OBJECTIVETo investigate the morphological features, immunohistochemical phenotype, diagnosis and differential diagnosis of collagenous spherulosis of the breast.

METHODSClinicopathologic observation, immunohistochemistry using EnVision method and histochemical staining were applied in 33 cases of collagenous spherulosis of the breast.

RESULTSCollagenous spherulosis of the breast was a benign lesion, consisting of proliferative myoepithelial and ductal epithelial cells. These cells were arranged in a cribriform pattern with esinophilic, round, oval or star-shaped fibrillary spherules in the lumen.SMA, calponin and p63 by immunohistochemistry identified the proliferative myoepithelium, while E-cadherin identified the proliferative ductal epithelial cells. The esinophilic spherules were stained with collagen type IV, AB-PAS and reticulin. Collagenous spherulosis was often found in sclerosing adenosis.

CONCLUSIONSCollagenous spherulosis of the breast is often associated with other diseases. It has special morphological presentation and is easily confused with malignant tumors such as adenoid cystic carcinoma or cribriform carcinoma in situ, and needs to be differentiated from these disease entities.