Carcinoma of the nasopharynx. Histopathological examination with supplementary immunohistochemistry.

One hundred and one nasopharyngeal malignancies, clinically accepted and treated as carcinomas, were histologically reviewed. Originally, all of them had been given the histopathological diagnosis of carcinoma or possible carcinoma. A wide variety of diagnostic formulations had been used, some of them inconclusive. The review was based on strict morphological WHO criteria, and a definite diagnosis was attained in most cases. Three of the neoplasms, however, did not fulfil the criteria of carcinoma, and were given the diagnosis of malignant tumour, probable lymphoma. Immunohistochemistry with routinely processed tissue was performed on 69 of the poorly differentiated non-keratinizing neoplasms, including the three possible non-Hodgkin's malignant lymphomas. The neoplasms were positive for cytokeratin PKK1 with four exceptions: the three possible lymphomas and a large cell tumour with epithelial growth and prominent nucleoli which was found to be positive only for neurone-specific enolase. Two of three possible lymphomas were verified as such by being positive for leucocyte common antigen. This study showed that the WHO classification is quite useful when strictly applied. The histopathological diagnosis of this category of neoplasms can easily be confirmed by immunohistochemistry on routinely processed material and this adjunct can usually resolve questionable cases.