Validation of on‐slide immunocytochemistry controls prepared from long‐term preserved prefixed cell suspensions

The described method offers a robust, practical, and adaptable solution for preparing on-slide controls applicable to all cytology preparations, including previously stained and mounted slides. Implementing this approach strengthens quality control for non-cell block cytology slides, enhances diagnostic reliability, and brings cytology practice closer to the quality standards established in immunohistochemistry.