Abstract P1-10-20: Idiopathic granulomatous mastitis with superimposed tuberculosis mastitis

Abstract Idiopathic granulomatous mastitis (IGM) is a rare condition and exact prevalence is unknown. It may mimic infectious and malignant breast disease and is a diagnosis of exclusion with unknown etiology. Though not life threatening, the pain and disfigurement can be debilitating. In the United States association of IGM with childbearing, lactation, Corynebacterium and Hispanic ethnicity have been reported. Among small retrospective and prospective reviews Hispanic ethnicity accounts for 80-97% of patients. There is no agreed upon treatment and different modalities include a combination of antibiotics, steroids and surgical debridement. We present here a case of a 42-year old woman with a history of pituitary macroadenoma, hyperprolactinemia s/p cabergoline treatment and chronic galactorrhea who presented to breast clinic with chronic breast pain, abscesses and repeated biopsies over 6 years before eventual conformation of IGM diagnosis and TB mastitis. The patient initially presented to an outside hospital with complaints or a right breast abscess that was treated over 2 years with multiple aspirations, I&Ds and oral antibiotics. She had no personal or family history of cancer. Mammogram obtained on presentation to our clinic was BIRADS 2 and multiple biopsies showed chronic and acute inflammation consistent with abscess cavity. The IGM, AFB, fungal and TB testing were all negative and remained negative despite relapsing and remitting symptoms of the right breast. After several months of failed management with antibiotics and aspiration she was started on a prednisone empirically. Multiple biopsies obtained and repeat aspirations remained negative for IGM or infectious etiology. Over 4 months symptoms improved, and steroids were weaned. Symptoms recurred again however after stopping steroids and this time biopsy and culture showed corynebacterium. She was started on doxycyline and kenalog injections into the breast with eventual improvement though not full resolution of her symptoms. Over this entire clinical course lasting 3 years repeat screening mammograms remained normal. She eventually returned with severe bilateral breast pain accompanied by large left breast abscesses. After in office incision and drainage did not provide adequate relief intraoperative drainage of the left breast was planned. A periareolar incision was made and on deeper dissection multiple loculated areas were broken up releasing purulent drainage. The cavity was packed with iodoform gauze. Pathology showed breast tissue with chronic inflammation, granulation tissue and fat necrosis. PAS-F, Gram, and AFB special stains are negative for fungal elements, bacterial organisms, and acid-fast bacilli. The patient slowly improved until 3 months post op when she returns with recurrent left breast symptoms as well as subcutaneous skin nodules on her legs and arms. Pathology at this time was positive for IGM showing granulomatous mastitis and lymphocytic lobulitis. There was some mild improvement with continued kenalog and doxycyline. During a particularly bad recurrent flare a repeat TB quantiferon became positive. Patient was sent to infectious disease to initiate anti-TB treatment and had marked improvement of symptoms. IGM remains poorly understood and though relatively rare can be incapacitating. Some cases, as the one described here, may have superimposed infections exacerbating patient symptoms. Though there has been an association with the Hispanic community there has been little meaningful research investigating etiology or predisposing factors. Understanding these factors may ultimately lead to improved treatments and outcomes. Citation Format: Melissa Rangel, Julie Wecsler, Julia Alexevia. Idiopathic granulomatous mastitis with superimposed tuberculosis mastitis [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2024; 2024 Dec 10-13; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2025;31(12 Suppl):Abstract nr P1-10-20.