Clinical score separates idiopathic granulomatous mastitis from breast cancer mimics

A retrospective study has developed a quantitative clinical score designed to help distinguish idiopathic granulomatous mastitis, or IGM, from other conditions that can look similar on breast examination and medical imaging. The system combines information about symptom onset, clinical features and radiographic findings, producing a continuous score from 1 to 50. In the study population, a score of at least 24.5 classified IGM with 93% sensitivity and 95% specificity, according to the researchers’ analysis.

IGM is a benign inflammatory condition of the breast, but it can resemble both ordinary mastitis and breast cancer, including inflammatory breast cancer. The research team adapted the Komen Inflammatory Breast Cancer scoring system to address this diagnostic overlap. They reviewed the electronic medical records of patients whose biopsies confirmed IGM between 2014 and 2025, then compared their scores with those assigned to four groups: IGM, inflammatory breast cancer, lactational or non-lactational mastitis, and locally advanced breast cancer. Because the study was retrospective and based on records from a single institution, the results describe performance under the available clinical data rather than proving that the tool will work equally well in every hospital or patient population.

The 148 patients with biopsy-proven IGM had a mean age of 37.2 years. The group was predominantly Hispanic, representing 56.8% of participants, while Asian patients accounted for 26.7%. Certain symptoms and signs were common: all patients had pain or a painful breast mass, 94.6% had erythema, 87.8% had phlegmon, and 77.7% had a fistula or draining wound. Imaging also revealed recognizable patterns. A breast mass with an associated collection appeared in 84.6% of cases, and 38.9% had multiple masses or collections. These findings supplied the clinical and radiologic information used to construct the continuous scoring scale.

Patients with IGM received a mean score of 35.5, compared with 14.4 for inflammatory breast cancer, 18.0 for mastitis and 15.2 for locally advanced breast cancer. Statistical comparisons found significant differences between the IGM group and each of the other groups, with p-values of 0.05 or lower. The researchers used Youden’s index to identify 24.5 as the optimal threshold for predicting IGM, yielding the reported 93% sensitivity and 95% specificity. The study therefore supports the score as an objective aid for evaluating patients whose breast inflammation may be confused with malignancy, although additional prospective research would be needed to establish its usefulness across broader populations and independent clinical settings.

Subject of Research: Development and retrospective evaluation of a clinical scoring system for idiopathic granulomatous mastitis

Article Title: A breast clinical scoring system to identify women with Idiopathic granulomatous Mastitis

Article References: Mehra, S., Hong, J., Yeh, C., Su, J., Stone, K., Wapnir, I., & Tsai, J. (2026). A breast clinical scoring system to identify women with Idiopathic granulomatous Mastitis. Breast Cancer Research and Treatment, 220(1), Article 11. https://doi.org/10.1007/s10549-026-08102-4

Image Credits: AI Generated

DOI: 10.1007/s10549-026-08102-4

Keywords: idiopathic granulomatous mastitis, breast inflammation, clinical scoring, diagnostic accuracy, inflammatory breast cancer, breast imaging, retrospective study, mastitis, breast, clinical, scoring, system