Collagenous spherulosis: an ultrastructural study

Ultrastructural findings are described in two cases of collagenous spherulosis associated with intraductal hyperplasia and sclerosing adenosis. The spherules showed a variable composition of basement membrane, banded collagen, and mineral deposition. Some spherules were connected to the periacinal stroma by a thin pedicle. The authors propose that spherules represent a peculiar form of stromal invagination that could be seen in a variety of breast lesions, rather than a form of intraductal hyperplasia.