Frozen section evaluation of breast carcinoma sentinel lymph nodes: a retrospective review of 1,940 cases

Abstract

Many sentinel lymph node biopsies (SLNBs) are evaluated intraoperatively by frozen section, which may impact the need for further axillary dissection (AD). However, the need for AD in patients with small metastases has been recently called into question, meaning that frozen SLNB may be unnecessary. Furthermore, frozen section can compromise tissue for further study. At our institution, we grossly evaluate all SLNB and freeze half of the node. Here, we evaluate the frozen SLNB discrepancy rate using this method, focusing on cause of discrepancy and need for further surgery. We reviewed surgical pathology records for all breast cancer resections with frozen section of SLNB examined from 2003 to 2012. For cases with a frozen section discrepancy, we compiled clinicopathologic data. In total, 1,940 cases involved frozen section evaluation of SLNB. In 95 cases (4.9% of total cases, 23.8% of positive node cases), the SLNB was called negative on frozen but positive on final examination (false negatives). The majority of missed metastases are isolated tumor cells or micrometastases. A trend was observed toward fewer patients receiving completion AD after a discrepant frozen SLNB in the later years of the study. The protocol of freezing half of a SLNB is a reasonable method, with results similar to or better than other studies. The main adverse outcome is the need for separate AD; however, additional positive nodes are uncommon. The trend of fewer patients getting additional AD after a discrepant frozen SLNB suggests that clinicians may be using this information differently recently.

Fig. 1

Representative false-negative intraoperative frozen sentinel lymph node biopsy due to “tissue sampling.” In this representative case with negative frozen section diagnosis, the diagnosis was changed to positive after a metastasis was detected in the non-frozen half of the lymph node on H&E (a ×4, b ×20) and cytokeratin immunostain (c AE1/AE3 immunostain, ×20) (“tissue sampling” error)

Fig. 2

Representative false-negative intraoperative frozen sentinel lymph node biopsy due to “block sampling.” In this representative case with negative frozen section diagnosis (a H&E ×20), the diagnosis was changed to positive for isolated tumor cells (b H&E ×20) after tumor cells were found on the deeper level in the permanent section, confirmed as carcinoma by immunohistochemistry for cytokeratin (c AE1/AE3 immunostain, ×20) (“block sampling” error)

Fig. 3

Size classification of metastases after false-negative intraoperative frozen sentinel lymph node biopsy. The majority of the metastases seen on the permanent section of the sentinel lymph node biopsies, after a false-negative intraoperative frozen section, were either isolated tumor cells (27 %) or micrometastases (42 %), with 31 % macrometastases (>2 mm)

Fig. 4

Follow-up axillary dissection (AD) rates. These charts illustrate the trend toward decreased follow-up AD in the later portion of the study, with 53 % of patients with false-negative frozen SLNB undergoing follow-up AD between 2003 and 2008 and 27 % of these patients undergoing follow-up AD from 2009 to 2012