Recent studies have shown that an increased number of axillary lymph node metastases is associated with non-visualized lymph nodes. The purpose of the study was to retrospectively analyze the incidence and characteristics of non-visualized sentinel lymph nodes (SLNs) in nodal metastases in breast cancer patients.

Consecutive women with breast cancer referred for lymphoscintigraphy from January 2021 to November 2022 were reviewed retrospectively. Findings from resected SLNs and non-SLNs and relevant histopathology were collected and analyzed.

500 patients diagnosed with breast cancer were reviewed, excluding 93 patients due to neoadjuvant therapy, DCIS, recurrence, or incomplete clinical documentation. Of the 407 remaining patients, 108 patients were positive for axillary lymph node metastases (24 %) and were the focus of the study. Of this patient cohort, 38 patients (35 %) had non-detected SLNs by intraoperative gamma probe and 43 (40 %) had non-visualized SLNs by lymphoscintigraphy. There was statistically significant difference in primary tumor size (39.8 mm versus 28.9 mm), number of resected (6.9 ± 4.4 versus 4.6 ± 2.4) and positive (3.4 ± 2.2 versus 1.6 ± 1.3) lymph nodes, size (13.8 ± 6.1 mm versus 8.1 ± 4.5 mm), tumor grade and tumor stage between the SLN non-visualized and visualized groups. The multivariate logistic regression analysis showed that only lymph node size and number of lymph nodes resected were independent factors associated with SLN non-visualization.

We reported a high non-visualization rate of SLN in breast cancer patients with pathology-proven positive axillary nodes. The causes of the SLN non-visualization are not well understood and warrants further exploration.