Dermal calcifications in fixed orientation: the tattoo sign.

Calcifications located in the dermis of the breast may appear indistinguishable from intramammary calcifications. The authors present a sign, called the tattoo sign, that can help radiologists identify dermal calcifications. When mammograms are compared, calcifications that maintain a fixed relationship to each other suggest a dermal location. This can be verified with standard techniques. Understanding the tattoo sign may help prevent unnecessary needle localization and biopsy procedures.