Histologic grade of locally advanced infiltrating ductal carcinoma after treatment with induction chemotherapy.

Multiagent chemotherapy is often used to treat patients with locally advanced infiltrating breast carcinoma before mastectomy. One of the most important prognostic factors, histologic grade, may be altered by induction chemotherapy. Because locally advanced infiltrating breast carcinomas are frequently diagnosed by fine-needle aspiration, histologic grade can be determined in the mastectomy specimens only after chemotherapy. Histologic grade, with its three components, was examined in 30 mastectomy specimens after induction chemotherapy for infiltrating ductal carcinoma and compared with findings in available pretreatment incisional biopsy specimens. Histologic grade for the 24 axillary lymph node-positive carcinomas treated with induction chemotherapy was compared with the grade for 24 axillary lymph node-positive ductal cancers that had been treated by surgery only. Complete, partial, or no clinical response was seen in 4 (13%), 21 (70%), and 5 (17%) patients after chemotherapy. In six of seven tumors, there was complete agreement between biopsy and postchemotherapy mastectomy specimens in grade and in scores for the three components. Half of the 24 node-positive tumors from patients treated with chemotherapy and 21% of node-positive neoplasms from patients treated initially with surgery had a mitotic count score of 1. In these two node-positive groups, 71% of tumors from patients treated with surgery and 92% of cancers from patients treated with induction chemotherapy showed a nuclear pleomorphism score of 3. For these two groups, however, there were no statistically significant differences in histologic grade or in any of its three components.