(13.16) A Case of Idiopathic Granulomatous Mastitis in Hyperprolactinemia

Idiopathic granulomatous mastitis (IGM) is an inflammatory breast disorder characterized by a painful breast mass that mimics other conditions including malignancy or abscess. IGM has infectious, autoimmune, and hormonal etiologies, including pregnancy, lactation, and hyperprolactinemia. We present a case of IGM in a patient with recurrent hyperprolactinemia after failed trial of cabergoline discontinuation.


Case(s) Description :

A 32-year-old nulliparous female with history of hyperprolactinemia presented with recurrent mastitis after stopping cabergoline. She was diagnosed with hyperprolactinemia at 20 years old during workup for oligomenorrhea and galactorrhea. She reported diagnosis of pituitary microadenoma, however prior records were not available and repeat brain MRI at 30 years old showed only a 5 mm pituitary cyst. She was treated with cabergoline, and prolactin (PRL) decreased from 100 ng/mL to normal (2.8-29.2 ng/mL) in 4 months. Cabergoline was weaned to 0.25 mg twice weekly before discontinuation after 2 years of therapy with persistent PRL suppression.

The patient developed bilateral breast masses within a month of stopping cabergoline. Mammogram and breast ultrasound showed bilateral dilated ducts with fat and debris concerning for infection, and she was treated with antibiotics. Repeat PRL 3 months after stopping cabergoline rose from 14.3 ng/mL to 76 ng/mL. Cabergoline was resumed and PRL normalized in 5 months. She had initial resolution of breast symptoms, however developed recurrent right breast abscesses requiring antibiotics (penicillin, clindamycin, doxycycline, ciprofloxacin) and incision and drainage. Alternative diagnoses such as malignancy and IGM in the setting of PRL excess were considered. Core biopsy was performed and showed lymphohystiocytic infiltrate with suggestion of a non-necrotizing granuloma consistent with IGM. She was treated with prednisone and her right breast mass decreased in size. She has had no disease recurrence in 6 months although steroids were only recently discontinued. The plan is for serial imaging to ensure disease resolution while continuing cabergoline for hyperprolactinemia.


Discussion :

The etiology for IGM in the setting of hyperprolactinemia is unclear but likely has to do with PRL’s role in normal breast tissue development and lactation. It is important for clinicians to recognize this association as PRL suppression may improve IGM treatment response and reduce recurrence in these cases. Our patient developed breast symptoms within a month of stopping cabergoline with recurrent hyperprolactinemia confirmed shortly after. She has had a positive response to prednisone and cabergoline, but long-term response is to be determined.