Red flags for the differential diagnosis of granulomatous mastitis: a case report

BACKGROUND: Granulomatous mastitis (GM) is a rare benign chronic inflammatory breast disease. GM presents as a heterogeneous illness with variable clinical presentations, and its diagnosis is usually made by exclusion. There are no guidelines for the treatment of GM. This manuscript describes the management of a patient with GM, initially unsuccessfully treated outside our clinic under a diagnosis of mastitis. The patient’s history, physical examination, and needle biopsy flagged the patient’s findings as nonmalignant; however, imaging studies indicated a tumor. Differential diagnosis became a critical element of her care. This case report represents a valuable resource to foster more assertive clinical practice in managing patients with GM. The case coordination and its course were led by a team from an outreach clinic that provides health care services to underserved communities in the state of Michigan. CASE PRESENTATION: A 41-year-old G1P1 Hispanic female immigrant from Central America presented with a rare breast disease, granulomatous mastitis. A similar presentation occurred 5 years before pregnancy when she had an episode of pain and swelling in the left breast, which resolved spontaneously. She sought our services after being diagnosed with mastitis that was unsuccessfully treated. Physical examination revealed a nodular mass in the outer quadrants of the left breast without regional lymphadenopathy. Needle biopsy showed fibrohistiocytic and florid inflammatory reactions, with no evidence of invasive carcinoma. However, this result was inconsistent with the degree of abnormality revealed by the mammogram (BI-RADS grade 5), ultrasound, and physical examination. Full incisional biopsy revealed cystic neutrophilic GM. The surgical procedure, antibiotics, and corticosteroids resulted in a successful combination to secure the stable control of the symptoms and progression of this rare benign breast disease to date. CONCLUSIONS: This patient’s case highlights the importance of integrated communication among front-line primary care and other health care professionals to reduce the risk of invasive procedures and avoid institutional costs. GM is a rare disease. We raised the manifold red flags in which the multiple professional chains recruited to care for this patient were concerning for advanced breast cancer. The lack of experience and evidence-based medicine contributed to the contradictory interpretation of the findings on GM's diagnosis.