Fluorescent in situ hybridization evaluation of p53 gene deletions at a tumor interface of lingual carcinoma

Objective/Hypothesis: To evaluate the ability of fluorescent in situ hybrid ization (FISH) to detect malignant cells missed by standard histological as sessment at an interface between malignant and normal tissue in lingual squ amous cell carcinoma (SCC) and to correlate findings of FISH assessment wit h patients' clinical stages. Study Design: Retrospective assessment of arch ival tissue from 31 patients with lingual SCC treated at University of Wisc onsin Hospital and Clinics in Madison. Methods: An assay combining standard histological and FISH techniques was used to assess a tumor interface tiss ue section and allow identification of each tumor's ploidy characteristics and p53 gene deletions and the presence or absence of malignant cells withi n tissue viewed as "normal" on histological review. Results: Forty-five per cent of tumors (14 of 31) demonstrated ploidy changes and 84% (26 of 31) sh owed p53 deletions. Of these 26 tumors with p53 deletions, 14 were found to have "microfoci" with p53 deletions within tissue that appeared normal on histological examination. These microfoci were found in 75% of late-stage t umors and in only 35% of early-stage tumors. Conclusions: FISH allowed iden tification of malignant cells in tissue viewed as normal on standard histol ogical assessment, and this finding occurred more frequently in late-stage tumors.