What are the diagnostic criteria for mastitis (inflammation of the breast tissue)?

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From the Guidelines

Mastitis is diagnosed based on clinical symptoms and physical examination findings, with primary diagnostic criteria including breast pain, redness, swelling, and warmth in the affected area, often accompanied by flu-like symptoms such as fever, chills, malaise, and body aches. The diagnostic criteria for mastitis are primarily clinical, focusing on symptoms such as breast pain, redness, swelling, and warmth, which are often accompanied by systemic symptoms like fever and malaise 1. A thorough breast examination is crucial and may reveal a tender, firm, wedge-shaped area of induration in the affected breast.

Key Diagnostic Considerations

  • Breast pain, redness, swelling, and warmth are key clinical findings.
  • Flu-like symptoms such as fever (typically >38.5°C), chills, malaise, and body aches may accompany these symptoms.
  • A thorough breast examination can reveal a tender, firm, wedge-shaped area of induration.
  • Milk expression might show changes in consistency, with possible purulence or blood.

Laboratory and Imaging Tests

Laboratory tests are not routinely required but can be helpful in certain cases. A complete blood count may show leukocytosis, and milk culture can identify the causative organism (commonly Staphylococcus aureus) in cases of infectious mastitis 1. Ultrasound imaging may be used to differentiate mastitis from breast abscess when there is a palpable mass or when symptoms persist despite appropriate antibiotic therapy. Inflammatory markers like C-reactive protein may be elevated but are nonspecific.

Differential Diagnosis

It's essential to distinguish mastitis from other conditions like breast engorgement, plugged ducts, or inflammatory breast cancer, particularly in non-lactating women or when symptoms persist despite appropriate treatment 1. Early diagnosis and prompt treatment with antibiotics (typically dicloxacillin or cephalexin 500mg four times daily for 10-14 days) along with continued breastfeeding or milk expression are crucial to prevent complications such as breast abscess formation. The most recent and highest quality study 1 supports the importance of clinical diagnosis and prompt antibiotic treatment in managing mastitis effectively.

From the Research

Diagnostic Criteria for Mastitis

The diagnostic criteria for mastitis are based on clinical observations and symptoms. The following are some of the key diagnostic criteria:

  • Fever, malaise, focal breast tenderness, and overlying skin erythema or hyperpigmentation are common symptoms of mastitis 2
  • Clinical diagnosis can be made without the need for laboratory tests or imaging, but milk cultures and ultrasonography may be considered to guide antibiotic therapy and identify abscesses 2
  • Somatic cell count/somatic cell score are common diagnostic tests for the detection of subclinical mastitis 3
  • Culture and polymerase chain reaction can be useful in the diagnosis of an intramammary infection, but have their advantages and disadvantages 3
  • Radiographic imaging features, such as irregular hypoechoic masses, may be suspicious for malignancy, but histopathological findings are necessary for a definitive diagnosis 4

Diagnostic Tests and Procedures

The following diagnostic tests and procedures may be used to diagnose mastitis:

  • Clinical examination and medical history 2
  • Milk cultures and ultrasonography 2
  • Somatic cell count/somatic cell score 3
  • Culture and polymerase chain reaction 3
  • Radiographic imaging, such as ultrasound 4
  • Histopathological analysis, such as core-cut biopsy 5

Special Considerations

The following special considerations should be taken into account when diagnosing mastitis:

  • Idiopathic granulomatous mastitis (IGM) may require a combination of clinical, imaging, and histopathological findings for diagnosis 5
  • IGM may be treated with anti-inflammatory therapy, such as colchicine, vitamin E, and local compresses 5
  • Patients with mastitis should be evaluated for underlying systemic diseases, such as lupus or other autoimmune disorders 4

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Mastitis: Rapid Evidence Review.

American family physician, 2024

Research

Methods for Diagnosing Mastitis.

The Veterinary clinics of North America. Food animal practice, 2018

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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