General principles of cytological interpretation

THE aim of cytological evaluation is to establish an aetiological and/or morphological diagnosis for a lesion and thereby obtain a more accurate prognosis. The technique offers many advantages over surgical biopsy and histopathology. As described in the last issue (pages 370-377), samples can be collected quickly, easily and inexpensively; also, being less invasive than surgical biopsy, cytology gives rise to fewer complications. On the basis of cytology, lesions can be categorised as inflammatory (septic or non-septic) or non-inflammatory (hyperplastic, dysplastic or neoplastic). If neoplastic, an attempt can be made to ascertain the origin of the cells present and to assess the degree of malignancy. In this article the principal cytological features of inflammatory disease and neoplasia are described. An article in the next issue will focus on the collection and handling of pleural and peritoneal effusions.