Characteristics and treatment of breast cancers 10 mm or less detected by a mammographic screening programme

Small invasive breast cancers up to 10 mm in size have an excellent prognosis and are being detected in increasing numbers by mammographic screening, yet optimal treatment remains controversial.

A review was made of pathology and treatment data relating to 100 consecutive invasive breast cancers up to 10 mm in size detected among 52,126 women who were screened over a 32-month period.

The most common radiological finding was a stellate lesion (44%). Thirty-three cases had an extensive in situ component in addition to the invasive tumour, and included among these were seven ductal carcinoma in situ (DCIS) cases with microinvasion. Of 79 patients who had axillary dissections, seven (9%) were node-positive. Tumours < or = 5 mm were as likely to be node-positive (11%) as those 6-10 mm in size (8%). Positive nodes were found only in patients with more than five nodes excised. Breast conservation surgery was performed in 84% of patients treated by surgeons associated with the programme, and 63% of patients were treated by other surgeons (P = 0.054, exact test). Breast radiation after breast conservation surgery was used in 44% of the cases, but was almost twice as likely to be used if the tumours were > 5 mm (51%) than if the tumours were < or = 5 mm (29%). Adjuvant tamoxifen was given to 61% of the cases.

We found that small invasive breast cancers are commonly treated by breast conservation, which usually includes axillary dissection. Even the smallest may be node-positive, and there is uncertainty about the place of adjuvant radiation therapy and tamoxifen.