The authors report an unusual case of extensive placental micrometastases of breast carcinoma occurring in a 43 years-old woman, seen at 31 weeks gestation with metastatic disease. A female infant was delivered by caesarean section. Physical examination of the newborn was normal. The mother rapidly died of metastatic disease. Placental metastases from maternal tumours are rarely reported in the literature. The diagnosis is made by histologic examination. Placental metastases are associated with bad prognosis for the mother. The foetus is usually free of tumours when the metastases are limited to the intervillous space.