e12582 Background: It has been demonstrated an increased risk of breast cancer (BC) incidence in patients with previous cervical dysplasia, suggesting a role of human papillomavirus (HPV) of cervical lesions in the development of BC. Although, the origin of HPV spreading to the mammary gland and its mechanism of dissemination is not clear. Methods: Seven serum samples from healthy donors and 58 from early BC patients collected pre-surgery were analyzed for the presence of HPV DNA. For 49/58 patients HPV DNA was analyzed also on the primary tumor tissue. 17 patients had luminal A BC (4 relapsed, 13 non relapsed), 16 had luminal B BC (5 relapsed, 11 non relapsed), 13 had triple-negative BC (6 relapsed, 7 non relapsed), 12 had HER2-positive BC (4 relapsed, 8 non relapsed). Circulating DNA was extracted from 500 μl of serum by Qiamp DNA Mini kit (Qiagen, Milan, Italy) and tumor DNA was extracted from at least four 10-micron sections by QIAamp DNA FFPE Tissue Kit (Qiagen, Milan, Italy). Circulating HPV DNA was amplified by a multiplex PCR with HPV E6 or E7 gene-specific primers and the sequence was assessed by a high-throughput MALDI-TOF mass spectrometry-based method. Results: HPV DNA was detected in only 5 serum of BC patients and in none of the healthy controls. 4/5 BC cases had high-risk HPV DNA (type 39,45,52,59) and 1 had type 73 low-risk HPV DNA. 4/5 HPV DNA-positive patients had previously low-grade cervical intraepithelial neoplasia (CIN I) detected by Pap smear. These 5 patients with circulating HPV DNA did not show HPV positivity in the BC tissue. 2 out of 49 cases were positive for universal HPV DNA sequence in tissue and only 1 case showed HPV type 51. No relation was found between HPV infection and tumor subtype or prognosis, neither for HPV DNA positivity between serum and tissue. Conclusions: Our data support the feasibility of HPV DNA detection by liquid biopsy in BC. The presence of circulating HPV could be due to a viral spread from other organs. More data are needed to establish the role of circulating HPV DNA and its potential association with HPV infection of the breast and/or of the cervix. [Table: see text]