Antigen retrieval: p53 staining in benign, pre-malignant and malignant tissues of the larynx

Antigen retrieval techniques have been reported to increase p53 detection. Using an antigen retrieval technique applied to immunohistochemistry, a study was performed on 67 laryngeal lesions (21 benign, 16 carcinoma in situ, 30 squamous cell carcinoma). p53 staining was observed in 30% of carcinoma in situ specimens and 53% of squamous cell carcinomas but was not detected prior to antigen retrieval in any benign lesion. However, over-expression of p53 was identified in 92.5% of benign lesions after antigen retrieval using the microwave oven heating. There was also increased p53 staining in both the carcinoma in situ (43.7%) and squamous cell carcinomas (30.0%) after antigen retrieval. We conclude that antigen retrieval using microwave oven heating increases immunohistochemical detection of p53 such that positive staining is observed in benign conditions. We postulate that this apparent over-expression is a manifestation of the wild-type protein, which may be found in more evidence in basal cells than suprabasal cells. Our results thus offer a cautionary note to such studies involving squamous cell cancers that attempt to correlate p53 over-expression with clinical parameters.