Comparison of Fixation Methods for Preservation Cytology Specimens of Cell Block Preparation Using 10% Neutral Buffer Formalin and 96% Alcohol Fixation in E-cadherin and Ki-67 Immunohistochemical Examination.

Background: Cytological and molecular examinations are among the most important examinations in cancer diagnosis. 96% alcohol is a fixative solution commonly used by clinicians for cytological samples because of its accessibility and affordability. Cellblock preparation from cytology specimen may increase morphology detail and may be used for further biomarker analysis. E-cadherin is an adhesion protein expressed in the cell membrane of most carcinoma. Ki67 is a protein expressed in nuclei of malignant cells that used as a proliferation marker.

Aim: This study was designed to investigate the effect of fixation duration in 96% alcohol on protein preservation for immunohistochemistry (IHC) evaluation compared to 10% neutral buffered formalin (NBF) as the gold standard.

Methods: Twenty-five fine-needle aspiration biopsy (FNAB) specimen diagnosed as carcinoma were fixed in 10% NBF and 96% alcohol for 1 hour, 6 hours, 24 hours, 48 hours and 72 hours. Cell blocks preparation were made from those 6 groups of specimens. E-cadherin and Ki67 IHC were done to cell blocks section and evaluated. The data were statistically analysed using the Friedman test with p-value < 0.05 of a significant level.

Results: There were significant differences between E-cadherin and Ki67 expression in cell block preparation from 96% alcohol-fixed cytology specimen for 1 hour, 6 hours, 24 hours, 48 hours and 72 hours to 10% NBF (p = 0.0001).

Conclusion: The result indicated that 96% alcohol is not suitable as a fixative solution for cell block preparation in E-cadherin and Ki-67 IHC examination.