Idiopathic Granulomatous Mastitis: A Consensus Report on Treatment and Follow-Up Approaches Based on the Turkish Clinical Classification

Abstract

Objective

The second consensus study on idiopathic granulomatous mastitis (IGM) aimed to establish treatment options based on the clinical classification proposed in the first consensus, standardize criteria for treatment discontinuation, and develop follow-up protocols.

Method

A structured methodology, identical to the first consensus study, was employed. An 11-member working group of breast surgeons experienced in IGM from various clinics across the country was formed. The modified Delphi method was used, with a consensus threshold of 80% agreement.

Results

Three voting rounds were conducted to develop the IGM treatment algorithm. In Round 1, observation was established as the first-line option for Type 1 disease (81%) and pregnancy/lactation cases (85%). Round 2 achieved consensus on systemic steroids (SS) as the first-line treatment for Type 3 cases (84%), combination therapies for resistant cases (82%), and reclassification of recurrent cases to guide treatment planning (94%). In Round 3, consensus was reached on the use of immunosuppressive therapy (IMT) for cases where steroids are contraindicated in Type 3 (81%), the use of IMT for resistant cases (93%), avoiding surgery as the first-line option for Type 1 cases (81%), and requiring complete clinical and radiological response before discontinuing treatment (81%). However, no consensus was reached on the first-line treatment for Type 2 disease.

Conclusion

This consensus study successfully developed a treatment algorithm for IGM, prioritizing observation for Type 1 disease and cases involving pregnancy or lactation, and recommending systemic steroids (SS) and immunosuppressive therapies for Type 3 cases. The findings underscore the critical importance of achieving complete clinical and radiological remission before discontinuing treatment. However, the lack of consensus on the treatment of Type 2 disease highlights the need for further research into this challenging subtype.

Introduction

Idiopathic granulomatous mastitis (IGM) is a benign inflammatory breast disease primarily affecting women of reproductive age. Its etiology remains poorly understood. While rare in Western societies, IGM is more prevalent in Middle Eastern, Mediterranean, Asian, and Hispanic populations, accounting for approximately 0.37–0.59% of all breast clinic referrals in endemic regions [1]. The main challenge with IGM is related to its treatment and management due to the disease’s complex and variable nature.

Various treatment options have been explored, including surgical interventions, steroid therapies, antibiotics, and immunosuppressive agents, with published data on their efficacy and recurrence rates. However, the unclear etiology, low incidence, and variable severity of IGM have resulted in a lack of sufficient prospective randomized studies comparing treatment outcomes. Consequently, no standardized treatment protocol has been universally adopted, and this gap has also been highlighted in recent research [2, 3].

To address these challenges, there has been a critical need for a clinical classification system to standardize effective treatment strategies. Turkey, an endemic region for IGM, has been a leading contributor to the global literature on this condition. The IGM-Turkish Clinical Classification (IGM-TCC) (shown in Fig. 1), introduced in a previous consensus report through collaboration among experienced breast surgeons, radiologists, and pathologists, provides a structured framework for diagnosis and treatment [4].

Fig. 1.

Turkish Clinical Classification for Idiopathic Granulomatous Mastitis (IGM-TCC) [4].

Building on this foundation, the present study aimed to standardize first-line treatment preferences for the clinical subtypes of IGM as defined by the IGM-TCC. By consulting a group of expert breast surgeons, this study seeks to establish evidence-based protocols for treatment discontinuation and follow-up, ultimately improving patient outcomes and consistency in IGM management.

Methodology

Consensus Planning

This study aimed to establish a treatment algorithm for IGM using a structured consensus methodology. Ethics approval was obtained from the Erciyes University Faculty of Medicine Ethics Committee (Ethics No. 2024/220). An 11-member working group, consisting of breast surgeons experienced in IGM from various clinics across the country, was formed. The group conducted a comprehensive literature review and developed an evidence-based study plan addressing key aspects of IGM treatment. The proposed algorithm was designed to be simple, inclusive, prognostic, and practical for use in outpatient settings.

Data Collection and Workshop

A national IGM treatment workshop was held on September 21, 2024, at İzmir City Hospital, with the participation of 62 experts, including breast surgeons, radiologists, and regional surgeons interested in IGM. The workshop facilitated discussions on treatment approaches and enabled participants to share their clinical experiences and insights.

Voting Process

The modified Delphi method was chosen for its ability to systematically synthesize expert opinions through iterative rounds, ensuring robust consensus on complex clinical decisions. The consensus process was conducted using the modified Delphi method over three voting rounds. Digital questionnaires were created using Google Drive forms and distributed to breast surgeons experienced in IGM. The survey was administered to surgeons with at least 10 years of professional experience who manage and treat 20 or more IGM cases annually. Participants were provided with a 10-day response period for each round, with measures implemented to prevent duplicate submissions, ensuring one response per participant.

In the first round, the efficacy of evidence-based treatment options (observation, intralesional steroid, topical steroid, surgical excision, systemic antibiotics, systemic steroids, systemic immunosuppressive therapies, and anti-tuberculosis treatments) was evaluated as first-line therapies for different clinical subtypes of IGM (Type1, Type 2, Type 3, Type 4 resistant, Type 4 recurrent, and pregnancy/lactation cases) (shown in Fig. 2). In the second round, participants were asked to respond with either “agree” or “disagree” on each treatment option (Table 1). Unlike the first round, participants were not required to provide justifications for their responses.

Fig. 2.

IGM Treatment Consensus – results from first round voting (in this round, participants selected multiple options). Consensus was reached only for observation as the first-line treatment for Type 1 disease and patients in pregnancy/lactation. OBS, observation – regular monitoring without active intervention, except for drainage when necessary; ILS, intralesional steroid – steroid injection administered directly into the lesion; TOPS, topical steroid – steroid applied to the skin surface; SURG, surgical excision – surgical removal of the lesion; ABX, systemic antibiotics – antibiotics administered orally or intravenously; SS, systemic steroids – steroids taken orally or intravenously. IMT, immunosuppressive therapy – treatment that suppresses immune system activity (e.g., methotrexate, azathioprine); ATT, anti-tuberculosis therapy – medications specifically targeting tuberculosis infection; COMB, combination therapy – use of multiple treatment modalities together (e.g., SS + SURG/IMT/TOPS/ILS/ABX, IMT + SURG, etc.).

Table 1.

IGM Treatment Consensus – results from second and third round voting

	Round 2, %		Round 3, %		Consensus, yes/no
	agree	disagree	agree	disagree
OBS (±drainage) is the appropriate treatment for Type 2 cases	52	48	55	45	No
ILS is the appropriate treatment for Type 2 cases	66	34	76	24	No
TOPS is the appropriate treatment for Type 2 cases	60	40	71	29	No
SS is the appropriate treatment for Type 2 cases	24	76	46	54	No
ILS is the appropriate treatment for Type 3 cases	37	63			No
SS is the appropriate treatment for Type 3 cases	84	16			Yes
IMT is the appropriate treatment for Type 3 cases	37	63			No
COMB is the appropriate treatment for Type 3 cases	66	34			No
In treating recurrent (Type 4) cases, reclassification based on the IGM-TCC is essential for treatment planning	94	6			Yes
IMT is the appropriate treatment for resistant (Type 4) cases	60	40			No
COMB is the appropriate treatment for resistant (Type 4) cases	82	18			Yes
In Type 3 cases, IMT can be administered if SS are contraindicated			81	19	Yes
In resistant Type 4 cases, IMT is a viable treatment option			93	7	Yes
Surgery plays a role in the treatment of IGM.			74	26	No
In Type 3 and Type 4 cases, SURG can be considered to remove residual disease following systemic therapy			67	33	No
SURG is an option for patients with disease relapse following previous treatment and reclassification as Type 1 or Type 2			45	55	No
SURG should not be considered the first treatment option for Type 1 or Type 2 cases			81	19	Yes
The follow-up interval during treatment should be scheduled every 15 days			23	77	No
The follow-up interval during treatment should be scheduled every month			61	39	No
The follow-up interval during treatment should be scheduled every 1.5–2 months			22	78	No
Physical examination and breast ultrasonography should be performed at each follow-up during treatment			51	49	No
Treatment should only be discontinued upon achieving a CCR, confirmed by both physical examination and radiological assessment			81	19	Yes

Bold text indicates a consensus.

OBS, observation; ILS, intralesional steroid; TOPS, topical steroid; SS, systemic steroid; IMT, immunosuppressive therapy; COMB, combination therapy; IGM-TCC, IGM-Turkish Clinical Classification; SURG, surgical excision; CCR, complete clinical response.

In the third round, participants provided justifications for differing opinions, enabling clarification of the role of surgical treatment, as well as the establishment of treatment termination and follow-up protocols (Table 1). A consensus threshold of 80% agreement was set to establish consensus for each treatment option.

Consensus Development

Based on the voting results, a standardized treatment algorithm was developed. Key agreements were derived from evidence-based principles and voting outcomes. The algorithm outlined treatment options for various IGM subtypes, criteria for treatment discontinuation, and follow-up protocols. Insights from all three voting rounds informed the final recommendations, which aim to streamline and standardize IGM management in clinical practice (Table 2).

Table 2.

Treatment algorithm based on the IGM-TCC

	Initial treatment option	Alternative treatment option1
Pregnancy/lactation	OBS	ILS/TOPS
Type 1 disease	OBS	ILS/TOPS
Type 2 disease	ILS/TOPS2
Type 3 disease	SS	IMT/COMB
Type 4 disease
Resistant	IMT	COMB
Recurrent	According to reclassification
Follow-up	During treatment, follow-up should be scheduled every month
Decision to discontinue treatment	When a CCR is achieved in both physical examinations and radiological assessments

In all types, abscesses should be drained: deep abscesses under ultrasound guidance and superficial abscesses via skin incisions.

OBS, observation – regular monitoring without active intervention, except for drainage when necessary; ILS, intralesional steroid – steroid injection administered directly into the lesion; TOPS, topical steroid – steroid applied to the skin surface; SS, systemic steroids – steroids taken orally or intravenously; IMT, immunosuppressive therapy – treatment that suppresses immune system activity (e.g., methotrexate, azathioprine); COMB, combination therapy – use of multiple treatment modalities together (e.g., SS + SURG/IMT/TOPS/ILS/ABX, IMT + SURG, etc.); CCR, complete clinical response.

Consensus is indicated in bold text.

¹If necessary, this may be considered a subsequent or additional treatment to the initial therapy.

²In our study, the consensus threshold was set at 80%; however, since a high level of agreement was achieved in the 70–80% range, it was recommended as the first-line treatment for Type 2 disease.

Results

First Round (Assessment of Treatment Options)

Out of 50 invited participants, 48 contributed to the first round of voting. Consensus was reached for observation as the first-line treatment for Type 1 disease (81%) and patients in pregnancy/lactation (85%). However, no consensus was achieved for the treatment of Type 2, Type 3, and Type 4 patients. For Type 1 disease, topical steroids were the most preferred treatment following observation (38%) (shown in Fig. 2).

For Type 2 disease, preferences were distributed across observation, intralesional, topical, and systemic steroids, as well as systemic antibiotics, with similar rates (50%, 44%, 42%, 40%, and 38%, respectively). For Type 3 disease, systemic steroids were the most frequently preferred first-line treatment (67%), followed by combination therapies (31%). In Type 4 recurrent cases, systemic steroids were preferred (40%), followed by combination therapies (31%). In Type 4 resistant cases, immunosuppressive therapies (44%) and surgery (38%) were more frequently chosen than other options (shown in Fig. 2).

Second Round (Agreement Refinement)

All 50 invited participants took part in the second round. This round focused on the most selected treatment options for Type 2, Type 3, and Type 4 diseases from the first round. For Type 2 disease, intralesional steroids (66%), observation ± drainage (62%), and topical steroids (60%) were similarly favored as first-line treatments. Systemic steroids were considered unsuitable as a first-line treatment for Type 2 disease by the majority, with only 24% favoring their use. Nevertheless, no consensus was reached for the first-line treatment of Type 2 disease (Table 1).

For Type 3 disease, systemic steroids achieved consensus as the first-line treatment (84%). For Type 4 resistant cases, consensus was reached on combination therapies (82%). Additionally, for recurrent Type 4 cases, consensus was achieved on reclassifying the disease using the IGM-TCC to guide treatment planning (94%) (Table 1).

Third Round (Final Consensus and Refinement of Treatment Guideline)

Of the 50 invited participants, 43 responded in the third round. While intralesional and topical steroids emerged as leading options for Type 2 cases (76% and 71%, respectively), no consensus was reached for the first-line treatment. Consensus was reached on the use of immunosuppressive therapy in cases where systemic steroids were contraindicated for Type 3 (81%), and for resistant Type 4 cases, where immunosuppressive therapies were deemed a viable option (93%) (Table 1).

While formal consensus was not achieved, there was broad acceptance of the role of surgery in IGM management (74%). However, consensus was reached that surgery should not be the first-line treatment for Type 1 and Type 2 disease (81%). Regarding follow-up frequency, no consensus was achieved, though monthly follow-ups were the most accepted approach (61%). Finally, consensus was reached that treatment should only be concluded upon achieving complete clinical response, defined as full physical and radiological recovery (81%) (Table 1).

Discussion

Through this consensus study, we aimed to provide clinicians with a systematic, evidence-based framework to manage idiopathic granulomatous mastitis (IGM), address gaps in treatment standardization, and establish criteria for follow-up protocols and treatment discontinuation. Utilizing a clinical classification system, we stratified IGM into subtypes based on disease severity and developed a selective and targeted treatment algorithm tailored to each subtype.

As a primary recommendation, we advocate for observation and minimal intervention in asymptomatic or mild cases (Type 1 disease), as well as during pregnancy or lactation. This approach minimizes patient burden and avoids unnecessary exposure to medical or surgical treatments, acknowledging the self-limiting nature of IGM in many cases. IGM is a condition in which up to 50% of patients achieve complete remission within 2–24 months without treatment [5]. Studies suggest that milder cases with small lesions (<2 cm) often resolve spontaneously under close observation [6, 7]. Thus, in asymptomatic or mild cases, a cautious watch-and-wait strategy is a reasonable approach after ruling out other potential causes (Table 2).

For cases involving abscess formation, we recommend minimally invasive drainage techniques, such as ultrasound-guided percutaneous drainage, to accelerate recovery while avoiding extensive incisions. In symptomatic and aggressive cases, we prioritize steroid therapy and immunosuppressive agents within a stepwise treatment algorithm. Combination therapies are proposed as options for resistant or recurrent cases [8–14], while curative surgical interventions are reserved for carefully selected patients due to their associated risks and potential complications [9, 10]. This stepwise strategy is intended to balance effective disease control with the benign and frequently self-limiting nature of IGM.

The study highlights consensus on treatment options for Type 1 and Type 3 disease, while the lack of agreement on Type 2 disease underscores the variability in clinical presentations, symptoms, and responses to therapy. Unlike Type 1, which is asymptomatic and often managed with observation, and Type 3, which is severe and typically requires systemic therapy, Type 2 falls into a gray zone, leading to differing opinions. While some authors advocate for steroid use to achieve symptomatic relief, others highlight the potential side effects of steroids and prefer an observation-based approach. This variability underscores the urgent need for prospective studies to refine and optimize treatment recommendations for this subtype. Across all types, achieving full clinical and radiological remission before treatment discontinuation is emphasized to reduce recurrence risks [15, 16].

Although these findings provide a valuable foundation for managing IGM, there are important limitations to consider: presenting limited empirical validation and generalizability, especially for less common IGM subtypes, as the study is based on expert opinion using a consensus-based methodology (the modified Delphi method) rather than robust randomized controlled trials. Additionally, the predominance of Turkey-based experts introduces regional biases, limiting applicability to non-endemic settings. Lack of multicenter clinical evidence, patient-centered outcomes (e.g., quality of life, treatment satisfaction), and prospective validation of the proposed algorithms are further areas to improve. Future studies should include multicenter prospective trials, patient-reported outcomes, and international collaboration to increase the validity, applicability, and generalizability of the proposed management strategies. Integrating such evidence into practice can optimize treatment pathways, reduce care variability, and improve patient outcomes.

Surgical treatment, which was the primary option before 1980, became less common after evidence emerged supporting the efficacy of steroids [17]. Limited resections are associated with high recurrence rates (23–50%) [18, 19], whereas more extensive oncoplastic resections or mastectomies can reduce recurrence rates to 5% [20]. However, these approaches come with higher costs and result in the loss of breastfeeding function. Such aggressive strategies may be excessive for a benign, self-limiting disease and should be reserved for selected cases, ideally in combination with medical therapies. Nonetheless, while formal consensus was not achieved, there was broad acceptance of the role of surgery in IGM management (74%), indicating that surgical intervention remains a consideration in specific clinical scenarios and should not be entirely disregarded in the treatment algorithm.

Lastly, antibiotics play a minimal role in managing IGM as the condition is characterized by the absence of secondary infectious causes. Most patients at tertiary centers receive ineffective antibiotic treatments before referral [1, 11, 21, 22]. This underscores the importance of accurate diagnosis and appropriate treatment. Similarly, since the etiology of IGM is not clearly linked to tuberculosis, anti-tuberculous treatment should only be considered in cases where tuberculosis is confirmed through culture or PCR. In such instances, the condition is classified as secondary granulomatous mastitis rather than idiopathic granulomatous mastitis. Despite variations in the dosage and duration of topical, intralesional, oral steroid, and immunosuppressive treatments reported in the literature [3, 8, 11, 14, 22–32], our standardized treatment approach is outlined in Table 3.

Table 3.

Practical application of treatment modalities in idiopathic granulomatous mastitis

Treatment modalities	Proposed treatment approach
Topical steroid therapy [11, 23]	Prednisolone 0.125% pomade is applied twice daily to the affected breast, with a stretch film for at least 1 h to enhance absorption
	Patients receive initial instructions at the hospital and self-administer treatment at home. The pomade is used on weekdays, with weekend breaks (1-week cycle), and continued until a complete clinical response is achieved
ILS therapy [8, 14, 24–26]	40 mg of methylprednisolone is injected per lesion, with a maximum total dose of 100 mg for multiple lesions. Aspiration is performed if a collection is present
	Injections are given monthly, with a 2-week interval if symptoms worsen. Treatment ranges from 2 to 8 sessions, averaging four
	This protocol can be combined with topical steroids to optimize efficacy
Oral steroid therapy [11, 27–29]	Methylprednisolone (0.5–0.8 mg/kg/day) is given once daily in the morning after meals, with gradual tapering based on clinical and radiological response
	When combined with topical steroids, a lower starting dose (e.g., 0.4 mg/kg/day) may be used while maintaining a gradual tapering approach
	Precaution: restrict salt and sugar intake, monitor for iatrogenic Cushing’s syndrome, and limit treatment to 6 months to minimize complications
MTX therapy [3, 22, 30–32]	Dosing: 5–15 mg/week (PO), increased to 20–25 mg/week if needed, for 6–24 months
	Administration: oral MTX is preferred; switch to SC MTX (12.5–15 mg/week) if intolerable (GI side effects, relapse, or prior failure)
	Supportive therapy: 10 mg/week folic acid; contraception required for women of reproductive age
	Monitoring: CBC and LFTs every 2–4 weeks, with monthly evaluations for efficacy and safety
	Precautions: monitor hepatic, renal, and bone marrow toxicity. Consider azathioprine (AZA) if intolerance or inadequate response occurs

ILS, intralesional/intraparenchymal steroid; MTX, methotrexate; PO, oral; SC, subcutaneous; GI, gastrointestinal; CBC, complete blood count; LFTs, liver function tests; AZA, azathioprine.

Conclusion

This consensus study moves care forward by developing a treatment algorithm based on classification; defining stop rules for treatment; and providing guidance on follow-up. Mild cases are managed by observation or minimal intervention and systemic steroids, immunosuppressive agents, or combination therapies are recommended for more aggressive cases, reserving surgery for a select group of patients. These results form the basis for multicenter trials and international collaborations in the future to calibrate and validate these algorithms. Using patient-reported outcomes in future research will prioritize the needs of patients, increase quality of life, and make the results applicable worldwide.

Statement of Ethics

Ethics approval was obtained from the Erciyes University Faculty of Medicine Ethics Committee (Ethics No. 2024/220). Written informed consent from participants was not required in accordance with local and national guidelines.

Conflict of Interest Statement

The authors have no conflicts of interest to declare.

Funding Sources

This study was not supported by any sponsor or funder.

Author Contributions

Conceptualization and design: Mustafa Emiroğlu, Sadullah Girgin, and Bahadır Güllüoğlu. Data collection: Mustafa Emiroğlu, Nuh Zafer Cantürk, Bahadır Güllüoğlu, Kenan Çetin, Kerim Bora Yılmaz, Mehmet Velidedeoğlu, Sadullah Girgin, Alper Akcan, Özgür Aytaç, Hande Köksal, and Neslihan Cabioğlu. Formal analysis: Mustafa Emiroğlu, Sadullah Girgin, Kenan Çetin, Murat Akın, Mehmet Velidedeoğlu, Kerim Bora Yılmaz, Hande Köksal, and Neslihan Cabioğlu. Methodology and process management: Mustafa Emiroğlu, Kenan Çetin, Kerim Bora Yılmaz, Mehmet Velidedeoğlu, Sadullah Girgin, Alper Akcan, Özgür Aytaç, and Murat Akın. Interpretation of data: Kenan Çetin, Kerim Bora Yılmaz, Mehmet Velidedeoğlu, Sadullah Girgin, Alper Akcan, Özgür Aytaç, Hande Köksal, Neslihan Cabioğlu, and Nuh Zafer Cantürk. Literature review: Kerim Bora Yılmaz, Mehmet Velidedeoğlu, Kenan Çetin, and Neslihan Cabioğlu. Writing – original draft: Kenan Çetin. Writing – review and editing: Kerim Bora Yılmaz, Mehmet Velidedeoğlu, Mustafa Emiroğlu, Kenan Çetin, and Bahadır Güllüoğlu. Supervision: Mustafa Emiroğlu, Kenan Çetin, Kerim Bora Yılmaz, Mehmet Velidedeoğlu, Sadullah Girgin, Murat Akın, Alper Akcan, Özgür Aytaç, Hande Köksal, Neslihan Cabioğlu, Nuh Zafer Cantürk, and Bahadır Güllüoğlu.

Funding Statement

This study was not supported by any sponsor or funder.

Data Availability Statement

All data generated or analyzed during this study are included in this article. Additional inquiries can be directed to the corresponding author.