Infiltrating lymphocytes in undifferentiated nasopharyngeal cancer lack metallothionein expression

Metallothionein (MT) is a metal-binding protein with functional roles in ce ll growth, repair and differentiation. MT is reported to be differentially expressed in lymphocytes of malignant gastrointestinal lesions. The level o f MT protein was examined by immunohistochemical analysis at light microsco pic and ultrastructural level in infiltrating lymphocytes from 20 cases of undifferentiated nasopharyngeal carcinoma (NPC). MT expression was found to be absent in the infiltrating lymphocytes of NPC and in reactive lymphocyt es of lymphoid hyperplasia in nasopharyngeal tissues. Ultrastructural exami nation confirmed the absence of MT immunoreactivity in the lymphoid infiltr ate of NPC. On the other hand, malignant lymphoblasts of diffuse large cell lymphoma, showed MT-immunopositivity by immunoelectron microscopy. This st udy demonstrates a lack of MT expression in the lymphoid stroma of undiffer entiated NPC, a further characteristic of its non-neoplastic nature. (C) 20 00 Elsevier Science Ireland Ltd. All rights reserved.