Do non-specific minimal signs in a biennial mammographic breast cancer screening programme need further diagnostic assessment?

Mammographic features such as small vague densities, indefinable microcalcifications, subtle architectural distortions, alone or in combination, are non-specific appearances for breast cancer. These features sometimes precede malignancy and a decisive strategy on how to deal with non-specific minimal signs in a breast cancer screening programme is therefore desirable. After studying the prevalence of these signs in a Dutch Breast Cancer Screening Centre and estimating the risk of participants with these signs acquiring breast cancer within 2 years, we have developed such a strategy. Non-specific minimal signs were seen on the mammograms of 53 of 500 (10.6%) participants, aged 50-70 years, in this programme. After retrospective analysis of the mammograms of 254 patients with screen-detected or interval carcinoma, non-specific minimal signs were detected in 77 cases. Combining the incidence of breast cancer with the difference between the expected number of non-specific minimal signs in the screening programme and its actual occurrence in previous mammograms of patients with breast cancer, the risk of cancer in women with these signs, additional to that of screened women in general (additional risk), is calculated as being 0.5%. Invasive breast cancer in women with previously detected non-specific minimal signs demonstrated a favourable stage at diagnosis (axillary metastasis in 23% vs 37% in cancers without these previous signs, p < or = 0.05). Our strategy for follow-up in case of non-specific minimal signs remains unchanged because of the low additional risk and favourable staging, and is restricted to an invitation for the next screening round in 2 years time.