IMMUNOCYTOCHEMISTRY IN DIAGNOSTIC CYTOLOGY: CONTEMPORARY APPLICATIONS AND CHALLENGES

Abstract

Immunocytochemistry (ICC) has emerged as a vital ancillary technique in diagnostic cytology that enhances the precise identification and categorization of diseases, particularly malignancies. Utilizing antigen–antibody reactions, ICC enables the detection of specific cellular proteins and biomarkers across various cytological specimens, including fine-needle aspiration cytology (FNAC), body fluids, Pap smears, and brush cytology samples. In contemporary laboratory medicine, ICC is widely used to differentiate benign from malignant lesions, determine the origin of metastatic tumors, and guide targeted therapy decisions. Progressive incorporation of cell block preparation, automated staining, digital pathology, and molecular techniques has further expanded its diagnostic utility. Notwithstanding these advancements, significant challenges remain, including technical limitations, inadequate specimen preservation, elevated costs, absence of standardization, and interpretive variability. This chapter examines the principles, methodology, applications, recent advancements, and limitations of ICC in diagnostic cytology, and highlights future directions such as artificial intelligence integration, multiplex ICC, and precision biomarker diagnostics. Overall, ICC continues to strengthen the role of cytology in modern patient care by improving diagnostic accuracy and supporting evidence-based clinical decisions.