Fig. 3

 A and B Light examination of tumour, low magnification (haematoxylin and eosin stain, original magnification × 20), A Pseudo-nodular architecture of the excised lesion with some colonised lymphoid follicles with widened mantle zone in the MALT lymphoma, B Massive colonisation of the neoplastic follicles; tumour cells are scattered and infiltrate adjacent cellulo-adipose tissue with insheathing of the small nervous fillets (yellow arrow), but do not invade the healthy lobule of salivary gland (black arrow). No epithelial or salivary structure is observed in the tumour infiltrate, C Tumour cells of small size with an abundant and pale cytoplasm and irregular nuclei; these cells have rather dense chromatin nuclei with a cytoplasm sometimes off-centred and a plasma-cell differentiation (original magnification × 40). D, E Immunohistochemical staining (original magnification × 40), D Strong positive for CD20, E Strong positive for CD79a. F Uniform strong staining of membrane cells for IgM (original magnification × 20). G, H In situ hybridisation for light chain of immunoglobulin (original magnification × 40) G High expression of kappa light chain H Absence of the expression of lambda light chain