Different expression of thymidylate synthase in primary tumour and metastatic nodes in breast cancer patients.

BACKGROUND: To date an accurate evaluation of predictive markers in breast cancer is mainly conducted at the primary site, although the main goal of the adjuvant therapy is the control of micrometastases. Adjuvant therapy drugs need a high proliferative cell rate to be effective. The proliferating activity can be evaluated by the Ki-67 marker and even by thymidylate synthase (TS), a cell cycle enzyme present in proliferating cells. In this study the TS levels in primary tumours were compared to those of their metastases. PATIENTS AND METHODS: The TS expression and Ki-67 were evaluated by means of immunohistochemistry in 80 primary breast tumours (PTs) and in their matched axillary metastatic lymph-nodes (ALNs). RESULTS: In 16% of patients, malignant cells of involved nodes showed a lower TS expression than the PTs. In the same group, we also found a lower number of Ki-67 immunoreactive cells in lymph node metastases when compared with primary tumours. CONCLUSION: The group of patients with lower TS and Ki-67 expression in lymph node metastatic cells may be less sensitive to 5-fluorouracil and high dose methotrexate requiring them to be treated with other drug combinations