**2. Patient data obtained for analysis**

Mammograms were retrieved of all tumours of pathological size less than 15 mm, diagnosed in women aged 40-69 between 1977 and 1998 in Falun Central Hospital, Sweden. Of these, 425 were identified to have stellate appearance and either no calcifications or nonspecific calcifications on the mammogram. Patient charts were retrieved and additional pathological information was obtained on exact tumor size in mm, node status, tumor grade and histological type. Treatment details with respect to surgery, adjuvant radiotherapy, chemotherapy and hormonal therapy were also retrieved. In addition, we recorded age, date of diagnosis, mode of detection (screening or symptomatic) and follow-up details including dates of local recurrence, death from breast cancer and death from other causes.

There was an average follow-up of 10.4 years to recurrence, death or last known date alive and disease-free, and a maximum follow-up of 27.9 years. The most recent date of follow-up was 20th March 2006. Local recurrence was defined as the occurrence of a histologically confirmed *in situ* or invasive carcinoma in the ipsilateral breast after treatment of the first breast cancer was completed.
