Chapter 9b LYMPHOMA

Chapter 9b LYMPHOMA

1. DEFINITION

Lymphomas may be defined as solid malignancies of the lymphoid tissue. They are an important cause of morbidity and mortality, constituting the fifth most frequent cause of death from cancer in the U.S. They are subdivided into Hodgkins disease and Non Hodgkins Lymphoma (NHL).

Hodgkins disease rarely affects the GI tract and will not be further considered. NHL most frequently effects and presents as a nodal problem with or without gastrointestinal involvement. We are concerned here with that minority that present with the main effect in the GI with or without local node involvement. The ICD 10AM Codes are C82 and C83.

It is not proposed to canvass the complex immunobiology of NHL. It suffices to say that NHL represents a malignant transformation of a B or T cell or rarely, another related cell in its journey from marrow or thymus to its peripheral site of activity. In the gut lymphoid tissue is called Mucosa Associated Lymphoid Tissue (MALT). Should malignant change occur then it is termed MALT lymphoma and is generally of B cell lineage.

Lymphomas may occur in any part of the gut from mouth to rectum with major geographic variations. In the west, gastric lymphoma is the usual type whereas in the Middle East the small gut is usual. There are many variation, both in site and in cell of origin; their determination may be a complex problem with implications for therapy.

It is proposed to discuss briefly several of the more frequent situations.

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2. GASTRIC LYMPHOMA

Gastric marginal zone B cell lymphoma of MALT type. This arises from B cells in MALT which is not normally present in the stomach but MALT tissue may appear in the stomach in response to chronic infection with H.pylori. This is generally a low grade lymphoma which usually resolves on H.pylori eradication but it may be non responsive and more aggressive.

Geographically it shows major variation according to the prevalence of H.pylori colonization and the risk is calculated at 1:30000 to 1:80000 with an onset at about 60 years of age with an equal sex incidence. Almost all patients with gastric lymphoma have evidence of past or present H.pylori colonization. As the antrum is the most often affected part of the stomach, so the atrum is the usual site of gastric lymphoma but it may occur anywhere in the form of ulcer, erosive changes or erythema.

3. DIFFUSE LARGE B CELL LYMPHOMA OF STOMACH

This constitutes nearly half of gastric lymphomas. It does not have the same clear evidence of association with H.pylori but it may be a Hp related lymphoma that goes on to a high grader malignancy and dedifferentiates.

4. SMALL BOWEL LYMPHOMA

There are a variety of these based upon their different immunological characteristics. They may be of B or T cell origin. Among the larger recognised types are:

• Mediterranean Lymphoma. This is limited to the area around the Mediterranean and certain other parts such as Africa, South America and India. It occurs in young adults living in conditions of poverty and poor hygiene and sanitation. It may represent a response by MALT tissue to long standing antigenic stimulation of the gut but the situation is obscure.

• Enteropathy Associated Intestinal T Cell Lymphoma. This is a

complication of Coeliac disease (Celiac Sprue in the U.S.) caused by

malignant T cell transformation. It used to be regarded as a frequent

complication of that disorder but it is now clear that in most wheat

dependant societies, Coeliac disease is not uncommon and lymphoma

is in fact a rare complication.

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References

1. Collins R: Gastrointestinal lymphomas, including immunoproliferative small intestinal disease : in Feldman M, Friedman LS, Sleisenger MH, eds. Sleisenger and Fordtran’s Gastrointestinal and Liver Disease. 7

Ed. (Saunders, Philadelphia, 2002), Vol .1, p.

450.