Nasopharyngeal carcinoma: The role of immunohistochemistry and electron microscopy in differentiation between undifferentiated carcinoma and malignant lymphoma: Report of 10 cases and review of literature

Undifferentiated nasopharyngeal corcinoma is frequently misdiagnosed as large cell malignant lymphoma. The aim of this study is to evaluate the diagnostic role of immunohistochemistry and electron microscopy in this tumor. 81 cases of nasopharyngeal carcinoma were studied. Patients ranged from 9-90 years in age (mean: 48.5 years). The age incidence curve was bimodal with two peaks in 2-3 and 5-6 upper cervical mass was the first manifestation of the tumor in the majority (87.6%) of cases. Microscopically most o tumors were undifferentiated nasopharyngeal carcinoma, Who type III. Differentiation between undifferentiated nasopharygeal carcinoma and malignant lymphoma, large cases cell type was not possible in 12. Ten of these cases were chosen for immunohistochemical and electron microscopy studies.In our cases cytoplasmic reactivity for cytokeratin and/or epithelial membrane antigen was persent. These tumors possessed desmosomes and tonofilaments in eletron microscopy.While in malignant lymphoma (three cases) tumor cells had leukocytic common antigen remaining. They were discohesive and had irregular nuclei. In the cases, the studies were inconclusive