Background: The presence or absence of regional lymph node metastases has been one of the most important determining factors in recommending adjuvant chemotherapy for patients with breast carcinoma. However, because of the 15-20% failure rate at 5 years for lymph node negative patients, other tumor-related prognostic factors have gained greater significance in this decision-making process. Many investigators have reported finding micrometastases that were not detected by routine sectioning of the lymph nodes but were identified by multiple sectioning and additional staining. This review attempts to evaluate the role of occult lymph node micrometastases and their relevance to disease recurrence.
Methods: A literature search of the entire MEDLINE data base was conducted. All relevant articles were reviewed for the criteria they used to define micrometastases. The frequency of detection of micrometastases by various methodologies and the prognostic significance of such deposits were examined.
Results: Tumor deposits involving the lymph nodes were found to be arbitrarily categorized as either micrometastases or macrometastases, with the cutoff point ranging from 0.2-2.0 mm. The detection rate of such deposits by conventional techniques was inadequate. Serial sectioning and immunohistochemistry appeared to increase the detection rate by 9-33%. A definite survival disadvantage was noted for patients with such occult metastases.
Conclusions: Current routine histologic examination of regional lymph nodes underestimates breast carcinoma metastases. Serial sectioning and immunohistochemistry increase the yield but are too labor-intensive and expensive for routine use. However, the introduction of the sentinel lymph node biopsy in lieu of axillary lymph node dissection in cases of breast carcinoma holds promise for making these methods practical and cost-effective.