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

Objective. - Collagenous spherulosis of the breast is an uncommon localized pattern of basement membrane material deposition that may be mistaken for atypical proliferations or carcinoma. This report describes 9 cases in which the predominant or exclusive appearance of the spherules was basophilic instead of eosinophilic. Design. - The files of all cases of collagenous spherulosis diagnosed at the Armed Forces Institute of Pathology were reviewed to ascertain the frequency of diagnosis. Results. - Spherulosis with a predominantly basophilic pattern had a histochemical and immunohistochemical profile similar to collagenous spherulosis and was associated with more collagenous-appearing forms in 7 of 9 cases. Review 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 of spherulosis. They are underrecognized by pathologists and maybe mistaken for atypia or malignancy.