Validation of tissue microarray technology in vulvar cancer

The aim of the study was to validate tissue microarray (TMA) for vulvar cancer by comparing immunohistochemical staining results of triplicate core biopsies on TMA with the results of full section analysis. The study material consisted of slides and selected tissue blocks from 40 patients with vulvar cancer. A TMA was constructed with 3 cores/case. Both the TMA and the slides were stained with the same antibodies against COX-2, Caspase-3, epidermal growth factor receptor, p16INK4, Cyclin D1, and Ki67. For COX-2, 2 different scoring systems were applied. Agreement in the readings between TMA and slides was expressed in total agreement and kappa. Expression patterns of antibodies can be reproduced on TMA with good reliability (kappa 0.68 to 0.75) for Ki-67, p16INK4, COX-2, Cyclin D1, and epidermal growth factor receptor in comparison with whole slides. For Caspase-3 agreement is only slight with a kappa of 0.40. The majority of discordant cases for COX-2 and Ki67 were negative on slide and positive on TMA. For epidermal growth factor receptor and Caspase-3 an opposite pattern was found. For COX-2, the use of an alternative scoring system resulted in a decrease of kappa from 0.68 to 0.21. Agreement between results on TMA and slides depends on the distribution of the protein in the cancer tissue and on the scoring system used.