Role of immunostaining in cytopathology

The majority of malignant tumours are diagnosed cytologically with a high accuracy rate. However, expectations have now risen to a much higher level. The cytopathologist is expected to subtype the malignancy, define the possible site of primary when unknown clinically or when two primary tumours are in question, and also provide information that is helpful in selecting therapy and predicting prognosis. All these expectations pose new challenges to cytopathologists who often deal with limited cytologic material. In facing these new demands, immunocytochemistry has emerged as a useful adjunct to cytomorphology. Immunocytochemistry has become a suitable tool for the new tasks. Some of the advances in the application of immunostaining in cytopathology are summarized in this review.