Histopathology

Low grade MALT lymphomas, recently reclassified as "extra-nodal marginal zone lymphomas of MALT-type," usually have a very favorable clinical course (Harris et al, 1999). Some MALT tumors may undergo high grade transformation. High grade diffuse large B-cell lymphomas may also arise de novo. Histologically, MALT lymphoma cells infiltrate reactive follicles in the region corresponding to the follicle's marginal zone, spreading diffusely into surrounding mucosa. The tumor cells may resemble germinal center centrocytes or small lymphocytes, or they may assume a monocyte-like appearance. An important feature of MALT lymphomas is the presence of lymphoepithelial lesions formed by invasion of individual glands by aggregates of lymphoma cells (Figures 33-1 and 33-2). The presence of scattered transformed blasts, plasma cell differentiation (which is maximal beneath the surface epithelium), and follicular colonization are characteristics of MALT lymphomas that indicate the cells of low grade gastric MALT lymphoma may be participating in an immune response. MALT lymphoma cells typically sur-

FIGURE 33-1. Active Helicobacter pylori gastritis complicated by a low grade extranodal marginal zone B-cell lymphoma (Mucosal-Associated Lymphoid Tissue [MALT] lymphoma). Note the neutrophils in the glands to the left and the atypical lymphocytes infiltrating and destroying the gland in the upper right hand corner (lymphoepithelial lesion). Figure donated by Professor Roger A. Warnke of the School of Medicine at Stanford University.

FIGURE 33-1. Active Helicobacter pylori gastritis complicated by a low grade extranodal marginal zone B-cell lymphoma (Mucosal-Associated Lymphoid Tissue [MALT] lymphoma). Note the neutrophils in the glands to the left and the atypical lymphocytes infiltrating and destroying the gland in the upper right hand corner (lymphoepithelial lesion). Figure donated by Professor Roger A. Warnke of the School of Medicine at Stanford University.

FIGURE 33-2. High magnification of a lymphoepithelial lesion. The gland in the center is being destroyed by the lymphoma cells. One of the epithelial cells is in mitosis. The surrounding lymphomatous infiltrate is composed of round and angulated lymphocytes together with occasional large lymphocytes, histiocytes, and plasma cells. Figure donated by Professor Roger A. Warnke of the School of Medicine at Stanford University.

FIGURE 33-2. High magnification of a lymphoepithelial lesion. The gland in the center is being destroyed by the lymphoma cells. One of the epithelial cells is in mitosis. The surrounding lymphomatous infiltrate is composed of round and angulated lymphocytes together with occasional large lymphocytes, histiocytes, and plasma cells. Figure donated by Professor Roger A. Warnke of the School of Medicine at Stanford University.

round reactive B-cell follicles in the distribution of the marginal zone and show a tendency to involve this zone when they disseminate to the lymph nodes and spleen. The B-cells of MALT lymphoma share the cytological features and immunophenotypes of marginal zone B-cells (CD20+, CD21+, CD35+, immunoglobulin [Ig]M+, and IgD-).

The primary lesion is submucosal and originates from the lymphoid tissue in the lamina propria. The invasion occurs outward though the serosa, invading the mucosa during the latter part of the disease process. The most commonly affected site is the antrum with the pylorus spared. The entire stomach or multifocal sites may be involved in 5 to 23% of cases. Grossly, the appearance of MALT lymphomas varies from small mucosal ulcerations to large fun-gating polypoidal masses. Lesions tend to be large with 30% of lymphoma lesions being > 10 cm. The tumor can occasionally take on the characteristics of a diffuse infil-trative process resembling linitis plastica.

Involvement of lymph nodes usually precedes distant metastases. The involvement of adjacent organ ranges from 7 to 29%, with the most common sites being the pancreas, omentum, and spleen. The colon can be occasionally involved with the development of a gastrocolic fistula as a secondary complication of PGL. It has been suggested that dissemination of MALT lymphoma is fostered by the mucosal homing receptor integrin, which is strongly expressed by secondary MALT lymphomas but not by the primary gastric lesion. High levels of integrin expression can also be induced in gastric lymphoma cells following activation by a Helicobacter pylori generated T-cell response. The ligand for integrin is the mucosal addressin cell adhesion molecule that is expressed both in the gastric mucosal and splenic marginal zones (Dogan et al, 1997).

Constipation Prescription

Constipation Prescription

Did you ever think feeling angry and irritable could be a symptom of constipation? A horrible fullness and pressing sharp pains against the bladders can’t help but affect your mood. Sometimes you just want everyone to leave you alone and sleep to escape the pain. It is virtually impossible to be constipated and keep a sunny disposition. Follow the steps in this guide to alleviate constipation and lead a happier healthy life.

Get My Free Ebook


Post a comment