Validation of tissue microarrays using p53 immunohistochemical studies of squamous cell carcinoma of the larynx

Tissue microarrays are a powerful new tissue-conserving technology in the study of cancer, allowing simultaneous study of a large number of tumor specimens. We sought to ascertain the utility of tissue microarrays in head and neck cancer pathology using squamous cell carcinoma of the larynx as a model system. Whole-specimen slides from 44 different laryngeal squamous cell carcinomas were stained for p53 expression. Microarrays were then generated by taking six 0.6-mm core biopsies from each of the 44 specimens. The whole sections and the microarrays were independently scored for p53 expression. Twenty-three (53%) of the 44 tumor specimens were positive for p53. Forty-four of the 264 core biopsies (17%) were not given a score because of the lack of tumor cells. Seventy-eight percent of the individual discs on the microarray had scores in agreement with those of the whole-section slides. Among biopsy discs with tumor cells present, 94.5% were in agreement with the whole-section slide. The average probability that four randomly chosen biopsy discs, considered together, would accurately identify the presence of p53 staining in a whole section was 0.97 (95% CI.93-1.0). We conclude that tissue microarrays for squamous cell carcinomas can accurately represent immunohistochemical results of whole-slide specimens when four or more samples are used. Tissue microarrays are an important technique that may be applied to immunohistochemical studies of head and neck cancer.