Background: Thirty percent of lymph node negative patients with operable breast carcinoma experience disease recurrence within 10 years. Retrospective serial sectioning of axillary lymph nodes has revealed undetected metastases in 9-30% of these patients. These occult metastases have been shown to have an adverse effect on survival. Serial sectioning (SS) is impractical for all axillary lymph nodes harvested from Levels I and II, but it is feasible if applied only to sentinel lymph nodes.
Methods: Sentinel lymph nodes from 52 patients with invasive breast carcinoma were cut at 2 mm intervals, fixed in 10% formalin, and embedded in paraffin. Sections were taken from the blocks, stained with hematoxylin and eosin (H & E), and compared with cytokeratin-stained sections taken at 0.25 mm intervals throughout the entire blocks.
Results: Tumor metastases were found in 6 patients (12%) when the sentinel lymph nodes were sectioned at 2 mm intervals and stained with H & E, compared with 30 patients (58%) when the same lymph nodes were serially sectioned at 0.25 mm intervals and stained with cytokeratin. Of 24 patients whose metastases were detected by SS and cytokeratin staining, 12 had isolated tumor cells and 12 had colonies of several thousand malignant cells.
Conclusions: Routine histologic examination of axillary lymph nodes, including sentinel lymph nodes, in cases of breast carcinoma significantly underestimates lymph node metastases. This deficiency may be overcome by SS of the entire lymph nodes and staining with a specific monoclonal antibody. The percentage of patients found to have colonies of cells that were missed by routine sectioning corresponds closely to the percentage of "lymph node negative" patients who would be expected to relapse. The true clinical significance of these occult metastases will be determined by long term follow-up. [See editorial on pages 905-7, this issue.]
Copyright 1999 American Cancer Society.