[BioC] GO summary of a list of genes?

[Ron]

Hello, after using statistical testing, we often obtain a list of genes. 
Could someone tell me what R/Bioconductor packages I can use to figure 
out what pathways/functions of these genes are in, e.g. a summary saying 
that 80% genes are related to breast cancer or 20% genes are related to 
glucose metabolism pathways? I guess these are GO-related packages.

Thanks. - Ron