Gastrointestinal lymphomas in a North American population: clinicopathologic features from one major Central-Midwestern United States tertiary care medical center.

Background: Gastrointestinal (GI) lymphomas are very common types of extranodal lymphomas, and we hypothesize there are regional differences in subtype, distribution in the GI tract, and epidemiological features among the different populations. Methods: We retrospectively evaluated the clinical, molecular and histologic features of North American primary and secondary GI lymphomas diagnosed from 2000-2009 seen at our institution. We utilized immunohistochemistry and fluorescence in situ hybridization to further evaluate a subset of the gastric lymphomas. Results: Extranodal marginal zone lymphomas of mucosal associated lymphoid tissue (MALTs) and diffuse large B cell lymphomas (DLBCLs) were the most common subtypes of GI lymphomas. Select gastric DLBCLs (N= 6) and MALTs (N= 13) were further examined for API2-MALT1 and IGH translocations, and P16 and P53 protein expression. Gastric MALTs showed frequent API2-MALT1 (38%) but not IGH translocations (0%), and the DLBCLs showed neither translocation. Expression of P16 and P53 proteins and the proliferative index were compared between high grade gastric lymphomas (gastric DLBCLs) and low grade gastric lymphomas (gastric MALTs). P53 overexpression (P= 0.008) and a high proliferation index [Ki-67] (P= 0.00042) were significantly associated with gastric DLBCL, but no statistically significant difference was observed in P16 expression (p= 0.108) between gastric DLBCL and gastric MALT. Conclusion: Our study revealed that GI lymphomas from a Central-Midwestern North American population showed differences and similarities to non-North American cohorts. In addition, API2-MALT1, P16 and P53 abnormalities occurred frequently in gastric lymphomas from this North American population. [ABSTRACT FROM AUTHOR]