The subcutaneous reaction: a useful mammographic sign.

The appearance of a subcutaneous reaction which may be observed on a mammogram in the presence of underlying pathology is described. When this sign was used as the sole indicator of malignancy in a series of 273 consecutive biopsied cases, a specificity of 96% and a positive predictive value of 89% was observed. Non-malignant cases, not in the series, are also presented and it is concluded that, in cases not investigated by Tru-cut needle biopsy or cyst aspiration and in the absence of infection or lymphoedema, malignancy should be considered a highly likely cause of a subcutaneous reaction.