Spherulosis of the breast - A spectrum of mucinous and collagenous lesions

Objective.-Collagenous spherulosis of the breast is an uncommon localized p attern of basement membrane material deposition that may be mistaken for at ypical proliferations or carcinoma. This report describes 9 cases in which the predominant or exclusive appearance of the spherules was basophilic ins tead of eosinophilic. Design.-The files of all cases of collagenous spherulosis diagnosed at the Armed Forces Institute of pathology were reviewed to ascertain the frequenc y of diagnosis. Results.-Spherulosis with a predominantly basophilic pattern had a histoche mical and immunohistochemical profile similar to collagenous spherulosis an d was associated with more collagenous-appearing forms in 7 of 9 cases. Rev iew of 81 cases showed that collagenous spherulosis was correctly diagnosed in 15% of referrals and was mistaken for intraductal or invasive carcinoma in 11% of cases. Conclusions.-Mucinous and collagenous patterns appear to be related forms o f spherulosis. They are underrecognized by pathologists and maybe mistaken for atypia or malignancy.