CLASSIFICATION OF PRIMARY GASTRIC LYMPHOMAS ACCORDING TO HISTOLOGIC FEATURES

Histologic features of low-grade gastric lymphomas of mucosa-associate d lymphoid tissue (MALT) have been extensively described, and transfor mation to a large cell (high-grade) lymphoma can occur. We characteriz e high-grade gastric lymphoma histologically in an attempt to distingu ish between MALT-type and non-MALT-type lesions. We studied a series o f 60 gastric lymphomas and characterized them clinically, histopatholo gically, and immunophenotypically. Low-grade gastric lymphomas were cl assified according to established criteria. High-grade lymphomas were classified in three groups based on the presence or absence of a low-g rade component and lymphoepithelial lesions (LELs): 1) high-grade MALT lymphomas appearing in low-grade MALT lymphomas (LG/HG MALT lymphoma) ; 2) large cell lymphoma with LELs composed of large cells (high-grade LELs) but without a low-grade component (HG MALT lymphoma); and 3) di ffuse large cell lymphoma without a low-grade MALT lymphoma component or LELs (DLCL). Twenty-two lymphomas were classified as low-grade MALT lymphomas, 16 as LG/HG MALT lymphomas, 10 as HG MALT lymphomas, and 1 2 as DLCL. B-cell immunophenotype was confirmed in all 55 cases in whi ch immunophenotyping was performed. Low-grade LELs were seen in all lo w-grade MALT lymphomas, and CD20(L26) expression confirmed B-cell phen otype in the LELs in 20 of 20 cases. Clinical follow-up was available for 56 patients (range, 1-264 months; mean, 57 months). Actuarial anal ysis of disease-specific survival and relapse-free survival showed tha t clinical stage was highly statistically significant (P < 0.0001), wh ereas histologic type and grade approached statistical significance. M ultivariate analysis showed that clinical stage was the only significa nt factor in relapse-free and disease-specific survival.