Genetic alterations and growth pattern in biliary duct carcinomas: loss ofheterozygosity at chromosome 5q bears a close relation with polypoid growth

Biliary duct carcinomas (BDCs) are relatively rare and the carcinogenic mec hanisms underlying their induction are poorly understood. There are two gro wth patterns, polypoid and non-polypoid infiltrative type, but little infor mation is available concerning the relation between growth pattern and gene tic alterations. ih comparative study was therefore conducted to clarify if differences in genetic changes, including loss of heterozygosity (LOH) at 5q, 9p, 17p, and 18q, and K-ras mutations exist between polypoid and non-po lypoid infiltrative type BDCs. LOH analysis was performed using microsatell ite markers and K-ras point mutations were analysed by dot blot hybridisati on. The incidences of changes for polypoid and non-polypoid infiltrative ty pes were 73% and 26% on 5q, 63% and 59% on 9p, 55% and 50% on 17p, and 20% and 18% on 18q, and 25% and 27% for K-ras mutations. Most importantly, we f ound the frequency of 5qLOH to be significantly higher with polypoid growth than in the non-polypoid infiltrative type (p<0.05), especially in extrahe patic duct carcinomas (p<0.05). The incidences of other genetic alterations (LOH at 9p, 17p, and 18q, and K-ras mutations) showed similar rates with b oth tumour types. The present data suggest that 5qLOH may have a close rela tion with polypoid growth in BDCs.