Confocal Laser Endomicroscopy as Diagnostic Tool for Gastrointestinal MALT-lymphoma

Introduction

Extranodal marginal zone B-cell lymphoma (MZBL) of the mucosa associated lymphoid tissue (MALT-lymphoma) is the most common form of extranodal lymphoma [1, 2]. Although MALT-lymphoma may involve different organs, the stomach represents the site of predilection of this malignant disease. About 90% of gastric MALT-lymphomas are associated with infection with Helicobacter pylori (HP) [3] and eradication of the pathogen leads to tumor regression in a high percentage of patients at early tumor stages [4, 5]. Relapses after HP-eradication and primary advanced tumor stages require chemotherapeutic treatment, radiation therapy and, in some cases, surgery [6]. Following complete remission lifelong follow-up examinations should be performed in order to detect relapses [7].

Histologically, MALT-lymphoma is characterized by an infiltration of the lamina propria by lymphomatous centrocyte-like cells that spread into the surrounding mucosal layers [8]. In immunohistochemistry they show CD 20 positive staining properties. When they spread to lymph nodes or spleen they accumulate typically within the marginal zone (for this reason they are classified as "marginal zone lymphoma") [2]. Dissemination to other organs, especially to other mucosal sites may occur frequently wherefore detailed diagnostics are required during MALT-lymphoma staging and follow-up. Spreading within the gastrointestinal tract (GI-tract), to the small bowel, for example, is rare, but can be assessed very easily with standard endoscopic procedures as recently reported at our department [9].

For gastric MALT-lymphoma gastroscopy with biopsy assessment is the current follow-up examination of choice. Multiple biopsies should be taken randomly from all gastric sites and specifically from all suspicious lesions. Recent developments for the enhancement of the tissue contrast during the endoscopic examinations (chromoendoscopy or Narrow Band Imaging, for example) helped to detect MALT-lymphoma lesions. Nevertheless, detection rates hardly changed, since all these techniques rely on the presence of superficial features[10].

An endoscopic technique that allows an evaluation of deeper wall layers is endoscopic ultrasonography. During the last years it has become an important amending tool in the diagnostic management of gastric MALT-lymphoma. Although it provides essential information about tumor infiltration depth and lymph node involvement in the context of staging procedures, it cannot replace histological assessment during follow-up, since endosonographic findings do not show a good correlation to histological results over time [11, 12].