We explored the feasibility of studying loss of heterozygosity (LOH) by using exome sequencing and compared the differences in genetic LOH between primary breast tumors and metastatic lesions. Exome sequencing was conducted to investigate the genetic LOH in the peripheral blood, a primary tumor, and a metastatic lesion from the same patient. LOH was observed in 30 and 48 chromosomal loci of the primary tumor and metastatic lesion, respectively. The incidence of LOH was the highest on chromosome 19, followed by chromosomes 14, 3, and 11 in the metastatic lesion. Among these 'hot' regions, LOH was observed for multiple genes of the CECAM, MMP and ZNF families. Therefore, the use of exome sequencing for studying LOH is feasible. More members of gene families appeared with LOH in 'hot' regions, suggesting that these gene families had synergistic effects in tumorigenesis.