Specimens obtained from 92 patients with invasive ductal carcinoma of the breast by quadrantectomy and axillary lymph node dissection were examined to evaluate the relationship between existence of lymphatic invasion in peritumoral breast tissue and presence of axillary lymph node metastasis. The number of lymphatic invasions was classified into 4 groups (ly0-3) by counting the number of peritumoral lymphatic invasions. In addition, immunohistochemistry for cytokeratin was performed to locate micrometastasis in the dissected lymph nodes. Thirty-seven (40.2%) of 92 cases had foci of lymphatic invasion and 29 (31.5%) cases revealed lymph node metastasis on initial routine examination. The rate of diagnosis of lymph node metastasis assessed by the existence of lymphatic invasion had an accuracy of 84.8%, a sensitivity of 89.7% and a specificity of 82.5%. On the other hand, all 3 cases (4.8%) with micrometastasis detected by immunohistochemistry for cytokeratin, showed lymphatic invasion. The rate of diagnosis after detection of micrometastasis increased and exhibited 88.0% accuracy. In addition, the rate of prediction of lymph node metastasis in cases with tumor larger than 15 mm was also high, and its accuracy was 88.2%. These results suggest that the assessment of peritumoral lymphatic invasion is very useful for predicting the presence of axillary lymph node metastasis including micrometastasis. They also suggest that excision specimens should be examined for lymphatic invasion, and that the results of the examination might be necessary to pick up false-negative cases and those at high risk for lymph node metastasis among patients who have not undergone lymph node dissection based on the result of sentinel lymph node biopsy.

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