Validation of tissue array technology in head and neck squamous cell carcinoma

BACKGROUND: The recent development of tissue array technology has potentiated large-scale retrospective cohort studies using archival formalin-fixed, paraffin-embedded tissues. This study evaluates the potential for using archival head and neck cancer tissue in such arrays. METHOD: Tissue array blocks were made from 184 head and neck cancer specimens. Three core tissue biopsies (0.6 mm x 3-4 mm) were taken from individual "donor" paraffin-embedded tumor blocks and arrayed into a new "recipient" paraffin block. Immunohistochemical (IHC) analyses were performed using antibodies recognizing cyclin-D1, Rb, and EGFR. IHC was scored on a 6-point scale for extent and a 3-point scale for intensity. We compared the staining of tissue array disks with staining of full tissue sections. RESULTS: Seventy-four percent (475 of 640) of samples placed into tissue arrays were confirmed to represent tumor tissue. The remaining samples were lost during processing or contained too few tumor cells. Only 6% of cases were completely lost, whereas 55%, 28%, and 11% of cases were judged on 3, 2, or 1 disk, respectively. Cohen's kappa coefficient was 0.66 for cyclin-D1, 0.40 for EGFR, and 0.41 for Rb. CONCLUSIONS: Tissue array technology is a rapid and efficient method for retrospective analysis of protein expression and is a promising tool for validation of prognostic markers in large series of head and neck squamous cell carcinomas. The agreement in scoring of the full section and the tissue arrays is reasonable. Discordance is probably due to intraobserver variation and lack of robustness of the scoring inherent of the proteins studied.