Short-term cultures of a collagenase disaggregated ameloblastoma previously diagnosed as an adenoid cystic carcinoma of the salivary gland were shown by cytogenetic analysis to have the clonal karyotype 45,XY,del(10)(p12),-22. The data may indicate that the loss of genes of chromosome 22, as well as of 10p, could be a critical event in the evolutionary pattern of odontogenic neoplasias.