Imprint cytology of axillary lymph nodes as an intraoperative diagnostic tool

Frozen section histology of lymph nodes intraoperatively is associated with a false negative rate of twenty-five per cent. Imprint cytology is reported to have greater accuracy than frozen section. Accurate intraoperative examination of lymph nodes could help to prevent some patients from having a second axillary operation in breast cancer. This study assesses the sensitivity of imprint cytology to lymph node metastases using two different staining techniques.

Imprint cytology of 238 freshly excised axillary lymph nodes in 53 patients with stage T1-2, N0, M0 breast cancer was performed. Imprints were stained using toluidine blue dye and anti-pancytokeratin immunoglobulin to compare the two staining methods. A consultant histopathologist blinded to the routine histology results examined each set of imprints. A non-pathologist also examined each set of imprints to determine whether a technician could be used to screen slides in order to decrease the workload of the pathologist.

Sensitivity was 82% with toluidine blue and 36.4% with anti-pancytokeratin immunoglobulin. Positive predictive values were 100% and 57% respectively for toluidine blue and anti-pancytokeratin. The false-negative rate was 18% for toluidine blue and 63.6% for anti-pancytokeratin antibody when examined by a consultant histopathologist.

Imprint cytology using toluidine blue is as sensitive as frozen section in the detection of axillary lymph node metastases. A positive result may be acted upon with acceptable safety. Immunohistochemistry using antibody to pancytokeratin did not improve imprint sensitivity in this study. Imprint cytology could help to prevent a second operation in 80% of breast cancer patients with positive lymph nodes.