Mitochondrial DNA (mtDNA) has been proposed to be involved in carcinogenesis and ageing. The mtDNA 4977 bp deletion is one of the most frequently observed mtDNA mutations in human tissues and may play a role in breast cancer (BC). The aim of this study was to investigate the frequency of mtDNA 4977 bp deletion in BC tissue and its association with clinical factors.

We determined the presence of the 4977 bp common deletion in cancer and normal paired tissue samples from 106 Vietnamese patients with BC by sequencing PCR products.

The mtDNA 4977 bp deletion was significantly more frequent in normal tissue in comparison with paired cancer tissue. Moreover, the incidence of the 4977 bp deletion in BC tissue was significantly higher in patients with estrogen receptor (ER) positive as compared with ER negative BC tissue. Preliminary results showed, in cancerous tissue, a significantly higher incidence of novel deletions in the group of patients with lymph node metastasis in comparison with the patients with no lymph node metastasis.

We have found 4977 bp deletion in mtDNA to be a common event in BC and with special reference to ER positive BC. In addition, the novel deletions were shown to be related to lymph node metastasis. Our finding may provide complementary information in prediction of clinical outcome including metastasis, recurrence and survival of patients with BC.