Solitary epithelial cells in B cell gastric MALT lymphoma.

BACKGROUND Gastric mucosa associated lymphoid tissue (MALT) lymphoma is a low grade B cell lymphoma histologically characterised by neoplastic B cells surrounding follicles in a marginal zone pattern and selectively infiltrating epithelium to form characteristic lymphoepithelial lesions. AIMS To identify solitary epithelial cells in gastric MALT lymphoma and investigate their nature. METHODS Anonymised endoscopic biopsies from eight B cell gastric MALT lymphomas and 10 control biopsies from chronic atrophic gastritis were selected. The numbers of solitary cytokeratin positive epithelial cells were assessed both semiquantitatively and quantitatively in immunostained sections. Chromogranin A expression was studied in sections consecutive to those stained for cytokeratin. RESULTS Statistical analysis of the quantitative data confirmed that solitary epithelial cells were significantly more common in the lymphomas. The study of consecutive sections showed that the single cells express chromogranin A. CONCLUSIONS The presence of solitary, cytokeratin positive epithelial cells within the neoplastic infiltrate is a characteristic feature of gastric B cell lymphoma. These solitary epithelial cells are of neuroendocrine origin.