Oral leukoplakia transplanted to nude mice.

Thirty-eight biopsies of homogeneous oral leukoplakias were transplanted to subcutaneous sites of nude mice and protected from overlying cutaneous tissue by Millipore filters. The transplants were recovered after 21 d with a rate of successful recovery of 66%. The histologic epithelial features of the transplants were compared with those of the original leukoplakias. None of the leukoplakias from patients without tobacco habits lost the preexisting keratinization, whereas all 10 transplants demonstrating loss of keratinization belonged to patients with tobacco habits. This difference in behavior of transplanted leukoplakias from patients with and from patients without tobacco habits was statistically significant (P = 0.028). The results of the experimental study support the concept of two different types of leukoplakia, one possessing irreversible changes in epithelial keratinization, the other showing reversibility.