Metastasis risk assessment in breast cancer (BC): a preliminary study of pre-metastatic niche (PMN) in nonmetastatic nodes

Bone marrow-derived hematopoietic progenitor cells (HPCs) seem to participate in early spread of cancer cells by forming a peculiar and highly organized microenvironment called PMN. Identifying such HPCs in the PMNs is emerging as a key step in assessing risk of metastasis. In this preliminary study we analysed 294 axillar nodes (271 pN0 and 23 pN1a) obtained from 30 pts undergone surgery for breast ductal invasive carcinoma in the period 1998-2000. Pts mean age was 61.2 years (range 45-79); 9 pts (30%) were premenopausal and 21 (70%) postmenopausal; 13 pts (43.3%) had ER+, 10 (33.3%) PR+; MIB1 was £ 25% in 22 pts (73.3%), >25% in 6 (20%), unknown in 2 pts. After a median follow-up of 81.27 mos (range 12–136), 14 pts are disease-free, 9 pts dead of metastatic disease. Involved sites were: 1 loco-regional, 7 bone, 3 lung, 4 liver, 1 brain. Samples were fixed in 10% neutral buffered formalin for 12-72 hrs and included in paraffin at 56C; 4 ml thick sections were pre-treated in microwave owen in 10 mM citric acid, pH 6.0 and incubated overnight with the following poly/mono-clonal antisera: VEGF-R1 (Santa Cruz Biothechnology 1:400),CD 133(Abgent 1:80),CD 117 (DAKO 1:500),CD-34 (DAKO 1:50). Clusters of immunoreactive cells were evident with CD 117 and CD 34 in all nodes. A different degree of immunopositivity was found with VEGR-R1 and CD 133 antibodies for different sites of metastasis; in particular, the cases spread in lungs, liver and central nervous system were more immunoreactive, compared to those with bone localization. All nodes classified as pN1a showed no immunoreactivity. The prognostic significance of HPCs in PMN needs to be further investigated, especially in node-negative BCs. The immunomorphologic aspect of the lymph node microenvironment could have significant clinical implications, in order to optimize BC therapeutic strategies