Touch imprint cytology evaluation of sentinel lymph node in breast cancer

Most centers use lymphoscintiscan for identification of a sentinel lymph node (SLN) and frozen section for its evaluation. The aim of the present study was to assess the accuracy of peritumoral methylene blue dye injection for SLN identification and the technique of touch imprint cytology (TIC) for its evaluation.

One hundred and eight fine needle aspiration cytology (FNAC)-proven breast cancer patients with clinically N0 axilla were recruited for the study. Prior to the induction of anesthesia, 5 ml of 1% methylene blue was injected in the peritumoral region to stain the sentinel node, following which conventional modified radical mastectomy was performed. Touch imprint cytology was obtained from the cut surface of the SLN, and then the SLN along with all nonsentinel nodes were sent for histopathology.

Intraoperative identification of a blue node was possible in 102 of 108 patients (94%). Touch imprint cytology had a sensitivity of 88%, specificity of 98%, and overall diagnostic accuracy of 94% for diagnosing metastasis in the SLN. The false positive rate for malignancy of TIC versus histology was 2.5% and the false negative rate 7.8%.

Blue dye lymphatic mapping by peritumoral injection of methylene blue was found to be accurate and cost effective for SLN identification. It avoids the expenses of lymphoscintiscanning, which requires special infrastructure and expertise with a significant learning curve. The identified SLN can, with reasonable accuracy, be assessed for metastasis by TIC. The frequently used method of frozen section requires a cryostat and a pathologist trained in the technique. Additionally scanty SLN tissue can be wasted in the cryostat and freezing artifacts can be introduced in the imprint, both of which are avoided by TIC.