Comparison of heat induced antigen retrieval techniques for immune-histochemical estrogen receptor expression in ductal carcinoma of breast in females.

OBJECTIVE To compare immunohistochemical estrogen receptor expression on formalin-fixed, paraffin-embedded breast carcinoma tissue sections by using regular, extended microwave heating and pressure cooker technique for heat induced antigen retrieval. STUDY DESIGN Quasi experimental study. PLACE AND DURATION OF STUDY Department of Histopathology, Armed Forces Institute of Pathology, Rawalpindi, from August 2006 to July 2007. METHODOLOGY The study was conducted on 40 cases of breast carcinoma diagnosed on histopathology and selected by convenience sampling. One section each of the tumour was separately subjected to regular microwave heating (10 minutes), extended microwave heating (20 minutes) and pressure cooker (heating for 2 minutes after reaching full pressure). A nuclear staining of >10% cells with moderate intensity was considered positive and frequency of ER expression by each technique was compared statistically. Sensitivity and specificity of the techniques was determined using pressure cooker technique as the gold standard for this study. RESULTS Out of 40 cases, ER expression in 24 (60%) cases was seen by microwave regular heating (MRH) and in 30 (75%) cases by microwave extending heating (MEH) technique. Pressure cooker (PC) technique for antigen retrieval demonstrated 34 (85%) cases with ER expression. Out of 16 which were negative by MRH technique, 6 became positive by MEH while 10 became positive by PC. Statistically significant difference in ER expression by PC and MEH technique was seen in comparison to MRH with a p-value of <0.05. Moreover, 4 cases which were negative by MEH technique turned positive for ER expression by PC. MRH and MEH had 100% specificity but sensitivity was 70.6% and 88.2% respectively taking PC technique as gold standard with diagnostic accuracy of MEH as 90% and MRH as 75%. CONCLUSION Pressure cooker antigen retrieval technique is a better method than microwave heating. The increase in duration of heating improves the percentage of positive cells as well as intensity of ER immuno-staining which entitles breast cancer patient to benefit from ER positive treatment protocols which have better prognosis.