No clinical relevance of cytokeratin positive cells in bone marrow of patients with primary breast cancer

Background: Bone marrow samples from 2017 patients operated for primary breast cancer (stage T1–4, N0/N+, M0) at the University Hospital Heidelberg between 1999 und 2005 were analysed for disseminated tumor cells (DTC) on cytospin slides using cytokeratin (CK) specific antibodies and the APAAP and SA-AP detection systems.

Material and Methods: DTC were stained using CK antibodies 5D3 and A45. Slides were analysed by automated picture analysis with the ACIS II system (ChromaVision). Criteria for classification of disseminated tumor cells were in compliance with the publication of Fehm et al. (Cancer, Vol.107, 2006).

Results: Small cells characterized by an excentrically located small and clear nucleus were detected in 56% of the bone marrow samples. These cytokeratin-positive normal bone marrow cells are characterized by a mean area value of 102 (area=cell size x staining intensitiy). In contrast, tumor cells were characterized by strong and irregular cytoplasmic cytokeratin staining, a granular nucleus and a clearly enlarged nuclear size. These DTC had a mean value for the parameter area of 309 according to the ACIS picture analysis. Using these tumor classification critera 26 (1.3%) from 2017 patients with primary breast carcinoma were scored DTC positive.

Discussion: We have shown that bone marrow stroma cells are positive for various epithelial antigens including CK. Elimination of these cells either by size exclusion in picture analysis or by immunomagnetic separation results in tumor cell detection rates of less than 2% in 2×10⁶ bone marrow cells. We conclude that cytological DTC analysis has no clinical relevance in patients with primary breast cancer stage T1–4, N0/N+,M0.

disseminated tumor cells - standard immunocytology