A comparative analysis of two antigen retrieval techniques: Microwave oven and pressure cooker for immunoexpression of estrogen and progesterone receptors in breast cancer tissue

Antigen retrieval (AR) is an important step in Immunohistochemistry (IHC) which is used to unmask the antigenic sites and facilitate antigen-antibody binding. Adequate fixation of tissue is necessary to achieve consistent demonstration of tissue antigens that can be masked by the chemical process involved in formalin fixation and tissue processing. Out of the various methods of AR, heat-induced epitope retrieval (HIER) methods have greatly improved the quality and reproducibility of IHC. In this study, a comparison of the two most commonly used HIER methods-pressure cooker and microwave oven was done on thirty cases of breast carcinoma. Appropriate tumor sections were taken and subjected to manual IHC testing for estrogen receptor (ER) and progesterone receptor (PR) receptors in each case. The results were divided into technique and microscopy-based. The parameters assessed on microscopy were uniformity of nuclear staining, quality of nuclear staining, internal control staining, presence of background staining, and Allred score. The sensitivity and specificity and positive and negative predictive values for each method were calculated. The parameters assessed on microscopy were comparable for both methods. Using a microwave oven, the sensitivity and specificity for ER and PR were 94% and 100%, respectively. Using a pressure cooker, the sensitivity, and specificity for ER were 94% and 100%, respectively, and for PR were 88% and 100%, respectively. On technical aspects, the pressure cooker method offers the advantage of being more convenient due to the possibility of simultaneous handling of more slides and being more time efficient. Both the AR methods had comparable results on microscopy. However, the pressure cooker has the benefit of being both time and money efficient from a technical standpoint.