LOW-FREQUENCY OF LOSS OF HETEROZYGOSITY AT THE NEVOID BASAL-CELL CARCINOMA LOCUS AND OTHER SELECTED LOCI IN APPENDAGEAL TUMORS

Previous studies of loss of heterozygosity (LOH) have revealed distinc t patterns of allelic loss in some skin tumors. In basal cell carcinom as (BCCs) loss of heterozygosity is virtually restricted to chromosome 9, whereas in squamous cell carcinomas (SCCs) and actinic keratoses l oss is more widespread involving chromosomes 3, 9, 13, and 17. Because there are histological similarities between BCCs and some appendageal tumors, and because some lines of evidence suggest that BCCs are appe ndageal in origin, we carried out a limited allelotype in 41 appendage al tumors. The overall frequency of allelic loss was low (4 out of 247 informative loci; 1.6%). LOH was seen in a proliferating trichilemmal cyst (17p), a sebaceous epithelioma (17q), an eccrine porocarcinoma ( 17q), a trichoepithelioma (9q), and in two basal cell carcinomas showi ng eccrine or granular cell differentiation that were originally misdi agnosed (9q)/. The pattern of loss in this mixed group of appendageal tumors shows differences from both BCCs and SCCs, and further emphasiz es the unique genetic profile and behavior of BCCs. The finding of 9q loss in BCCs with eccrine or granular cell differentiation shows that 9q loss occurs in different histological subtypes of BCCs.