Axillary lymph node status is one of the most important prognostic variables for
breast cancer (BC). To investigate and understand the clinical, histopathological and
biological factors that affect prognosis in node-positive young
breast cancer patients, we compared the phenotype of 100 primary tumours with their corresponding loco-regional lymph node (LN)
metastases using conventional immunohistochemistry (IHC) markers currently in use for molecular classification of
breast cancer. By comparing the expression of ER, PR, HER-2, Ki67, K8, K5/6 and
vimentin, we found that expression of HER-2, Ki67, K8 and
vimentin is frequently lost in
lymph node metastases. Between the primary tumour and corresponding
lymph node metastases, expression of
keratins K8 and K5/6 significantly changed. Expression of K8 in
lymph node metastases, but not in primary tumours, segregates patients in two sub-groups with different outcomes. Survival of patients with K8-positive LN
metastases at 5 years in comparison with patients with K8-negative LN
metastases was 75 vs 48 %,
at 10 years 62 vs 22 % and at 20 years 53 vs 14 % (p < 0.001). K8 immunostaining of tissue from the
lymph node metastasis allows defining a sub-group of lymph node-positive BC patients with a highly unfavourable outcome, for whom therapeutic options might have to be reconsidered.