Detection of disseminated tumor cells (DTCs) in bone marrow is an independent prognostic factor in primary breast cancer. Here, we conducted a proof-of-principle study to evaluate whether this tumor cell spread occurs already in patients with ductal carcinoma in situ (DCIS). After preoperative screening by stereotactic core biopsy, 30 consecutive women with DCIS were included. Bone marrow aspirates, taken at the time of primary surgery, were subjected to DTC detection by a standardized immunoassay using the established monoclonal anti-cytokeratin antibodies A45-B/B3 and AE1/AE3. DTCs were detected in 4 of 19 cases of pure DCIS (21.1%) and in four of seven cases of DCIS with microinvasion (57.1%). After a median follow-up time of 22 months, two initially DTC-positive patients suffered from contralateral carcinoma and contralateral DCIS at months 12 and 30, respectively, whereas the remaining patients were relapse free. Thus, hematogenous tumor cell dissemination into bone marrow is an early event in breast cancer development.
