Christine Loo

Christine Loo

Prince of Wales Hospital

Title: Unusual findings in pap smears - possibilities and limitations of the PAP test


Christine Loo is an anatomical pathologist with a special interest in cytopathology and gynaecological pathology. In addition to being a fellow of the Royal College of Pathologists of Australasia, she is a member of the American Society of Cytopathology, member and previous NSW branch councillor of the Australian Society of Cytology and a Fellow of the International Academy of Cytology. Over 50,000 pap smears are reported each year in Southern IML Pathology and the laboratory is the major pathology provider in the region and processes over 30,000 surgical pathology specimens


The success of Pap smear screening programs in reducing the rate of cervical carcinoma in developed countries is well recognised. However, unusual findings are noted from morphological examination in a small number of Pap smears, some of which are unexpected findings that may significantly influence clinical management of the patient. More common examples include abnormal endometrial cells, organisms and foreign materials. Rarely, unusual types of cervical and uterine carcinomas, primary and metastatic, are identified in the Pap smears. Here cases with unusual Pap smear findings, some which were not clinically suspected before the Pap tests including examples of unusual malignancies are presented. These cases illustrate the usefulness but also the limitations of the Pap test. There are also common factors that can influence the diagnostic yield. In these examples, available clinical information, sampling methods and availability of material for ancillary tests were the major factors that helped to reach the diagnosis. Difficulties arose from problems due to poor tissue preservation, cellular distortion and lack of material for ancillary tests. The cytological assessment was based mainly on morphology of routine smears and a wide range of differential diagnoses were considered. Both conventional and liquid based Pap tests can offer additional information beyond the diagnosis of cervical dysplasia. Appropriate sampling and communication between referring doctors and the laboratory is necessary.