An evaluation of molecular markers for improved detection of breast cancer metastases in sentinel nodes.
OBJECTIVE
In patients with breast cancer (BC), the sentinel node (SN) is the first node in the axillary basin that receives the primary lymphatic flow and can be used to accurately assess the axillary nodal status without removal of the axillary contents. Currently, histology and/or immunohistochemistry are the routine methods of SN analysis. The primary objective of this study was to develop a reproducible reverse transcription (RT) PCR assay, with emphasis on achieving high specificity for accurate detection of BC micrometastases in the SN. To correct for the heterogeneity of BC cells, a multimarker approach was followed, with the further aim of improving the detection rate of the assay.


METHODS
In total, 73 markers were evaluated, of which 7 were breast epithelial markers and 66 were either cancer testis or tumour associated antigens. Twelve BC cell lines and 30 SNs (from 30 patients) were analysed using RT-PCR to determine the in vitro and in vivo detection rates for each of the markers. In addition, 20 axillary nodes obtained from a patient with brain death were used as controls to optimise the PCR cycle numbers for all the markers.


RESULTS
Of the 30 SNs, 37% (11/30) were positive on haematoxylin and eosin analysis. Extensive immunohistochemical (IHC) analyses of the haematoxylin and eosin negative nodes confirmed the presence of very small numbers of BC cells in an additional 40% (12/30) of SNs. Molecular analysis with the hMAM-A alone identified metastases in 70% (21/30) of SNs. Using MAGE-A3 in combination with hMAM-A identified metastases in 90% (27/30) of patients. Seven SNs (23%) were negative for micrometastases (with haematoxylin and eosin and IHC) but RT-PCR positive for either hMAM-A or MAGE-A3.


CONCLUSIONS
As IHC analysis resulted in a 77% detection rate compared with 37% for haematoxylin and eosin analysis, we consider that IHC is essential in order not to miss SN micrometastases. Molecular analysis with hMAM-A and MAGE-A3 allows detection of BC micrometastases with a 90% detection rate. However, the clinical value of histologically negative but RT-PCR positive SNs can only be determined with long term follow up.
Abdul-Rasool
S
S
Department of Human Biology, Division of Haematology, Faculty of Health Sciences, University of Cape Town, Groote Schuur Hospital and National Health Laboratory Services of South Africa, Cape Town, South Africa. srasool@cormack.uct.ac.za
Kidson
S H
SH
Panieri
E
E
Dent
D
D
Pillay
K
K
Hanekom
G S
GS
D001943:Breast Neoplasms / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D045744:Cell Line, Tumor; D016172:DNA Fingerprinting; D005069:Evaluation Studies as Topic; D005260:Female; D015870:Gene Expression; D005819:Genetic Markers; D006801:Humans; D007150:Immunohistochemistry; D008207:Lymphatic Metastasis; D009367:Neoplasm Staging; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D021701:Sentinel Lymph Node Biopsy
D005819:Genetic Markers