Objective. To evaluate the efficiency and safety of sentinel lymph node biopsy (SLNB) in patients with breast cancer with complete response to neoadjuvant chemotherapy (NAC). Methods. Ninety-two consecutive (T1-4 and N1-2) patients with breast cancer who had pathologic and/or clinical and radiologic axillary lymph node involvement were included. All patients received NAC. Patients with a clinical and radiologic complete response in the axilla after NAC underwent SLNB. Pathologic complete response (ypCR) was defined as the absence of residual invasive and in situ cancer, and near-complete response (ypNCR) represented in situ and/or ≤ 1 mm residual tumor in the breast and/or presence of malignant cell clusters (≤0.2 mm) and/or micrometastases (≤2.0 mm) in the axillary lymph nodes (ALN) (ypTis/T1mi, ypN0i+/pN1mi). Results. The mean age of the 92 patients was 49.6 ± 10.3 years and the mean follow-up was 34.0 ± 17.8 months. With respect to breast tumors, 23 (25.0%) patients had complete and 14 (15.2%) had a near-complete response to NAC. Complete response in ALN was obtained in 39 (42.4%) patients and near-complete in six (6.5%) patients. The overall survival of the 33 patients who achieved ypCR and ypNCR was 100% and the remaining 59 patients with partial or no response to NAC was 83.1% at a mean follow-up of 34 months ( p = 0.063 ). Conclusions. In this study, no event developed in cases with ypCR and ypNCR in the breast and axilla. The persistence of the same results in long-termfollow-ups may enable the use of ypNCR as a positive prognostic marker in addition to ypCR.

The histopathological findings are similar in invasive lobular carcinoma of the breast and poorly cohesive carcinoma of the stomach. Therefore, the possibility of metastasis should be kept in mind in multiple erosions or linitis plastica type gastric lesions. •In breast cancer patients who develop gastrointestinal tract metastases, determining the nature of the tumor (primary or metastatic) is extremely important in terms of treatment. •The importance of histopathological examination is critical and is highlighted in this report.• Possible diagnostic errors can be avoided by making immunophenotypic evaluation of endoscopic biopsy material with an appropriate immunohistochemical panel.

PURPOSE: To investigate the frequency, clinical significance, and causes of molecular discordances between tru-cut biopsy and residual tumor in patients with breast cancer who received neoadjuvant chemotherapy (NACTx). METHODS: Estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) statuses; hormone expression levels; Ki-67 index; and tumor grade in tru-cut biopsy before NACTx and in the residual tumor after NACTx were evaluated and compared using the Wilcoxon signed-rank test.RESULTS: The study included 102 women. Histopathologically, approximately 70% of the patients were partially responsive and 30% were unresponsive. The concordance and discordance rates between tru-cut biopsy and residual tumor were 95.1% vs. 4.9% (p = 0.180) for ER, 97.1% vs. 2.9% (p = 0.083) for PR, and 89.2% vs. 10.8% (p = 0.763) for HER2. Following NACTx, 15% of hormone receptor (HR)-negative patients and 5.7% of HER2(−) patients became positive, requiring adjuvant treatment. In particular, 18% of triple-negative patients became HR(+) and 12% became HER2(+). HER2 loss was detected in 40% HER2(+) patients. Ki-67 and PR expression significantly decreased in pathologically responsive patients (p = 0.001 and p = 0.004) and tumor grade increased in pathologically unresponsive patients (p = 0.034).CONCLUSION: NACTx alone cannot explain receptor discordance observed in breast cancers. HER2 loss and decreased PR expression levels are mainly associated with NACTx; whereas the receptor status turning positive, which has clinical significance for adjuvant treatment, is primarily associated with intratumoral heterogeneity. Therefore, immunohistochemical re-staining for biomarkers should be performed in residual tumors.