Update on Sentinel Lymph Node Methods and Pathology in Breast Cancer

Abstract

Breast cancer stands out as the most commonly diagnosed cancer among women globally. Precise lymph node staging holds critical significance for both predicting outcomes in early-stage disease and formulating effective treatment strategies to control regional disease progression in breast cancer patients. No imaging technique possesses sufficient accuracy to identify lymph node metastases in the early stages (I or II) of primary breast cancer. However, the sentinel node procedure emerges as a valuable approach for identifying metastatic axillary nodes. The sentinel lymph node is the hypothetical first lymph node or group of nodes draining a cancer. In case of established cancerous dissemination, it is postulated that the sentinel lymph nodes are the target organs primarily reached by metastasizing cancer cells from the tumor. The utilization of the sentinel node technique has brought about changes in the assessment of lymph nodes. It involves evaluating the sentinel node during surgery, enabling prompt lymph node dissection when the sentinel node procedure is positive. Additionally, histological ultra-stratification is employed to uncover occult metastases. This review aims to provide an update of this valuable technique, with focus on the practical aspects of the procedure and the different histological protocols of sentinel node evaluation in breast cancer.

Keywords: intraoperative pathology; preoperative detection; sentinel lymph node.

Figure 1

Bilateral breast invasive ductal carcinoma: lymphoscintigraphy after 24 h of injection of 99mTc-albumin nano-colloid: (A) planar acquisition; (B) SPECT-CT highlighting lymph node 1 of the right side; (C) SPECT-CT highlighting lymph node 2 of the right side; (D) SPECT-CT highlighting the only lymph node of the left side.

Figure 2

Macroscopic intraoperative SLN process. (A) Fresh intraoperative SLN. (B) Bivalvular section along the longest axis. (C) Slices of LN on a glass slide. (D) Unstained transferring cells. (E) Stained imprint. (F) Frozen slice in a cryostat. (G) Stained frozen slide.

Figure 3

Metastatic sentinel lymph node imprint (rapid H&E), ×100. 🠮 Atypical epithelial cells. ↙ Macrophage. ⇊ Normal LN cells.

Figure 4

Lymph node with lobular carcinoma, stained with cytokeratin AE1/AE3 in immunohistochemistry, ×100. ★ Normal LN tissue. ⮘ Metastatic stained cells (brown chromogen).