[An analysis of 136 groups of microcalcification of benign origin. How specific is the "triangle principle" (author's...

Amongst 107 localised groups of microcalcification of benign origin and not intraductal in localisation, there were 79 which showed round, oval or amorphous configuration, and 28 which were triangular. Of 29 intraductal areas of microcalcification, 26 showed appearances resembling an intraduct carcinoma. The "triangle principle" is therefore specific for the intraductal location of the lesion, but is unrelated to the question of malignancy. If the shape of the lesion had been used as the sole indication for biopsy, ie. had one operated only on those groups of microcalcification showing a triangular shape, it would have been possible to avoid biopsy in benign lesions in 79 patients and only three harmless intraductal lesions would have been overlooked. It is the task of the radiologist to distinguish intraductal calcification from that which is not intraductal.