Objective: To describe the radiological and clinical features of adult non-puerperal mastitis and to determine the most accurate method of preventing unnecessary surgical procedures.
Methods: Clinical and imaging findings were retrospectively reviewed in 51 females with non-puerperal mastitis, which was confirmed by biopsy/surgical pathology. All 51 patients had pre-operative MRI; 45 patients also had sonograms and 25 also had mammograms, pre-operatively.
Results: Of the 51 cases with non-puerperal mastitis, 94.1% (48/51) were confirmed as having acute or chronic inflammation, and the other 3 had plasma cell mastitis; areola papillaris inflammation was found in 39.2% (20/51) of the cases. Overall, 6 of the 25 cases that were examined with mammography and 2 of the 45 cases that were examined with sonography appeared normal, but all 51 lesions were positively identified on MRI. Asymmetrical density (12/25) on mammograms and solitary or separated/contiguous, clustered, hypoechoic mass-like lesions (31/45) on ultrasound were the most common signs of non-puerperal mastitis. On enhanced MRI, 90.2% (46/51) of patients showed non-mass-like enhanced lesions. Multiple regional enhancements in the pattern of distribution (32/46) and separated or contiguous, clustered, rim-like enhancements in the pattern of internal enhancement (29/46) were the most common manifestations in non-mass-like enhanced lesions. Of the 51 patients, mastitis Type 1 and Type 2 in the time-signal intensity curve were detected in 47.1% and 51.0% of the patients, respectively. The breast imaging reporting and data system categories with the highest number of patients were Category 0 (9/25) on mammography, Category 4a on sonography (18/45) and Category 4a on MRI (29/51).
Conclusion: The findings from mammography and ultrasound are non-specific; therefore, using MR can be helpful in the diagnosis, especially in the presence of non-mass-like enhancements that are multiple, regional, separated, or contiguous, clustered and rim-like.
Advances in knowledge: Mastitis is often neglected because of the lack of typical clinical signs and symptoms. This study has assessed and described the clinical features and imaging findings of adult non-puerperal mastitis on mammograms, sonograms and MRI and found that MRI is more specific in the diagnosis of disease.