.gov.au/publications/can/ca01/ca01-c03.pdf
    [2] Clinical and pathologic features of the marginal zone lymphomas [online]. 2005. [Cited 2005 September 12th]. Available from: URL: http://uptodateonline.com/application/topic.asp?file=lymphoma/15507
    [3] How common is lymphoma [online]. 2003. [Cited 2005 September 12th]. Available from: URL: http://www.lymphoma.org.au/content/?id=25
    [4] Mucosa-Associated Lymphoid Tissue [online]. 2005. [Cited 2005 September 12th]. Available from: URL: http://www.emedicine.com/med/topic3204.htm