The nature of breast dense core granules: uranaffin reactivity.

In this study breast tissue that contained ultrastructural dense core granules has been examined from 24 patients. The possible neuroendocrine characteristics of the granules were studied using the uranaffin reaction and an ultrastructural argyrophil stain. The tissue included 15 breast carcinomas and nine benign samples. Two types of breast dense core granules can be distinguished on the basis of intracellular distribution patterns and histochemical reactivity. Type I dense core granules are the most common and they were found subluminally distributed in non-pathological tissues and benign lesions as well as carcinomas. They were uranaffin-negative and are unlikely to be of endocrine nature. Type II dense core granules were found only in four carcinomas, where they occurred abundantly throughout the cytoplasm. These granules were uranaffin-positive and argyrophilic and thus exhibited characteristics consistent with neuroendocrine structure.