Axillary lymph node metastases associated with small invasive breast carcinomas

Over the past 20 years the proportion of invasive breast carcinomas measuring < or = 1 cm has increased progressively. Information regarding the effect of clinical and histologic characteristics on the frequency of lymph node metastases associated with small invasive breast carcinomas is limited.

A review of Surveillance, Epidemiology, and End Results data was performed using cases diagnosed between January 1988 through December 1993. A total of 12,950 patients with invasive breast carcinomas measuring < or = 1 cm undergoing a resection of the primary tumor and an axillary lymph node dissection were included in this study. The effect of clinical and histologic characteristics on the frequency of lymph node metastases was reviewed.

The frequency of lymph node metastases associated with T1a tumors was less than that observed from T1b tumors (9.6% vs. 14.3%; P < 0.001). Tumors with favorable histology (mucinous, papillary, and tubular carcinomas) had a lower frequency of lymph node metastases compared with all other histologic types (3.9% vs. 13.9%; P < 0.001). Increasing histologic grade was associated with an increased risk of lymph node metastases ranging from 7.8% in Grade 1 tumors to 21.0% in Grade 4 tumors (P < 0.001). Increasing patient age was associated with a progressively decreasing frequency of associated axillary lymph node metastases ranging from 22.6% in women age < 40 years to 10.2% in women age > or = 70 years (P < 0.001).

Cases in which an axillary lymph node dissection can be avoided are those with an associated frequency of lymph node metastases < or = 5%, including T1a and T1b mucinous and tubular carcinomas, T1a papillary carcinomas, and T1a Grade 1 carcinomas.