PMC3234051_01
At diagnosis the gastric biopsy is heavily infiltrated by a dense population of small and medium-sized lymphocytes, which form lympho-epithelial lesions with the gastric glands and are immunoreactive for CD20 (A). Interphase FISH, using the LSI MALT1 Dual Color, Break Apart DNA Probe, showed split signals in most of the nuclei analysed; a pattern consistent with the occurrence of an 18q21 locus translocation involving the MALT1 gene (B). After therapy, the gastric biopsies showed a few, small, well-demarcated lymphoid nodules (C), containing rare lymphocytes with membranous immunofluorescence for CD20; two discrete API2 (green fluorescence) and MALT1 (red fluorescence) signals can be observed suggesting the absence of the t(1118)(q21q21) translocation and therefore of minimal neoplastic involvement (D).
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Pathological evaluation showed gastric mucosa heavily infiltrated by a dense population of small and medium-sized lymphocytes immunoreactive for CD20, which formed lympho-epithelial lesions within the gastric glands (Figure 1A). This pattern was consistent with the occurrence of an 18q21 locus translocation, involving the MALT1 gene (Figure 1B), that was further characterized as at (1118)(q21q21) by using the LSI  API2/MALT1 Dual Fusion Translocation probe (Vysis, Inc., Downers Grove, IL, USA). In particular, gastric biopsies were characterized by small lymphocytes and plasma cells isolated in the lamina propria or forming small well-demarcated nodules (Figure 1C), with a normal pattern of the MALT1 and API-2 genes by interphase dual colour FISH (Figure 1D).
Upper Gastrointestinal Endoscopy. During endoscopic follow-up, a macroscopic recurrence of the lesions of the gastric greater curvature was observed, showing cobblestone appearance and a small 5 mm ulceration of the mucosa. Biopsies were positive for disease (A and B). Six months after radioimmunotherapy an upper gastrointestinal endoscopy showed chronic atrophic gastritis. Biopsies were negative for disease (C and D).
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Four different endoscopic evaluations (UGE with multiple gastric biopsies and EUS) and total body CT scans were performed at two, four, six and 12 months from Zevalin administration, showing a clinical and pathological complete response (Figures 2C-D).