While serological evidence for HCMV in breast cancer may be limited, a stronger case is made by studies that have detected viral DNA and proteins by PCR and immunohistochemistry (IHC) in tumor biopsy specimens. In Taiwan, analysis of 62 breast cancer patients found that detection of both HHV-8 and HCMV in tumor samples by PCR was associated with lower overall survival and a decrease in relapse-free time . Harkins et al. detected HCMV immediate early (IE) proteins by IHC in breast glandular epithelial cells in 31 of 32 specimens from patients with ductal carcinoma in situ (DCIS) or infiltrating ductal carcinoma (IDC) . Another study found both HCMV IE and late proteins expressed in metastatic tumor cells in 100% of breast cancer specimens analyzed (73 total), and viral DNA was detected in 12/12 samples tested . Detection of virus in breast epithelial cells is consistent with the notion that epithelial cells are a site of HCMV persistence , and further supported by the fact that transmission of infectious virus through breast milk is well-documented [16–19].