Steroid hormone receptors in breast tumours presenting during pregnancy or lactation.

Cytosol oestrogen receptor (ER) and progesterone receptor (PR) levels were measured in tumours from three patients with breast cancer during pregnancy and from three patients developing breast cancer while lactating. All lactating patients were ER-positive and two were PR-positive, whereas pregnant patients were uniformly ER-negative and PR-negative. Pregnant patients had a significantly shorter disease-free survival compared with matched nonpregnant women with breast cancer. Of five patients developing metastatic disease, one from the lactating group had a complete remission with chemotherapy and one had static disease with endocrine treatment, whereas all others had progressive disease despite a variety of treatments. Although numbers are too small to permit generalisation, these provisional data suggest that patients presenting with breast cancer during pregnancy may have mainly receptor-negative tumours, a short disease-free interval, and may be relatively resistant to treatment of metastatic disease. By comparison, patients with breast tumours during lactation have receptor-positive disease and metastases may respond to systemic therapy.