Infiltrating micropapillary carcinoma of the breast

Infiltrating micropapillary carcinoma of the breast is a recently described and poorly recognized aggressive variant of infiltrating ductal carcinoma for which the clinical significance and role of prognostic markers are not fully described. In 14 cases of infiltrating micropapillary carcinoma, we s tudied histologic characteristics; immunohistochemical expression of c-erbB -2, p53, and MIB-1; hormonal expression of these tumors; and genetic altera tions on the p53 locus. We correlated these results with clinical outcome. Patient ages ranged from 37 to 58 years (mean, 50 yr). Nine patients presen ted with a palpable tumor, one with an axillary mass. Three patients had ab normal mammograms. Five patients (36%) presented with Stage II disease, eig ht (57%) with Stage III, and one (7%) with Stage IV. The tumors were a modi fied Bloom-Richardson Grade II in nine cases (64%) and Grade III in 5 (36%) . Mitoses ranged from 1 to 12 per 10 high power fields. Necrosis was unifor mly absent. Psammoma bodies were present in 9 cases (64%) and lymphatic inv asion in 10 (71%). In all of the cases, c-erbB-2 was identified immunohisto chemically, and MIB-1 was positive, staining 30 to 60% of the tumor cells. The cells were immunoreactive for p53 in six (75%) of eight cases, and, whe n present, stained 20 to 50% of the tumor cells. Loss of heterozygosity on locus 17p13.1 (p53) was identified in 4 of 5 informative samples. Molecular and immunohistochemical analyses had an 80% concordance. Follow-up was ava ilable in 11 patients, of whom 9 had recurrence in the skin and chest wall (average time of recurrence, 24 mo). Recognition of this distinctive and ag gressive variant of infiltrating carcinoma is important because of its unfa vorable prognosis and specific pattern of local recurrence. Its aggressive nature is supported by its advanced stage at presentation and expression of unfavorable prognostic markers.