A very rare case of eosinophilic mastitis

Abstract Introduction Eosinophilic mastitis caused by eosinophil infiltration of the mammary gland is very rare. To date, no report has been published on treating patients with this disorder using anti-allergic drugs. Steroids are commonly used in these cases, but have greater burden. Presentation of case A 33-year-old woman presented to the author’s clinic with a tumor and pain in the upper inner quadrant of the left breast. She underwent core needle biopsy (CNB) and was diagnosed with eosinophilic mastitis based on histopathological analysis. The serum eosinophil count at the time of biopsy increased to 1560/μL. She was administered 100 mg of suplatast tosilate (brand name: IPD capsule 100), an anti-allergic drug, 3 times daily after each meal. Thereafter, the patient’s symptoms improved and her serum eosinophil count returned to normal after 4 months. To date, the patient has been recurrence-free for 3 years since the first presentation. Discussion Organ damage induced by eosinophil infiltration was limited to the mammary gland and improved with anti-allergic drug administration. Conclusion This report presents the successful treatment of an isolated case of eosinophilic mastitis solely using anti-allergic drugs.