Intra-operative touch imprint cytology for assessing sentinel lymph nodes in patients with lobular breast cancer

Abstract #1008 Background: Touch imprint cytology (TIC) as a tool for intra-operative assessment of sentinel lymph nodes (SLN) in breast cancer has been shown to be rapid, reliable and cost-effective. Its use in lobular cancer is however more challenging due to the pattern of lymph node infiltration, smaller cells, similarity to lymphocytes and low grade cytomorphology. The aim of this study was to evaluate the sensitivity and specificity of intra-operative TIC in assessing SLN metastases in patients with lobular breast cancer. Material and Methods: All patients with lobular carcinoma who underwent intra-operative TIC assessment of the SLN were identified within our prospectively collected database. The SLN was bi-valved along its longitudinal axis and imprinted onto a slide at least six times before air-drying. The slide was treated with the rapid Giemsa stain before examination by one of three cytopathologists. Where TIC revealed SLN metastases, the patient underwent immediate axillary clearance. The SLN were then processed for histopathology by sectioning at three levels before haematoxylin and eosin staining. Those lymph nodes found to be negative then underwent immunocytohistochemistry staining before being declared truly negative. All patients with SLN metastases not identified during surgery received a delayed axillary clearance. The TIC results were compared to the final histopathology result of the SLN and the sensitivity and specificity calculated. Results: 51 patients with lobular cancer who underwent TIC were identified. The table below summarises the results: The sensitivity thus calculated was 76.0%; the specificity 100.0% and the negative predictive value 81.25%. Of the 6 false negative cases, 4 were grade 1 and 2 were grade 2. The mean primary tumour size in this group was 17mm (range 11 to 27mm). In all 6 cases, axillary metastases was found in 3 or fewer lymph nodes post axillary clearance. Discussion: This study demonstrates the reliability of using intra-operative TIC to evaluate SLN during surgery for lobular cancer. It compares very favourably to data published in the literature from other institutions that have examined the use of TIC in lobular carcinoma and may relate to the presence of experienced, highly motivated cytopathologists at our unit. In addition, it also compares well with other studies describing the use of TIC in ductal carcinoma, including our own unit's previously published data. Thus, in experienced hands, TI