Influence of temperature on long-term keratin immunoreactivity for oral exfoliative cytology

We previously showed that keratin profiles can be of value in the diagnosis of oral cancer when using exfoliative cytology. In the future, they may form part of a screening program for oral cancer. This study evaluated the influence of long-term storage on keratin expression. Smears were collected from the clinically normal buccal mucosa and dorsal tongue of 22 patients. Half were stored in a refrigerator (5 degrees C) and half in a freezer (-70 degrees C). A total of 528 smears were collected. A panel of three antikeratin antibodies (LP34, AE8 and 1C7) was used to identify the preservation of keratin expression (graded as absent, few cells positive or many cells positive). The results for smears from dorsal tongue indicated that many cells were impermeable by the antikeratin antibodies. However, a satisfactory level of keratin immunoreactivity was observed in smears from buccal mucosa stored at -70 degrees C for over one year. Results for storage at 5 degrees C for both sites were inadequate after one month. Thus, smears from nonkeratinized oral sites may be stored at -70 degrees C for at least one year without a profound loss of keratin immunoreactivity, thus allowing examination of archival material.