Risk factors for idiopathic granulomatous mastitis: scoping review

Idiopathic granulomatous mastitis (IGM) is a rare, benign, inflammatory breast condition. The diagnostic challenge can cause delays in diagnosis and treatment. The quality of evidence for the diagnosis and management of IGM is low. A scoping review of existing literature was conducted to determine risk factors for IGM, with the aim of informing clinical suspicion, earlier diagnosis, and treatment of this condition.

A scoping review of the MEDLINE, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) databases (2003-2023) was performed following PRISMA-ScR guidance. Data on demographics, reproductive history, hormonal factors, body mass index (BMI), and smoking were extracted and subjectively compared to appropriate published population demographics of the relevant risk factors.

In all, 230 studies involving 13 062 patients were included. Most common countries of publication origin were Turkey (86 papers; 5233 patients), the USA (30 studies; 764 patients), and China (23 papers; 3990 patients), with three papers (25 patients) from the UK. Most common ethnicities reported were Hispanic (36%), Turkish (20%), White (9%), and Middle Eastern (8%). The mean age (34.7 years) was consistent across the literature, except for UK publications (mean age 50 years). High rates of history of pregnancy (> 90%) were reported, except for UK papers (68%); 64-85% of patients had a history of lactation; and the prevalence of hyperprolactinaemia (reported in 18% of papers) was 5% (versus 0.4% in the general population). BMI appears to match age and country-equivalent BMIs, with no association with diabetes. Smoking association is inconclusive.

Risk factors for IGM appear centred on reproductive, hormonal, ethnicity, and possibly geographical factors, although the data are limited by inconsistent reporting, small study sizes, and retrospective study designs.