Collagenous spherulosis, also mucinous spherulosis and simply spherulosis, is a benign finding in breast pathology. It is almost always an incidental finding, though it is occasionally associated with calcifications, which may lead to a biopsy.
It is important to correctly identify, as it can be confused with atypical ductal hyperplasia, cribriform ductal carcinoma in situ (DCIS), and adenoid cystic carcinoma.
Collagenous spherulosis is characterized by a tubular/cribriform architecture with intratubular eosinophilic material that classically is arranged like the spokes of a wheel ("radial spikes"). There is usually no mitotic activity, and two cells populations (epithelial & myoepithelial) are present, like in benign breast glands.
The lesions are typically small (less than 50 spherules per lesion, less than 100 micrometers in size) and may be multifocal.