Clinical practice guidelines for diagnosis and treatment of patients with non-puerperal mastitis: Chinese Society of Breast Surgery (CSBrS) practice guideline 2021



## Level of evidence and recommendation strength
Level of evidence standard [bib_ref] Clinical practice guidelines for sentinel lymph node biopsy in patients with early-stage..., Ye [/bib_ref] Recommendation strength standard [bib_ref] Clinical practice guidelines for sentinel lymph node biopsy in patients with early-stage..., Ye [/bib_ref] Recommendation strength review committee A total of 79 members of the voting committee of this guideline, including 66 breast surgeons (83.5%), four oncologists (5.1%), four radiologists (5.1%), two pathologist (2.5%), one radiation therapist (1.3%), and two epidemiologists (2.5%).

## Target audience
Chinese breast disease specialists.

## Recommendations
Recommendation 1: Diagnosis. Core needle biopsy [bib_ref] Diagnostic accuracy of large-core needle biopsy for nonpalpable breast disease: a meta-analysis, Verkooijen [/bib_ref] [bib_ref] Diagnostic agreement in the evaluation of image-guided breast core needle biopsies: results..., Collins [/bib_ref] I A

# Method

## Level of evidence

## 1.2.2
Vacuum-assisted breast biopsy [bib_ref] Interdisciplinary consensus recommendations for the use of vacuum-assisted breast biopsy under sonographic..., Hahn [/bib_ref] II B * On microscopic examination of hematoxylin and eosin-stained sections, periductal mastitis is characterized by greatly dilated ducts filled with pink material, abundant fatty acid crystals, and infiltration of lymphocytes, plasma cells, and neutrophils around the dilated ducts. Granulomatous lobular mastitis manifests as multifocal non-caseating granulomas centered on lobular units of the breast and composed mainly of epithelioid cells, Langhans giant cells, neutrophils, and lymphocytes. They vary in size and may be accompanied by microabscesses. [bib_ref] Management of breast abscesses in nonlactating women, Rizzo [/bib_ref] I A 3.1.2 Needle aspiration with ultrasound guidance may be considered for unilocular abscesses (<3 cm) [bib_ref] Ultrasound guided needle aspiration versus surgical drainage in the management of breast..., Chandika [/bib_ref] [bib_ref] Comparison of incision and drainage against needle aspiration for the treatment of..., Naeem [/bib_ref] II A 3.2 Sinus and fistula 3.2.1 Fistulectomy [bib_ref] Recurrent periductal mastitis: surgical treatment, Taffurelli [/bib_ref] III B

# Discussion
The causes of NPM are unclear and there is a lack of evidence-based data on diagnosis and treatment. In this guideline, the recommendations for means of diagnosing NPM and obtaining biopsies, pathological classification, and drug and surgical treatment are based on a combination of findings of retrospective studies and the panel members' experience in diagnosis and treatment.
Comprehensive assessment of patients with NPM should include identifying clinical manifestations, performing auxiliary investigations, and determining the histopathology. To make this diagnosis, breast tuberculosis and specific granulomatous lesions must be excluded. The panel recommends breast ultrasound as the optimal imaging modality for patients with suspected NPM; this can be used to evaluate the lesion's characteristics and the number and extent of any abscesses. [bib_ref] Idiopathic granulomatous mastitis: a 10-year study from a multicentre clinical database, Co [/bib_ref] There is limited evidence for the value of mammography in diagnosing NPM. Breast magnetic resonance imaging has greater specificity. Diffusion-weighted imaging may assist in differentiating between PDM and GLM [bib_ref] Diffusionweighted imaging in relation to morphology on dynamic contrast enhancement MRI: the..., Zhang [/bib_ref] ; however, because there is little evidence for this, the panel does not recommend magnetic resonance imaging as a routine imaging modality.
The clinical manifestations of PDM and GLM are similar; however, the treatment and prognosis differ. The panel recommends that NPM be diagnosed by pathological examination of a specimen and considers that core needle biopsy is the optimal means of obtaining the required tissue. In patients undergoing incision and drainage, a specimen can also be taken from the wall of the abscess cavity. Because fine-needle aspiration yields such a small amount of tissue, the panel does not recommend it as a routine means for pathological examination in patients with NPM.
The role of corticosteroids in the treatment of GLM has recently attracted increasing attention. Retrospective studies have shown that oral steroid treatment is effective in 72% to 86% of cases, the ipsilateral recurrence rate being 4% and the contralateral recurrence rate 0.97%. [bib_ref] Granulomatous mastitis: presentations, diagnosis, treatment and outcome in 206 patients from the..., Aghajanzadeh [/bib_ref] [bib_ref] Factors related to recurrence of idiopathic granulomatous mastitis: what do we learn..., Uysal [/bib_ref] A meta-analysis has shown similar rates of recurrence of GLM after medical versus surgical treatment. [bib_ref] Comparison of conservative versus surgical treatment protocols in treating idiopathic granulomatous mastitis:..., Zhou [/bib_ref] However, medical treatment is less traumatic; the panel therefore considers that oral steroid therapy can be given priority to GLM patients. Surgical treatment enables accurate pathological diagnosis and removal of affected tissue. Studies have shown that surgery is effective in 79% to 91.7% of cases, the recurrence rate being 1% to 50%. [bib_ref] Idiopathic granulomatous mastitis: in search of a therapeutic paradigm, Wilson [/bib_ref] [bib_ref] Experience of treatment of patients with granulomatous lobular mastitis, Hur [/bib_ref] Surgical complications include delayed incision healing, poor cosmetic outcomes, breast fistula formation, nipple retraction, skin flap necrosis, hematoma, persistent infection, and pain. The panel has made no recommendations regarding immunosuppressive treatment because of the lack of high-level evidence for this treatment modality.
Patients with pathologically confirmed PDM and sinus formation may have non-tuberculous mycobacterial infection. In such cases, 9 to 12 months of antimycobacterial treatment is reportedly effective. [bib_ref] Antimycobacteria drugs therapy for periductal mastitis with fistula (in Chinese), Yu [/bib_ref] In view of the lack of definitive evidence concerning the causes of PDM, the panel recommends collecting specimens for microscopic examination and bacterial culture from patients with suspected NPM. If possible, DNA sequencing should be used to identify pathogenic bacteria. The panel believes that, in patients with PDM, surgical treatment in general, and the specific procedure in particular, should be selected on the basis of the clinical stage of the disease and type of patient. Appropriate timing of surgery is important. The decision to perform a mastectomy should be made with care.
Drainage is the mainstay of treatment when breast abscess formation. Pus can be drained by ultrasound-guided puncture or an incision into the abscess. In the absence of high-level evidence, the panel considers that <3 cm unilocular abscesses should be drained by ultrasoundguided aspiration, whereas consideration should be given to surgical incision and drainage as first-line therapy for larger (clinically >3 cm), multiloculated, or longstanding abscesses.
Appendix: Pathological features of periductal mastitis and granulomatous lobular mastitis Periductal mastitis, http:// links.lww.com/CM9/A563.

## Conflicts of interest
The expert committee for these guidelines declares no conflicts of interest. These guidelines are intended to serve as a reference for breast disease specialists in clinical practice. They are not to be used as a basis for medical evaluation, nor to play an arbitrating role in the handling of any medical disputes. Additionally, these guidelines are not intended as a reference for patients or non-breast specialists. The Chinese Society of Breast Surgery assumes no responsibility for consequences arising from the inappropriate application of these guidelines and reserves the right to interpret and revise them as necessary.