Quality control of immunohistochemical studies in Russia in 2025: achievement and prospects

Immunohistochemistry is one of the key methods of modern morphological diagnostics, providing both differential diagnosis of neoplastic and non-neoplastic processes and the assessment of prognostic and predictive biomarkers relevant for the selection of drug therapy. The multistep nature of immunohistochemical studies is associated with a high risk of methodological errors at the preanalytical, analytical, and postanalytical stages, which may lead to reduced reproducibility of results and the development of clinically significant diagnostic inaccuracies. OBJECTIVE: To assess the quality of immunohistochemical studies at all stages of the laboratory workflow in medical institutions participating in the external quality assessment program of the Immunohistochemistry Quality Control Center of the Russian Medical Academy of Continuous Professional Education in 2025. MATERIAL AND METHODS: The results of 18 external quality assessment rounds covering the preanalytical, analytical, and postanalytical stages of immunohistochemical studies were analyzed. Expert evaluation was performed by the Expert Council of the Immunohistochemistry Quality Control Center in accordance with approved assessment criteria and current clinical guidelines. RESULTS: At the preanalytical stage, typical violations related to fixation and histological processing of biological material were identified, significantly affecting the quality of immunohistochemical and molecular genetic studies. At the analytical stage, the main causes of unsatisfactory results were insufficient intralaboratory validation of protocols, the use of non-recommended antibody clones, and the absence of adequate control samples. At the postanalytical stage, errors in result interpretation not compliant with current clinical guideline requirements were detected. Laboratories that repeatedly participated in external quality assessment rounds demonstrated a statistically significant improvement in results following the implementation of individualized expert recommendations. CONCLUSION: External quality assessment of immunohistochemical studies is an effective tool for improving the reproducibility and clinical relevance of morphological research results. Regular participation of laboratories in quality control programs, standardization of methodological approaches, and systematic professional training of specialists contribute to a reduction in diagnostic errors and to improving the quality of morphological diagnostics and personalized patient management.