This retrospective single-institution study was designed to describe the main clinical, radiological and histological features, as well as the outcome of pregnancy-associated breast cancer (PABC), with a special emphasis on imaging and diagnostic difficulties.

We reviewed all breast cancers diagnosed during pregnancy or during the 12 months following delivery at our institution, between 1993 and 2009. Out of a total of 16,555 new cases of breast cancer observed during this period, 117 PABC (0.7%) were diagnosed.

Mean age at diagnosis was 33.7 years. Most cancers (81.2%) were diagnosed after delivery. Intermediate or high family risk was frequent (27.5%). The most common mode of presentation was a palpable mass (89.7%). Mean time to diagnosis was 5.8 months. Sensitivity for mammography was 80.9% and for ultrasound 77%. Most prognostic factors were unfavourable: frequent lymph node involvement (51.8%), high-grade tumours, hormone receptor negativity (45.9%) and HER2 positivity (38.7%). Treatments generally included surgery (61.7% mastectomies), radiotherapy (96%) and chemotherapy (79.6%). Overall 5-year survival was 81.8%.

PABC is an uncommon but aggressive form of breast cancer and must be considered in the presence of any breast abnormality during pregnancy or the months following delivery. Mammography and ultrasound should both be performed at the slightest clinical suspicion. Radiologists must be aware that masses may lack typical malignant ultrasound characteristics. Biopsies should be largely performed.