Is it time for a unified two‐tier reporting system for cervical cytology and histology in the cervical screening programmes?

In this edition of Cytopathology, invited reviews and a Clinical Perspective from recognised experts address the often debated issue of terminology and classification of cervical cytology and histology specimens and in particular whether going forward a two-tier rather than a three-tier system should be adopted. Professor Herrington makes a convincing argument for the adoption of a two-tier system for reporting pre-invasive cervical squamous neoplastic lesions based on our knowledge of the biology of human papillomavirus infection of the cervix, and this reflects the recommendations of the Lower Anogenital Squamous Terminology (LAST) project described by Dr Darragh. Historically, a three-tier system for reporting cervical cytology was adopted in the second half of the 20th century by translation from grading systems used for histology reporting at other epithelial sites such as the respiratory and gastrointestinal tract. More recently, two-tier systems of low-grade and high-grade dysplasia have been adopted to address issues of interand intra-observer reproducibility. The three-tiered British Society for Clinical Cytology (BSCC) system for grading dyskaryosis, proposed in 1986 and subsequently adopted by the NHS Cervical Screening Programme, was dependent on the assessment of the nuclear–cytoplasmic area ratio of cells with nuclear morphological features of neoplasia. This is in contrast to the Bethesda system introduced slightly later in which grading of abnormality was principally dependent on comparison of the size of neoplastic nuclei with a fixed internal comparator, intermediate cell nuclei, as described by Drs Nayar and Wilbur. Subsequently, it was shown that in both the BSCC and Bethesda systems a binary system of distinguishing highfrom lowgrade cytological abnormality based on the assessment of the nuclear–cytoplasmic diameter rather than area or relative nuclear size, respectively, resulted in a more scientifically robust distinction. This observation, coupled with a desire to bring BSCC terminology in line with the Bethesda system, which had been adopted widely internationally, resulted in the development and introduction of the revised binary BSCC terminology of low-grade and high-grade squamous dyskaryosis in the UK cervical screening programmes. Whatever terminology is used for cervical cytology and histology it must be clinically relevant and clearly understood by clinicians. Prendiville is clear in his view that global adoption of a two-grade system, supported by rigorous quality assurance, would be welcomed by the colposcopy community. In conclusion, all four articles support the adoption of a two-tiered system for reporting cervical cytology and histology soundly based on our knowledge of the natural history of HPV infection of the cervix. The UK cervical screening programmes have adopted a two-tier system albeit using different terminology from Bethesda and the LAST project. It only remains now to make the final step to adoption of lowand high-grade squamous intraepithelial lesion and truly bring British terminology in alignment with that widely used internationally, and recently supported by the World Health Organisation.