Metaplastic breast cancer: clinical significance

Metaplastic breast carcinoma (MBC) is a rare poorly differentiated breast cancer characterized by coexistence of ductal carcinoma with areas of matrix producing, spindle-cell, sarcomatous, or squamous differentiation; ER/PR/HER2 negativity; and a reputation for poor outcome.

The Swedish Cancer Institute prospective breast cancer database (> 6500 patients; 1990-2005) has 24 MBC cases that were compared with typical breast cancer cases matched for age, date of diagnosis, stage, and ER/PR/HER2 status.

The mean metaplastic primary tumor diameter was 2.5 cm. The histological/nuclear grade was high in 21 of 24 cases. No patient had distant metastasis. ER and/or PR receptor status was negative in all cases. HER2 was negative in 10 of 11 cases tested. EGFR (HER1) was positive in 7 of 7 cases tested. All patients had sentinel and/or axillary lymph node dissection and surgical resection; 18 received chemotherapy and 22 had radiation therapy. Four patients had distant recurrences 5 to 88 months from diagnosis. Five-year survival was 83% (95% confidence interval, 66-100%). Comparison with matched typical breast cancer cases revealed no major significant difference in multidisciplinary treatment patterns, recurrence, or survival.

MBC is associated with poor prognostic indicators, but outcomes comparable with matched typical breast cancer cases can be achieved with routine aggressive multidisciplinary care. Increased, expression of EGFR (HER1) provides an opportunity for targeted tumor therapy.