Sentinel lymph node molecular pathology in breast carcinoma

The prognosis of breast cancer patients depends on primary tumor resection and axillary lymph nodes examination. The purpose of this study was to analyze by molecular biology techniques the presence of mammaglobin A and B messenger RNA in breast sentinel lymph node (SLN) by reverse-transcription polymerase chain reaction (RT-PCR).

Sentinel lymph nodes from 50 patients with a diagnosis of breast cancer were prospectively studied between June 2004 and August 2006. Lymph nodes were all examined every 2 mm by intraoperative cytology. Hematoxylin-eosin (HE), immunohistochemistry (IHC) with cytokeratin (clone AE1-AE3, DAKO, dilution 1:100), and molecular biology techniques were used in all cases.

Deferred study with routine techniques showed subcapsular metastasis in 3/50 cases. Out of 50 cases, 5 were detected with IHC, and 2 of them were negative for HE. Multiplex RT-PCR allowed the detection of 18/50 positive SLN, which included the 5 above-mentioned cases. The other SLN studied (32/50) showed no metastases with the methods herein implemented.

The epidemiologic impact of incomplete SLN study has been observed, as the HE technique fails to identify all SLN with micrometastases. In our opinion, SLN should be studied with IHC and molecular biology techniques. The multiplex RT-PCR technique for A and B mammaglobin proves to be specific and sensitive. This study will serve to formulate hypotheses. Further research, including a larger population and a longer-term follow-up period, will be required to confirm these hypotheses. Should our findings be confirmed in the future, molecular biology determinations could modify patients' staging and treatment.