High sensitivity of touch imprint cytology in young patients with invasive lobular carcinoma of the breast.

Invasive lobular carcinoma (ILC) of the breast is a rare type of breast cancer. Metastatic ILC is difficult to identify in sentinel lymph nodes (SLNs) because of its low-grade cytomorphology and its tendency to resemble lymphocytes. Touch imprint cytology (TIC) is a rapid method for evaluating SLNs intraoperatively. We sought to evaluate this technique in the identification of SLN metastases in ILC. A total of 230 SLNs from 88 patients diagnosed with ILC were examined with TIC, and the results were compared with their histological diagnosis. We first confirmed some typical cytological features of SLN metastases in ILC such as a thick eosinophilic background and hyperplasia of small cell lacking adhesion. Further analysis showed that sensitivity of TIC was 60.5 % on per-node basis and 58.3 % on per-patient basis; specificity of TIC was 100 % on per-node basis and 100 % on per-patient basis. Interestingly, when we divided patients according to their ages, the sensitivity of TIC in patients younger than 50 years old greatly increased to 90.9 % on per-node basis and 85.7 % on per-patient basis, whereas the specificity remained 100 % on both per-node basis and per-patient basis. However, different tumor sizes did not clearly change the sensitivity of TIC compared to the overall sensitivity. Patients with tumor size bigger than 1 cm revealed a TIC sensitivity of 59.4 % on per-node basis and 55.0 % on per-patient basis. These results suggest that TIC can be used as a reliable method of detecting SLN metastasis only in young patients with ILC.