Primary gastrointestinal B-cell lymphoma - A clinicopathological and immunohistochemical study of 61 cases with an evaluation of prognostic parameters

We hereby present a retrospective clinicopathological and immunohistochemic al study of surgically resected primary gastrointestinal (GI) lymphoma with an analysis of parameters of potential prognostic relevance. From a larger series of 144 cases of primary GI lymphomas, we chose 61 cases with suffic ient clinical follow-up (mean 60, range 1-219 months), classified either as extranodal marginal zone B-cell lymphoma of MALT type (MALT lymphoma) or d iffuse large B-cell lymphoma (DLBCL), after having excluded other subtypes. In addition to conventional clinical and morphological parameters, the exp ression levels of Ki-67 (MIB-1), bcl-2 and p53 were evaluated for prognosti c significance. Twenty-one (34.4%) cases were classified as pure low grade marginal zone B-cell lymphoma of MALT type, 12 (19.7%) cases as low grade M ALT lymphoma with a high grade component (mixed type), and 28 (45.9%) cases as primary extranodal DLBCL. Most of the lymphomas (53/61; 86.9%) were loc alized in the stomach, 3 (4.9%) in the small bowel, 3 (4.9%) multifocal in both stomach and small intestine and 2 (3.3%) in the large bowel. MIB-1 exp ression in more than 30% of tumor cells was detected in 42 (68.6%), bcl-2 e xpression in 20 (32.8%) and p53 accumulation in more than 10% of neoplastic cells in 16 (26.2%) lymphomas. Both high Ki-67 expression and p53 accumula tion were more prevalent in the DLBCL. 30 (49%) patients showed lymph node involvement at surgery, 14 (23%) patients suffered tumor recurrence, and 24 (38.5%) died during the follow-up period. Tumor recurrence occurred primar ily in patients who had presented lymph node involvement (9/14, 64.3%). The 5-year survival rate was 66.1% for all patients. Important prognostic fact ors for overall survival were tumor stage (p < .004) and p53 accumulation ( p < .05) in univariate analysis, and tumor stage in multivariate analysis ( p < .001). Although p53 accumulation did not reach statistical significance in our small study group, it may be both important in the transformation o f low grade MALT lymphoma and an indicator for aggressive behavior in high grade tumors.