One of the most important predictors of survival in women with infiltrating breast cancer is the presence or absence of axillary lymph node metastases. The incidence of lymph node metastases in infiltrating breast carcinomas measuring 1 cm or less ranges from 0 to 27.1 percent. Saiz and associates questioned if lymph node dissection is necessary in infiltrating breast carcinomas measuring 0.5 cm or less.

All infiltrating breast carcinomas with axillary lymph node dissection diagnosed at one institution that measured 1.0 cm or less in greatest dimension macroscopically were reviewed. These carcinomas were then divided into two groups: tumors measuring 0.5 cm or less (T1a) and those measuring 0.6 to 1.0 cm (T1b). Both groups were evaluated for patient age, histologic type of tumor, modified Bloom-Richardson grade, estrogen and progesterone receptor status, ploidy, S-phase fraction and angiolymphatic vessel invasion to determine if any of these tests could be used as indicators for patients at risk for axillary lymph node metastases. The presence or absence of lymph node metastatic disease was also recorded.

The results indicated that infiltrating breast carcinomas measuring 0.5 cm or less showed no axillary lymph node metastases. Those measuring 0.6 to 1.0 cm showed a 12.9 percent incidence of lymph node metastases. The modified Bloom-Richardson grade was the only test that correlated with the presence of metastases.

This study demonstrates the importance of detecting breast carcinoma in its early stage. The T1a tumors appear to have histologic and flow cytometric characteristics similar to those of T1b tumors. This suggests that, if allowed to grow, these tumors may have a higher incidence of developing into T1b tumors and of metastasizing. Follow-up studies on patients with T1a tumors are necessary to determine the role of small tumor size in long-term prognosis.

The authors conclude that the size of the tumor appears to be the best predictor of lymph node metastases in patients with infiltrating breast carcinoma. Patients with breast carcinomas measuring 0.5 cm or less appear unlikely to have metastatic lymph node disease and; therefore, may not need lymph node dissection.