Breast Abscess

Etiology

Lactational breast abscesses develop as a progression of infectious mastitis. Although breast skin, tissue, and milk were previously considered sterile, each harbors a diverse microbiome whose clinical significance is still being investigated.[4] Tissue trauma, including nipple or skin damage and mechanical trauma associated with breastfeeding, combined with inflammation and disruption of the breast microbiome, or “mammary dysbiosis,” can contribute to breast infection and subsequent abscess formation.[5] Risk factors associated with progression from lactational mastitis to breast abscess include more than 42 days postpartum, symptom onset lasting longer than 2 days, milk or pus cultures positive for methicillin-resistant Staphylococcus aureus (MRSA), a history of massage performed by nonprofessionals, lesions involving the nipple-areolar complex, and, paradoxically, a temperature below 38.5 °C, which may indicate delayed presentation.[6]

Nonlactational breast abscesses can develop secondary to ductal abnormalities and predisposing factors, eg, diabetes or smoking. Nipple piercing is associated with subareolar breast abscess formation. Smoking also demonstrates a strong association with recurrent breast abscesses.[7][3]

Microbiology

Bacterial species isolated from lactational breast abscesses are most often skin-colonizing flora, including Staphylococcus aureus (and other Staphylococcus species, including S epidermidis, S lugdunensis, and S hominis) and Streptococcus species, including S mitis, S salivarius, S pyogenes, and S agalactiae.[5] MRSA is becoming increasingly common.[8] Staphylococcus and Streptococcus species are also commonly found in healthy breast microbiomes. In the setting of an abscess, an overgrowth or imbalance is implicated. 

Staphylococcus aureus is also the most commonly implicated pathogen for nonlactational breast abscess. Other common pathogens in nonlactational breast abscesses include Streptococcus species, anaerobic bacteria, and mixed flora.[ABS. Pesce et al. Abscess/Infections/Periareolar Mastitis. 2021][7][8] Recurrent abscesses show higher rates of mixed bacterial and anaerobic infections compared to primary abscesses.[3]

In one retrospective cohort study conducted in Ireland, gram-positive bacteria were identified in 71% of lactational breast abscesses, MRSA in 11.8%, and anaerobes in 17.7%. For nonlactational breast abscesses, gram-positive bacteria were identified in 58.2% of cases, MRSA in 7.7%, anaerobes in 25.3%, gram-negative bacteria in 7.7%, and Candida in 1.1%.[9] 

Epidemiology

Breast abscesses occur most frequently among premenopausal females aged 18 to 50 years.[1] However, neonates, adolescents, and males can also develop breast abscesses.[10][11][12]

Lactational Breast Abscess

Lactational mastitis affects an estimated 1% to 24% of lactating people.[1] Among individuals with lactational mastitis, approximately 3% to 11% may progress to breast abscess formation.[5] The estimated overall global incidence of breast abscess among lactating individuals ranges from 0.1% to 3%.[13] Most lactational breast abscesses develop between 3 and 8 weeks postpartum.[14]

Reported risk factors for breast abscess include primiparity, maternal age older than 30 years, gestation exceeding 41 weeks, breastfeeding difficulties, nipple trauma, and employment outside the home.[14][15] High-quality studies examining risk factors for lactational mastitis remain limited, with even fewer studies specifically addressing breast abscess risk factors. Because lactational breast abscesses most commonly represent progression from mastitis, the two conditions may share several risk factors. A systematic review identified nipple damage or nipple pain as the factor most consistently associated with lactational mastitis.[16] Additional risk factors for lactational mastitis include nipple cream use, nipple shield use, wearing a tight bra, a history of lactational mastitis, breastfeeding difficulties, hyperlactation, and breast pump use.[16][17] Studies assessing age, education, income, occupation, and access to private care have produced mixed results.[16]

A retrospective cohort study of childbirth-associated breast infections, including mastitis, abscess, and nipple infection, evaluated cases in the United States over 10 years. Most breast abscesses occurred among individuals aged 22 to 30 years (50.4%), followed by those aged 31 years and older (24.8%), 18 to 21 years (18.7%), and 12 to 17 years (6.1%).[18] Within this study, Black women had a disproportionate share of admissions for breast abscess compared with mastitis, accounting for 60.0% versus 37.9%, respectively. Among white women, the corresponding proportions were 33.9% versus 65.1%.[18] Breast abscess incidence decreased as income quartile increased. Among patients presenting with breast abscess, 51.1% had Medicaid insurance and 40.0% had private insurance.[18]

A retrospective study from China comparing single lactational breast abscesses with multiple abscesses (defined as 2 or more) identified several factors associated with multiple abscesses. These factors included mastitis occurring before 6 weeks postpartum, separation from the infant, nonexclusive breastfeeding, an inverted nipple, nipple pain during breastfeeding, breast massage performed by nonmedical staff, and fever, redness, and swelling of the breast skin.[19]

Nonlactational Breast Abscess

A study evaluating risk factors for breast abscess, with 93% of cases classified as nonlactational, reported a mean patient age of 38 years. Univariate analysis identified smoking as a significant risk factor, with an odds ratio of 8.0, along with diabetes mellitus with an odds ratio of 5.7, nipple piercing with an odds ratio of 10.2, and obesity with an odds ratio of 3.6.[7] Multivariate analysis demonstrated that smoking remained a significant risk factor, with an odds ratio of 6.15, while nipple piercing remained significantly associated with subareolar breast abscess, with an odds ratio of 20.26. Nonlactational breast abscesses have a higher recurrence rate than lactational abscesses, with reported rates of 53% to 57%.[3][7][3] Increasing age, smoking, and surgical treatment have been associated with recurrence.[7]

In a study of 89 patients diagnosed with a primary breast abscess requiring surgical intervention, 14% of cases were lactational, and 86% were nonlactational. Compared with the general population, patients with primary breast abscesses included a disproportionately high percentage of African American individuals (64% vs. 12%), individuals with obesity defined by a body mass index greater than 30 (43% vs. 22%), and tobacco smokers (45% vs. 23%).[3]

Risk factors may vary according to geographic region. A small study of nonlactational breast abscesses in India found that most cases occurred among females aged 31 to 50 years. Associated risk factors included tobacco consumption, which demonstrated the strongest association, along with diabetes mellitus, tuberculosis, and HIV.[European Journal of Cardiovascular Medicine. Breast Abscess in Non-lactating Women- a Clinical Study in a Tertiary Care Centre. 2025]

Pathophysiology

Breast anatomy provides an essential foundation for understanding the pathophysiology of breast abscesses. The breast consists of glandular tissue, fibrous connective tissue, and adipose tissue, supported by an extensive network of blood vessels, lymphatic vessels, and nerves. The glandular system contains 15 to 20 lobes arranged in a radial, spoke-like pattern extending from the nipple. Each lobe contains 20 to 40 lobules. The terminal duct lobular unit, composed of lobules and their associated ducts, is the functional unit responsible for milk production. Within the terminal duct lobular unit, small milk-producing sacs called alveoli or acini contain cuboidal epithelial cells that produce milk proteins and lipids. The lobes produce milk, while the ducts transport milk. Each lobe drains into a lactiferous duct that widens to form lactiferous sinuses that converge at the nipple (see Images. Breast Sagittal View and Terminal Duct Lobular Unit). During lactation, the lactiferous sinuses function as milk reservoirs.[20] The mammary gland remains dynamic and hormonally responsive throughout life, undergoing changes associated with puberty, the menstrual cycle, pregnancy, breastfeeding, cessation of breastfeeding, menopause, and aging.[21]

Contrary to earlier beliefs, available evidence does not establish milk stasis as the root cause of breast abscess formation. Excessive expression of the lactating breast in an effort to completely “empty” milk can promote overproduction and ultimately worsen breast inflammation, as supply-and-demand dynamics regulate milk production. Although nipple trauma commonly accompanies lactational mastitis, available data remain confounded, and evidence indicates that breast infection does not result solely from retrograde bacterial infection.[5][22]

Breast inflammation encompasses a spectrum of disorders that can progress through several stages. Ductal lumen narrowing, often referred to colloquially as “plugging,” represents an early step in the pathogenesis. Rather than a single duct becoming physically “plugged” with milk, ductal narrowing reflects focal induration and congestion of breast tissue. Edema and hyperemia associated with hyperlactation and mammary dysbiosis can contribute to this process. Ductal narrowing can progress to inflammatory mastitis, which produces erythema, edema, and pain in a segmental distribution involving the ducts, alveoli, and surrounding connective tissue. Inflammatory mastitis can subsequently progress to bacterial mastitis, during which bacterial infection promotes neutrophil recruitment and local tissue injury. Ductal narrowing and inflammatory mastitis can also produce a phlegmon, representing a fluid collection that deep massage may exacerbate.[5][23] An abscess develops when a fluid collection associated with bacterial mastitis or a phlegmon becomes infected. Breast abscesses generally present as well-defined, palpable collections of infected fluid or pus and may become encapsulated by fibrin.[5][23]

Alterations in the breast microbiome may also contribute to the pathogenesis of breast abscesses. During healthy lactation, numerous bacterial species can inhabit the mammary gland ecosystem. The breast microbiome reflects interactions between maternal skin flora and infant oral flora and can also be influenced by factors, eg, mode of delivery (cesarean versus vaginal). Mammary dysbiosis, characterized by an imbalance in the breast microbiome, together with local inflammation, can promote progression from mastitis to abscess formation.[24]

Nonlactating breasts also contain a microbiome, although this state has received less extensive research. The pathogenesis of nonlactational breast abscess remains less clearly established. Underlying immunocompromising conditions, including diabetes and smoking, frequently contribute to disease development. Similar inflammatory mechanisms can occur, beginning with ductal inflammation, progressing to fluid collection, and culminating in infection. Skin trauma, including trauma associated with nipple piercings, may also contribute. Nonlactational abscesses more commonly occur in subareolar or periareolar locations compared to peripheral breast tissue.[25]

Smoking contributes to breast abscess pathogenesis through both immunosuppressive effects and the potential for tobacco toxins to damage lactiferous ducts. Smoking has a strong association with periductal mastitis accompanied by squamous metaplasia of the lactiferous ducts, a condition known as Zuska disease. During this process, the normal cuboidal epithelium of the terminal ducts undergoes squamous metaplasia, resulting in keratin accumulation and subsequent luminal obstruction.[26] Bacterial infection can subsequently develop, and fistula formation may occur. This pathophysiologic process may help explain the strong association between smoking and breast abscess formation, although additional research remains necessary.[3]

Histopathology

Histopathology can be especially useful in evaluating a nonlactating breast abscess, though biopsy is not always necessary. Importantly, histopathologic examination can rule out underlying malignancy and may uncover an undiagnosed underlying condition, eg, idiopathic granulomatous mastitis.[25][27] If a biopsy of a breast abscess is performed, histopathology typically demonstrates a mixed, predominantly neutrophilic inflammatory infiltrate (see Image. Breast Abscess Inflammatory Infiltration). In lactation, lactational changes, including dilated ducts and secretory epithelium, can be seen. During the healing process, histopathologic findings of neutrophilic inflammation are replaced by chronic inflammatory changes and granulation tissue. In nonlactational subareolar abscesses, dilated ducts with squamous metaplasia of the lactiferous ducts with keratin plugging may be seen.[28]

History and Physical

Clinical History

Patients with a breast abscess typically present with progressive unilateral breast pain, erythema, induration, warmth, and fluctuance, with a palpable mass also possible. Systemic manifestations may include malaise, fever, chills, body aches, fatigue, nausea, and vomiting.

A thorough history should document symptom duration, the presence of pain or a palpable mass, skin thickening, changes in symptoms over time, and the location, color, and amount of any nipple discharge. Clinicians should determine whether the patient is breastfeeding and, if so, for how long, as well as whether the patient is pregnant or could be pregnant. The history should also identify previous breast infections, prior treatments, eg, incision and drainage or aspiration, and any cosmetic or plastic surgery procedures. A comprehensive medical, surgical, and social history should include assessment of diabetes and tobacco use. Breast cancer risk factors, including family history, should also be identified.[29]

Physical Examination

Following the history, clinicians should perform a focused physical examination. Visual inspection should assess breast size and symmetry, skin changes (eg, erythema, edema, or peau d’orange), areas of skin bulging or retraction, changes involving the nipple-areolar complex, and visible nipple discharge (see Images.  Breast Abscess and Peau D'Orange). Palpation should include both breasts and the axillary and supraclavicular lymph nodes. Breast examinations most commonly occur with the patient supine, although some experts recommend palpation in both seated and supine positions. Clinicians should characterize any palpable mass by documenting its size, distance from the nipple-areolar complex, clock-position location, mobility, and presence of any erythema, fluctuance, or tenderness. A mass, for example, may be documented as a “3-centimeter (cm), well-circumscribed fluctuant mass in the left breast at 12 o’clock with limited mobility, 2 cm from the nipple-areolar complex, exquisitely tender to palpation with surrounding erythema.”[29] Vital signs should also be recorded, with particular attention to fever and tachycardia.

Evaluation

Initial Diagnostic Testing

The physical examination serves as the cornerstone of breast abscess diagnosis. A complete blood count (CBC) may be obtained to assess for leukocytosis. When frank drainage occurs, clinicians should obtain cultures to guide antibiotic selection and subsequent treatment. Ultrasound represents the preferred imaging modality for evaluating a suspected breast abscess. Breast ultrasound can distinguish mastitis or cellulitis from a drainable abscess. Ultrasound can also help guide drainage by defining the abscess size and location and identifying any loculations. On ultrasound, breast abscesses may appear as hypoechoic fluid collections containing internal debris, septations, and irregular borders.

Breast Abscess Biopsy

In selected cases, needle aspiration can confirm a breast abscess, with subsequent analysis of the aspirated fluid. When a suspected breast abscess fails to improve within 7 to 10 days of empiric treatment, clinicians should pursue additional diagnostic evaluation to exclude malignancy. A palpable mass or skin changes concerning for inflammatory breast cancer, including peau d’orange, warrant core needle biopsy. For patients without a palpable mass, diagnostic mammography should be considered to evaluate for an underlying malignancy, particularly among patients older than 30 years. Depending on clinical and imaging findings, tissue diagnosis may involve fine-needle aspiration, core needle biopsy, or excisional biopsy.[29] For nonlactational breast abscesses, clinicians should consider screening for diabetes and HIV according to the individual clinical scenario.

Treatment / Management

As with abscesses elsewhere on the body, local source control is the mainstay of treatment for breast abscesses.[Surgical Oncology Insight. Society of Surgical Oncology Medical Student and Trainee Primer for Breast Surgical Oncology. 2025] While antibiotics are generally sufficient to treat bacterial mastitis, and may be sufficient for small abscesses identified early, antibiotic penetration into a large abscess is limited.[30] Historically, incision and drainage has been the treatment of choice. Recent evidence supports needle aspiration as a viable treatment option.[30][31](A1)

A 2023 meta-analysis evaluated 9 randomized controlled trials involving 703 patients and compared needle aspiration with incision and drainage for the treatment of breast abscesses. Of the 9 trials, 2 included both lactational and nonlactational abscesses, while 7 included lactational abscesses exclusively. The analysis found no significant differences in cure or recurrence rates between treatment groups. Ultrasound guidance during needle aspiration also did not significantly affect treatment outcomes. However, needle aspiration provided several advantages, including a shorter healing time of 11.02 fewer days, a lower rate of breastfeeding interruption (relative risk, 0.28), a lower incidence of fistula formation (relative risk, 0.21), and greater satisfaction with breast appearance (relative risk, 1.51).[31] Across the studies, mean abscess diameter ranged from 3 cm to 7.9 cm, with some trials reporting maximum abscess diameters of 3 cm or 5 cm.(A1)

Factors associated with needle aspiration failure include multilocular abscesses and abscesses larger than 5 cm. Abscesses smaller than 3 cm have a high likelihood of healing after a single aspiration. Some abscesses require multiple aspirations, ranging from 1 to 5 procedures, or subsequent incision and drainage.[31] A retrospective study associated smoking and nipple piercing with the need for repeat procedures.[32] Several clinical trials evaluating breast abscess management remain ongoing (see Table 1).[ClinicalTrials.gov. Breast Abscess](A1)

Although needle aspiration provides an appropriate treatment option for many patients, incision and drainage should be considered for large-volume or multicompartmental abscesses and for abscesses that fail needle aspiration.[31] Expert consensus from the American Society of Breast Surgeons, the Society of Breast Imaging, and the College of American Pathologists supports aspiration for lactational fluid collections smaller than 3 cm and does not recommend serial aspiration. For lactational abscesses or fluid collections larger than 3 cm, or when initial aspiration fails, the consensus recommends a stab incision using an 11-blade. Loculations can be disrupted with an instrument, eg, a hemostat. Gravity drainage with a one-fourth-inch Penrose, Foley, or seroma catheter for 3 to 5 days is recommended, and the drained material should be cultured. The incision site may leak milk but should gradually close. Patients should continue breastfeeding or pumping at physiologic volumes that do not exceed the infant’s intake. Pumping should be avoided only when the process would traumatize the drainage site. Patients should avoid squeezing the drainage site or attempting to express its contents. Persistent milk fistula remains uncommon, with a complication rate below 2%.[26](A1)

For nonlactational subareolar breast abscesses measuring 3 to 5 cm, an initial aspiration attempt is recommended. Abscesses associated with thin or attenuated overlying skin, those larger than 5 cm, and those that fail serial aspiration should undergo incision and drainage. Drain placement or packing generally remains unnecessary in these circumstances. When a drain is placed, the previously described drainage guidance applies.[26] When readily available, ultrasound should be used for diagnosis and drainage guidance. If ultrasound cannot be obtained, clinicians can perform aspiration or drainage without imaging.[26]

Needle aspiration and many incision-and-drainage procedures can be performed under local anesthesia in an outpatient setting. Patients who cannot tolerate an office-based procedure, those with very large abscesses or heavily loculated collections, and those with abscesses containing solid components may require incision and drainage in the operating room. When overlying skin necrosis occurs, the affected skin should be excised. The incision should remain as small as feasible while providing adequate drainage and should be positioned as far from the nipple-areolar complex as possible. Wound packing is not recommended. Drain placement promotes continued drainage and prevents premature closure of the skin incision before the abscess has adequately drained.[26]

Healing time varies according to abscess size and patient-specific factors. Small abscesses may heal within days to a week, whereas larger abscesses may require 4 to 6 weeks for complete healing. Diabetes and smoking can prolong the healing process. For recurrent abscesses, particularly subareolar nonlactational breast abscesses, surgical excision of the affected lactiferous ducts may be considered.[33] Squamous metaplasia can promote keratin accumulation and recurrent infection when ductal obstruction develops. Total duct excision generally provides curative treatment and can be considered after at least one recurrence or whenever a persistent fistula develops.[26][ABS. Pesce and Yao. Abscess/Infections/Periareolar Mastitis. 2021]

Antibiotics

Culture and Gram stain results obtained during aspiration or incision and drainage should guide antimicrobial selection, particularly for recurrent abscesses. For lactational abscesses and abscesses occurring during pregnancy, dicloxacillin or cephalexin is generally the first-line empiric option. Patients with MRSA risk factors or beta-lactam hypersensitivity can receive trimethoprim-sulfamethoxazole or clindamycin. Nonlactational breast abscesses more frequently involve mixed and gram-negative organisms, making amoxicillin-clavulanate or metronidazole combined with dicloxacillin or cephalexin appropriate options.[30] Antibiotic treatment following needle aspiration or incision and drainage commonly continues for 10 to 14 days.

Trimethoprim-sulfamethoxazole should be avoided in patients breastfeeding infants younger than 8 weeks, premature infants, jaundiced infants, ill infants, or infants with glucose-6-phosphate dehydrogenase (G6PD) deficiency because of the risk of hyperbilirubinemia and kernicterus. Clinicians generally avoid trimethoprim-sulfamethoxazole during pregnancy, particularly during the first trimester and near delivery. Hemodynamically unstable patients or those with sepsis requiring hospitalization generally receive intravenous vancomycin as first-line therapy. Other intravenous options include clindamycin, while linezolid may be considered for refractory infections. The attached antibiotic choice flowchart provides commonly used doses. An obstetrician-gynecologist should be consulted whenever concerns arise regarding antibiotic safety during pregnancy or lactation.

Pain Control and Breastfeeding Recommendations

Pain management should include consideration of nonsteroidal anti-inflammatory drugs (NSAIDs) and prescription narcotics when clinically appropriate. Cold therapy remains preferable to heat for reducing breast inflammation. Patients should continue breastfeeding from the affected breast whenever possible. Breastfeeding or pumping should occur at physiologic volumes and should not exceed the amount of milk consumed by the infant.

Table 1. Ongoing Clinical Trials Regarding Treatment and Management of Breast Abscess 

Differential Diagnosis

The most important differential diagnosis to rule out is malignancy, including inflammatory breast cancer, which is rare but extremely aggressive. This is especially true for nonlactating breast abscesses, those with atypical presentations, and those not responding to treatment for abscess (see Table 2). 

 Table 2. Differential Diagnoses of Breast Abscesses

Prognosis

The majority of isolated breast abscess cases have good outcomes. Healing time can range from 1 to 6 weeks after treatment, with larger abscesses taking longer to heal. Most breast abscesses can be managed in the outpatient setting; however, up to 20% of patients may need hospitalization, most often for intravenous antibiotics.[41][42] The average hospital length of stay is 2 to 3 days.[18] Many individuals can continue breastfeeding. In one study, about one-third stopped breastfeeding within 3 months, the average duration was 5 months, and 40% breastfed for 6 months or longer.[41]

Lactational breast abscesses generally have higher cure rates and lower risk of recurrence. Some studies report no recurrence of lactational breast abscess.[3] In one study of breast abscess recurrence, only 7% were lactational.[7] Conversely, recurrence rates in nonlactational breast abscesses can be as high as 40% to 57%.[3][7] The most significant risk factor in multivariate analyses is tobacco smoking, with an odds ratio of 14.73 in one study.[3][7] Patients with recurrence are more likely to have mixed bacterial and anaerobic infections.[3] Interestingly, in some studies, patients with recurrence were less likely to have MRSA infections.[3][7] Up to 50% of individuals with nonlactational breast abscess, especially subareolar, will require surgical excision of affected ducts, which is usually curative.[43]

Complications

Complications associated with breast abscesses include:

• Breast asymmetry
• Fistula
• Impact on future lactation/breastfeeding
• Pain
• Recurrence, need for additional procedure 
• Retraction of nipple-areolar complex 
• Scarring, cosmetic deformity 
• Sepsis 

Incision and drainage may result in unfavorable cosmetic outcomes, including scarring and breast asymmetry. Fistula formation can occur during the healing process and may cause milk to drain through the skin. In severe cases, tissue injury associated with infection or surgical intervention may compromise future lactation capacity. Patients who qualify for needle aspiration may experience a shorter healing time, lower incidence of fistula formation, less interruption of breastfeeding, and greater satisfaction with breast appearance compared with patients managed with incision and drainage.[31] (Please refer to the Treatment/Management section for more information.)

Breast abscesses rarely progress to severe or life-threatening infections, including sepsis, although increased risk is associated with delayed treatment and immunosuppression. Persistent symptoms after 4 weeks of empiric treatment warrant evaluation for malignancy with core needle biopsy.

Breast Abscess and Malignancy

A 10-year retrospective study found biopsy-proven malignancy in 4.4% of breast abscess cases, underscoring the importance of assessing breast cancer risk and ensuring appropriate screening.[44] Although available evidence has not established a causal relationship, several epidemiologic studies have identified a modest association between mastitis or breast abscess and subsequent breast cancer risk. The association appeared stronger among postmenopausal individuals. These studies did not account for all recognized confounding factors, including smoking, diet, and parity.[45][46][47][48] Chronic inflammation leading to genomic instability and subsequent mutations represents a possible mechanism underlying the observed association between mastitis or breast abscess and breast cancer. Additional research remains necessary to clarify the relationship between breast mastitis, breast abscess, and subsequent malignancy risk.