Diagnostic utility of cell block technique as an adjunct to cytological smears in evaluation of thyroid aspirates on fine needle aspiration cytology

Background: Direct smears and cell blocks prepared from residual tissue fluids complement each other for establishing a conclusive cytopathologic diagnosis in thyroid lesions. Aim of the Study: Evaluation of the diagnostic utility of fine-needle aspiration cytology (FNAC) alone and in combination with cell blocks in the diagnosis of thyroid lesions. Materials and Methods: A hospital-based prospective longitudinal study was conducted in which 100 thyroid smears were categorized as neoplastic, nonneoplastic and inadequate using FNAC and cell block technique. All specimens were classified using point scoring system modified by Mair et al. Direct smears were compared with cell-block specimens on variables of cellularity, background blood and clot, cellular degeneration and retention of appropriate architecture using Fisher's exact and unpaired t-test. Results: Sixty-two percent of cell block specimens showed a moderate amount of background material (P = 0.01), display of excellent architecture was also significantly more in cell block (20%) technique than direct smears (9%), and degree of cellular degeneration was minimal in significantly more cell blocks (26%) than direct smears (12%), thereby making diagnosis easy as opposed to FNAC which yielded more cellular material than cell blocks (P = 0.02). Four cases showing hemorrhagic material on direct smears were diagnosed on cell block as one case each of colloid goiter and chronic lymphocytic thyroiditis and two cases of adenomatous goiter and two cases showing hemorrhagic material on cell block were diagnosed with chronic lymphocytic thyroiditis on direct smears. Conclusion: FNAC and cell block complement each other and combining both techniques improves the diagnostic yield and facilitates accurate diagnosis. It is advisable to perform cell-block for each case of FNAC of thyroid lesions.