Lymphomas of the gastro-intestinal tract - pathophysiology, pathology, and differential diagnosis.

The gastrointestinal tract (GIT) is the most commonly involved site of extranodal lymphomas. The close association between chronic inflammation and specific GIT lymphomas not only provide interesting insights into the pathobiology of lymphomas but also poses unique diagnostic challenges. A clear understanding of marginal zone and mucosa associated lymphoid tissue (MALT) in health and disease is helpful to place GIT lymphomas in proper context. A wide variety of lymphomas besides MALT lymphomas occur in various parts of the GIT. The characteristic pathological, immunophenotypic, and genetic features of different GIT lymphomas categorized according to World Health Organization (WHO) classification are presented. The epidemiological, clinical, and pathological features of lymphomas occurring in each part of the GIT are summarized and the key points regarding lymphomas at each site are emphasized. A tabular summary of the important differential diagnostic considerations at each site is given and suggestions for a minimal diagnostic work up are provided.