Detection of micrometastases in lymph nodes from patients with breast cancer

Background: Sentinel node biopsy affords the opportunity of focused examination of lymph nodes, including the use of the reverse transcriptase-polymerase chain reaction (RT-PCR). The mammaglobin gene is expressed by breast cancers but has not been detected in histologically normal lymph nodes. This study compared mammaglobin RT-PCR with routine histology in the sentinel and non-sentinel nodes of patients with breast cancer. Methods: Patients with breast cancer underwent tumour excision, sentinel node biopsy and axillary dissection. All nodes were bisected and half of each node was sent for routine histological examination. The other half underwent RNA extraction and mammaglobin RT-PCR. Results: Sentinel node biopsy was successful in 50 (96 per cent) of 52 patients. Mammaglobin expression was detected in nine (8 per cent) of 119 histologically negative sentinel nodes (Clopper-Pearson 95 per cent confidence interval (ci.) 4 to 14 per cent) and in 13 (5 per cent) of 247 histologically negative non-sentinel nodes (95 per cent c.i. 3 to 9 per cent). Mammaglobin expression was detected in four (13 per cent) of 31 patients with histologically negative sentinel nodes (95 per cent c.i. 4 to 30 per cent) and in six (14 per cent) of 44 patients with histologically negative non-sentinel nodes (95 per cent c.i. 5 to 27 per cent). The false-negative rate for sentinel node biopsy was zero using histology results and 10 per cent using RT-PCR. Conclusion: RT-PCR screening of axillary nodes for mammaglobin expression increased the detection of breast cancer metastases compared with routine histology.