INTRODUCTION — A breast abscess is a localized collection of inflammatory exudate (ie, pus) in the breast tissue. Breast abscesses develop most commonly when mastitis or cellulitis does not respond to antibiotic treatment, but an abscess can also be the first presentation of breast infection. It is an uncommon problem in breastfeeding with a reported incidence of 0.1 percent ; the incidence among women with antibiotic-treated mastitis is 3 percent . Breast abscess can develop de novo (ie, primary; no inciting disease) or it can occur as a complication of another disease process (ie, secondary) such as periductal mastitis, skin infection over the breast, or granulomatous lobular mastitis.
Issues related to primary breast abscess will be reviewed here. Issues related to mastitis, cellulitis, and postoperative complications of breast surgery are discussed separately. (See "Lactational mastitis" and "Nonlactational mastitis in adults" and "Breast cellulitis and other skin disorders of the breast" and "Mastectomy", section on 'Complications' and "Breast-conserving therapy", section on 'Complications'.)
ETIOLOGY AND RISK FACTORS — Primary breast abscesses develop as a complication of mastitis . In a review of 89 patients with primary breast abscesses requiring surgical intervention, 14 percent were complications of lactational mastitis and 86 percent were complications of nonlactational mastitis . The incidence of breast abscesses ranges from 0.4 to 11 percent of lactating mothers . Breast abscesses in nonlactating women occurred more commonly in African Americans, obese patients, and smokers.
Risk factors for development of breast abscess as a complication of lactational mastitis include maternal age >30 years, first pregnancy, gestational age ≥41 weeks, and tobacco use [1,5,6]. Risk factors for a staphylococcal abscess in lactating mothers in one study identified problems with breastfeeding (odds ratio 5.0) and being a mother employed outside her home (odds ratio 2.74) as risk factors .
In a retrospective study of 68 patients all with breast abscess, smoking was a significant risk factor for the development of an abscess (odds ratio 8.0, 95% CI 3.4-19.4) . Of the 68 cases, over half (54 percent) needed multiple surgical treatments and 22 of these were heavy smokers. Five patients developed fistulas and all were heavy smokers. In another retrospective study of 89 patients with any type of breast abscess, 39 women (43 percent) were heavy smokers . The majority of patients who developed recurrent abscesses were smokers (77 percent). Smoking was the only factor significantly associated with abscess recurrence.
Nonlactational abscesses may be classified as central, peripheral, or skin associated (figure 1). Central abscesses are usually due to periductal mastitis. Peripheral abscesses are less common than central abscesses and are sometimes associated with underlying disease states such as diabetes, rheumatoid arthritis, steroid treatment, and trauma. (See "Nonlactational mastitis in adults", section on 'Periductal mastitis'.)
MICROBIOLOGY — Most primary breast abscesses are caused by Staphylococcus aureus. Methicillin-resistant S. aureus (MRSA) is becoming an increasingly important pathogen in cases of lactational and nonlactational mastitis . As an example, in one report, MRSA accounted for 12 percent of lactational abscesses and 8 percent of nonlactational abscesses . Risk factors for MRSA are summarized in the following table (table 1).
Less frequent pathogens include Streptococcus pyogenes, Escherichia coli, Bacteroides species, Corynebacterium species, coagulase-negative staphylococci (eg, S. lugdunensis), Pseudomonas aeruginosa, Proteus mirabilis, and anaerobes .
Patients with recurrent breast abscess have an increased incidence of mixed flora and anaerobic infection .
CLINICAL FEATURES AND DIAGNOSIS — Patients with primary breast abscess present with localized, painful inflammation of the breast associated with fever and malaise, along with a fluctuant, tender, palpable mass. The time course is variable; mastitis and abscess may present concurrently or abscess may develop 5 to 28 days following treatment for mastitis .
The diagnosis of breast abscess should be suspected based on clinical manifestations (localized inflammation of the breast associated with fever and a fluctuant, tender, palpable mass). The diagnosis may be confirmed via ultrasonography demonstrating a fluid collection [11-13]. Ultrasound imaging may be used for guided aspiration of the collection (image 1) .
For women who are lactating, culture of the breast milk is useful to guide selection of antibiotics if an aspirate is not obtained or does not demonstrate pus; culture is particularly important in the setting of infection that is severe, hospital acquired, or unresponsive to initial antibiotics [14,15].
Blood cultures are warranted in the setting of severe infection (eg, hemodynamic instability, progressive erythema) but are otherwise not routinely necessary.
DIFFERENTIAL DIAGNOSIS — The differential diagnosis of breast abscess includes:
●In lactating women:
•Plugged duct – A plugged duct is a localized area of milk stasis within the milk duct that causes distention of mammary tissue. Symptoms include a palpable lump with tenderness. A plugged duct may be distinguished from mastitis and breast abscess by the absence of systemic findings. (See "Common problems of breastfeeding and weaning", section on 'Plugged ducts'.)
•Galactocele – A galactocele (also known as a milk retention cyst) is a cystic collection of fluid that is usually caused by an obstructed milk duct. Galactoceles present as soft cystic masses; they are not tender and are not associated with systemic manifestations. Ultrasonography may demonstrate a simple milk cyst or a complex mass. The diagnosis can be made on the basis of the clinical history and needle aspiration, which yields a milky substance. (See "Common problems of breastfeeding and weaning", section on 'Galactoceles'.)
●In any women with an abscess:
•Inflammatory breast cancer – Inflammatory breast cancer should be considered if a breast infection does not resolve with appropriate treatment. Clinical manifestations include skin thickening due to edema, erythema, and peau d'orange appearance (picture 1). It is often associated with axillary lymphadenopathy. The diagnosis is established via biopsy. (See "Inflammatory breast cancer: Clinical features and treatment".)
TREATMENT — Management of primary breast abscess consists of drainage and antibiotic therapy [3,11,12,16-18].
Drainage — Options for breast drainage include needle aspiration and surgical drainage .
The clinical approach depends in part on the state of the overlying skin (figure 2). Aspiration of the abscess under ultrasound guidance using local anesthesia is the preferred method of management if the overlying skin is not ischemic (see 'Needle aspiration' below) [11-13,18]. If the overlying skin is compromised (eg, ischemia or pressure necrosis of the skin), or in cases in which the abscess is not responsive to needle aspiration and antibiotic therapy, surgical drainage will be required [20,21]. (See 'Surgical drainage' below.)
Male breast abscesses are treated similarly, via aspiration or incision and drainage under local anesthetic (picture 2).
Needle aspiration — Needle aspiration is an appropriate initial approach for abscess drainage when the overlying skin is normal (ie, erythematous but not ischemic) [22-25]. The use of ultrasound guidance ensures complete drainage and facilitates aspiration of loculated areas as well as collections that may not be appreciated on physical exam. Needle aspiration should be repeated every two or three days until no collection remains. Two to three aspirations are sufficient in many cases, although larger collections may require up to six aspirations (figure 2).
Infiltration and irrigation with local anesthetic reduces pain; use of epinephrine reduces subsequent bleeding and bruising. Local anesthetic is infiltrated via a puncture site positioned a few centimeters away from the abscess. One percent lidocaine with 1:200,000 epinephrine at a maximum dose of 7 mg/kg is injected into the skin and through the breast tissue to the edge of the abscess cavity using a 21-gauge needle. If the visible pus is not particularly thick, it can be aspirated with the same needle. Aspirated material should be sent for culture. Once the pus is aspirated, the syringe is changed and the abscess cavity is lavaged with the same local anesthetic. Irrigation with local anesthetic to dilute the pus is continued until all the pus is aspirated and the aspirate from the cavity comes back clear.
If the pus is thick, local anesthetic is injected gently into the abscess cavity and aspiration is attempted. If the pus cannot be aspirated, remove the syringe and needle. After waiting for the local anesthetic and epinephrine to take effect (at least seven or eight minutes), a 19- or 17-gauge needle is advanced along the anesthetized track into the cavity to wash the abscess with local anesthetic and dilute the pus. Over 40 mL of local anesthetic can be used safely in most adults (and up to 50 mL in a patient that weighs just over 70 kg). Larger volumes are safe providing that the local anesthetic that is irrigated into the cavity is later aspirated. However, too much local anesthetic injected into the abscess cavity increases the pressure in the abscess and can be painful. (See "Subcutaneous infiltration of local anesthetics" and "Local anesthetic systemic toxicity".)
The patient should be re-examined every two to three days and the cavity imaged with ultrasound and aspiration repeated in a similar manner until there is no further fluid visible in the abscess cavity or the fluid aspirated is serous [11,12,18].
The usual sequence is that, at the second aspiration, the pus is thinner and it subsequently turns to serous fluid. Few abscesses require more than two or three aspirations. The majority of lactating breast abscesses can be managed in this manner (picture 3).
For cases in which the abscess is unresponsive to the combination of repeated drainage and antibiotics, surgical intervention is indicated.
An option to recurrent aspiration is to place a pigtail catheter into the abscess under ultrasound guidance. In a study of 34 patients, this produced resolution in all and appears a safe option to repeated aspiration . The catheter must remain in the breast for a few days.
Surgical drainage — Surgical mini incision and drainage is warranted in the setting of overlying skin ischemia (picture 4A-D and figure 3 and picture 5) or pressure necrosis (picture 4B), and for cases in which the abscess is not responsive to needle aspiration or catheter drainage and antibiotics [20,21]. In addition, incision and drainage is appropriate if the skin overlying the abscess is very thin and shiny (picture 4A-D and figure 3 and picture 5), if it appears that the abscess is about to burst through the skin, or if the overlying skin is necrotic (picture 4B and figure 2).
Incision and drainage can be performed with local anesthesia in most cases in the office or outpatient clinic [20,21]. If the skin is very thin, it is infiltrated with 1 percent lidocaine with 1:200,000 epinephrine. Care should be taken not to inject too much local anesthetic into the abscess cavity prior to drainage, as this increases pressure in the abscess and in the office causes pain.
Following adequate local anesthesia, a small stab incision should be made through the thinned skin and pus drained. The abscess cavity should then be irrigated with local anesthetic and epinephrine solution until all the pus is evacuated. Abscess material should be sent for culture. The patient should be re-examined every two or three days until the wound closes and no further pus is visible either on direct inspection or on ultrasound.
In the setting of skin necrosis overlying the abscess, the necrotic skin should be excised and the cavity irrigated with local anesthetic and epinephrine solution to drain the pus. The abscess cavity should then inspected every two or three days and irrigated as appropriate.
Large incisions are not necessary to drain breast abscesses. An incision over an abscess does not need to be dependent. In our experience, drains or packing are not necessary [11,12].
In a randomized trial of 45 patients with lactational abscess, 40 percent of the patients treated with needle aspiration required subsequent incision and drainage . In the patients randomized to incision and drainage, 70 percent were unhappy with the cosmetic appearance. In another study of 50 patients with abscesses (including 31 who were lactating), aspiration alone was successful in 39 (78 percent) . Risk factors for failure of needle aspiration included abscess >5 cm in diameter, unusually large volume of aspirated pus, and delay in treatment.
Antibiotics — Empiric antibiotic therapy for primary breast abscess should include activity against S. aureus; therapy should be tailored to results of Gram stain and culture results when available.
●In the setting of nonsevere infection in the absence of risk factors for methicillin-resistant S. aureus (MRSA), outpatient therapy may be initiated with dicloxacillin (500 mg orally four times daily) or cephalexin (500 mg orally four times daily), pending culture results . In the setting of beta-lactam hypersensitivity, clindamycin (300 to 450 mg orally three times daily) may be used.
●In the setting of nonsevere infection with risk for MRSA (table 1), outpatient therapy with trimethoprim-sulfamethoxazole (1 to 2 tabs orally twice daily) or clindamycin (300 to 450 mg orally three times daily) may be initiated.
●In the setting of severe infection (eg, hemodynamic instability, progressive erythema), empiric inpatient therapy with vancomycin (table 2) should be initiated; therapy should be tailored to culture and sensitivity results. Gram stain results demonstrating gram-negative rods should prompt empiric antibiotic therapy against these organisms with a third-generation cephalosporin or a combination beta-lactam–beta-lactamase agent.
The presence of a subareolar breast abscess with a retracted nipple or a breast abscess associated with hidradenitis suppurativa should raise the possibility of anaerobic infection, and coverage for anaerobes should be included in the antibiotic regimen; options include use of amoxicillin-clavulanic acid (in the absence of MRSA), clindamycin, or dicloxacillin with the addition of metronidazole .
The optimal length of antibiotic therapy is not certain; 10 to 14 days following drainage is likely appropriate.
ROLE OF BREASTFEEDING — In the setting of lactational infection, milk drainage (either by breastfeeding or pumping) is important for resolution of infection and relief of discomfort [11,15,28]. One randomized trial of lactational infection noted that emptying of the breast resulted in reduction in the duration of symptoms and improved outcome .
A breast abscess or infection associated with prior lactation is not a contraindication to subsequent breastfeeding. Women should be encouraged to continue breastfeeding following breast infection, even in the setting of incision and drainage. If there is difficulty with breastfeeding because the incision interferes with nursing on the affected breast, the infant cannot relieve breast fullness, or the mother is too unwell to continue feeding, then it may be appropriate to advise stopping breast feeding. If the woman wants to continue to breast feed despite these issues, hand expression or breast pumping can be effective for maintaining the milk supply until breastfeeding can resume. Nursing should continue on the unaffected breast.
COMPLICATIONS — Complications include recurrent infection, poor cosmetic outcome, mammary duct fistula, milk fistula, and antibioma. Recurrent infection is more common in the setting of nonlactational abscess, diabetes, and tobacco use . Cosmetic outcome is more likely to be poor in the setting of delayed treatment (picture 6).
Mammary duct fistula — A mammary duct fistula is a communication between a major subareolar duct and the skin, usually in the periareolar region (picture 7A-D) . It can occur after incision and drainage of a central breast abscess caused by periductal mastitis or it can occur after spontaneous drainage of a periareolar inflammatory mass. (See "Nonlactational mastitis in adults", section on 'Subareolar abscess and periareolar fistula'.)
Patients who develop mammary duct fistula usually have a history of recurrent periareolar inflammation, including recurrent abscess formation, as well as a history of tobacco use [11,12,32]. Occasionally there is more than one external opening at the areolar margin and this can be from a single duct or multiple ducts.
Milk fistula — A milk fistula is a tract between the skin and a lactiferous duct associated with surgical intervention for a breast abscess while a woman is lactating, resulting in milk draining through the skin of the breast [33,34]. Development of a milk fistula is rare in the setting of aspiration or mini-incision and drainage and occurs more commonly in the setting of extensive surgical drainage with placement of large drains (which is rarely necessary).
A milk fistula usually resolves spontaneously; if persistent, it usually resolves with cessation of lactation. The baby can be weaned from the involved breast and continue to nurse from the other breast; this requires assistance from a lactation specialist in most cases. (See "Common problems of breastfeeding and weaning".)
Antibioma — If a breast abscess is treated with antibiotics in the absence of drainage, localized pus may become sterile with a thick fibrous tissue cover. This condition is known as an antibioma; it manifests as a smooth, firm, painless swelling.
This may be treated in a similar manner to other breast abscesses with aspiration but can take longer to resolve. Excision is not warranted and may delay wound healing.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Evaluation of breast problems".)
SUMMARY AND RECOMMENDATIONS
●A breast abscess is a localized collection of pus in the breast tissue. Primary breast abscesses develop when mastitis does not respond to antibiotic treatment. (See 'Introduction' above.)
●Most primary breast abscesses are caused by Staphylococcus aureus. Methicillin-resistant S. aureus infections are increasingly common. Patients with recurrent breast abscess have an increased incidence of mixed flora and anaerobic infection. (See 'Microbiology' above.)
●Management of primary breast abscess consists of drainage and antibiotic therapy. (See 'Treatment' above.)
●We suggest that initial drainage be performed by needle aspiration with ultrasound guidance (Grade 2C). Surgical drainage is indicated for patients who present with compromise of the overlying skin and for patients who do not respond to aspiration (figure 2). (See 'Drainage' above.)
●Empiric antibiotic therapy for primary breast abscess should include activity against S. aureus; therapy should be tailored to results of Gram stain and cultures results when available. (See 'Antibiotics' above.)
●In the setting of lactational infection, milk drainage (either by breastfeeding or pumping) is important for resolution of infection and relief of discomfort. Women should be encouraged to continue breastfeeding following breast infection. (See 'Role of breastfeeding' above.)
●We suggest that breastfeeding continue during treatment for lactation-associated breast infections (Grade 2C). If there is difficulty with breastfeeding, hand expression or breast pumping can be effective for maintaining the milk supply until nursing can resume. (See 'Role of breastfeeding' above.)