Mastitis

BASICS

DESCRIPTION

Mastitis is an inflammation of the breast parenchyma and possibly associated tissues (areola, nipple, subcutaneous [SC] fat).
Usually associated with bacterial infection (and milk stasis in the postpartum mother)
Can be lactational or nonlactational
Usually an acute condition but can become chronic cystic mastitis

EPIDEMIOLOGY

Predominantly affects females
Mostly in the puerperium; epidemic form rare in the age of reduced hospital stays for mothers and newborns
Neonatal form
Posttraumatic: ornamental nipple piercing increases risk of transmission of bacteria to deeper breast structures; Staphylococcus aureus is the predominant organism.

Incidence

3–20% of breastfeeding mothers develop nonepidemic mastitis, with greatest incidence among breastfeeding mothers 2 to 6 weeks postpartum.
Neonatal form occurs at 1 to 5 weeks of age, with equal gender risk and unilateral presentation.
Pediatric form occurs at or around or after puberty, with 82% of cases in girls.

ETIOLOGY AND PATHOPHYSIOLOGY

Microabscesses along milk ducts and surrounding tissues
Inflammatory cell infiltration of breast parenchyma and surrounding tissues
Nonpuerperal (infectious) S. aureus (including methicillin-resistant S. aureus [MRSA]), Bacteroides spp., Peptostreptococcus, Staphylococcus (coagulase negative), Enterococcus faecalis, Histoplasma capsulatum, Salmonella enterica, rare case of Actinomyces europaeus
Puerperal (infectious) S. aureus (including MRSA), Streptococcus pyogenes (group A or B), Enterobacteriaceae, Corynebacterium spp., Bacteroides spp., Staphylococcus (coagulase negative), Escherichia coli, Salmonella spp. (1)
Rare secondary site for tuberculosis in endemic areas (1% of mastitis cases in these areas): single breast nodule with mastalgia
Tuberculosis mastitis in nonendemic areas has also been reported in patients with exposure to TNF-α inhibitors and other immunomodulating compounds.
Corynebacterium sp. associated with greater risk for development of chronic cystic mastitis
Granulomatous mastitis
- Idiopathic: predilection for Asian and Hispanic women
  - Association with α₁-antitrypsin deficiency, hyperprolactinemia with galactorrhea, oral contraceptive use, Corynebacterium spp. infection, and breast trauma
  - Most women have a history of lactation in the previous 5 years.
  - New cases have been reported in male-to-female transgender patients in setting of exogenous progesterone and estrogen treatment.
- Lupus; autoimmune
Puerperal: Retrograde migration of surface bacteria up milk ducts, bacterial trapping behind plugged milk in the ductal outflow tracts. Bacterial migration from nipple fissures to breast lymphatics. Occasionally, secondary monilial infection in the face of recurrent mastitis or diabetes. Seeding from mother to neonate in cyclical fashion may occur.
Nonpuerperal: a variety of causes including ductal ectasia, breast carcinoma, inflammatory cysts, chronic recurring SC or subareolar infections, parasitic infections (Echinococcus, filariasis, guinea worm in endemic areas), herpes simplex, cat-scratch disease, and, in older patients, smoking. Lupus is a rare cause.

RISK FACTORS

Milk stasis: inadequate emptying of breast (scarring due to previous breast surgery [breast reduction, biopsy, or partial mastectomy], scarring of breast due to prior mastitis), breast engorgement: interruption of breastfeeding, milk oversupply, plugged ducts
Nipple trauma increases risk of transmission of bacteria to deeper breast structures: S. aureus predominant organism.
Neonatal colonization with epidemic Staphylococcus
Neonatal—occurs more commonly in bottle-fed babies.
Maternal diabetes
Maternal HIV
Smoking

GENERAL PREVENTION

Regular emptying of both breasts and nipple care to prevent fissures when breastfeeding; also good hygiene including hand washing and washing breast pumps after each use

COMMONLY ASSOCIATED CONDITIONS

Breast abscess

DIAGNOSIS

Fever >38.5°C, malaise, and myalgia
Nausea ± vomiting
Localized breast tenderness, firmness, heat, swelling, and redness
Possible breast mass

HISTORY

Breast pain, “hot cords burning in chest wall”

PHYSICAL EXAM

Breast tenderness
Localized breast induration, redness, and warmth
Peau d’orange appearance to overlying skin

DIFFERENTIAL DIAGNOSIS

Abscess (bacterial, idiopathic granulomatous mastitis, fungal, tuberculosis)
Tumor, including inflammatory breast cancer
Idiopathic granulomatous mastitis
Wegener granulomatosis
Sarcoidosis
Foreign-body granuloma
Vasospasm (may be presentation for Raynaud): Consider yeast infection if nipple pain and burning and/or infant with thrush.
Ductal cyst (ductal ectasia)
Consider monilial infection in lactating mother, especially if mastitis is recurrent.
Mondor disease—thrombophlebitis of the superficial veins of the breast and anterior chest wall

DIAGNOSTIC TESTS & INTERPRETATION

Initial Tests (lab, imaging)

Mastitis is typically a clinical diagnosis; labs rarely needed; in those ill enough to need hospitalization, consider the following:

CBC, blood culture
In epidemic puerperal mastitis: milk leukocyte count, milk culture (or if recurrent outpatient mastitis), neonatal nasal culture
No imaging required for postpartum mastitis in a breastfeeding mother that responds to antibiotic therapy
Mammography for women with nonpuerperal mastitis
Breast ultrasound (US) to rule out abscess formation in women with a mass or fluctuance on palpation; special consideration for this in women with breast implants who have mastitis

Follow-Up Tests & Special Considerations

Lactating mothers produce salty milk from affected side (higher Na and Cl concentrations) as compared with unaffected side. Consider breast milk culture if suspect MRSA. Also consider testing for tuberculosis as may be initial presentation.

Diagnostic Procedures/Other

Options if further progression to abscess formation: needle aspiration, incision and drainage, excisional biopsy, US-guided core needle biopsy is diagnostic method of choice for idiopathic granulomatous mastitis

TREATMENT

A Cochrane review found that insufficient evidence exists to confirm or refute the effectiveness of antibiotic therapy for the treatment of lactational mastitis (2)[A]. If present <24 hours and symptoms are mild, conservative management with milk removal and supportive measures is recommended.
For patients with early idiopathic granulomatous mastitis and mild symptoms or those concerned for surgical scarring, close surveillance or observation alone is acceptable nonsurgical management.

GENERAL MEASURES

Supportive care including analgesia, warm compress and effective, frequent milk removal from the affected breast via breastfeeding, pumping, or hand expression
Smoking cessation for patients with periductal mastitis

MEDICATION

Prioritized on the basis of likelihood of MRSA as etiologic factor and clinical severity of condition; treat for 10 to 14 days.
For idiopathic granulomatous mastitis and localized infection, usually resolves with antibiotics and drainage

First Line

Outpatient
- Effective milk removal is the most important management step.
- Dicloxacillin 500 mg QID or cephalexin 500 mg QID
- Trimethoprim/sulfamethoxazole (TMP/SMX); DS BID (If mastitis is not improving within 48 hours after starting first-line treatment, consider MRSA.)
- Doxycycline 100 mg BID; consider MRSA (if clinical course <3 weeks).
- Lactobacillus fermentum or Lactobacillus salivarius 9 log 10 CFU/day
Inpatient
- Nafcillin 2 g q4h or oxacillin 2 g q4h or vancomycin 1 g q12h (MRSA possible)
- Daptomycin 1 g q24h
If idiopathic granulomatous mastitis, consider corticosteroids ± methotrexate; may consider mycophenolate mofitel in patient refractory to treatment with antibiotics, steroids, and methotrexate

Pediatric Considerations

TMP/SMX given to breastfeeding mothers with mastitis can potentiate jaundice for neonates.
Treatment with doxycycline is limited to <3 weeks; long-term therapy (over 3 to 4 weeks) is not recommended because it may cause damage of infant’s growth cartilage, teeth discoloration, and imbalance of intestinal flora.

Second Line

If mastitis is odoriferous and localized under areola, add metronidazole 500 mg TID IV or PO.
If yeast is suspected in recurrent mastitis, add topical and oral nystatin. Consider testing nipple tissue and milk for presence of yeast. Oral treatment can be considered for mother as well.

ISSUES FOR REFERRAL

Abscess formation
Need for breast biopsy (suspected abscess or IGM)

ADDITIONAL THERAPIES

Warm packs to improve blood flow and milk letdown and/or ice packs to reduce inflammation to affected breast for comfort
The use of a breast pump may aid in breast emptying, especially if the infant is unable to assist in doing this.
Wear supporting bra that is not too tight.

SURGERY/OTHER PROCEDURES

In cases of biopsy-proven idiopathic granulomatous mastitis, the most effective and fastest way for complete eradication is surgical removal. The addition of steroids increases the rate of complete remission and decreases remission rate compared to surgery alone; NNT 3.84

COMPLEMENTARY & ALTERNATIVE MEDICINE

Breast lift technique for lymphatic breast drainage (can reduce engorgement and relieve plugging)
Cold cabbage leaf compress to be applied up to 15 minutes twice per day (Avoid long or frequent application of cabbage leaves as milk production can be diminished with this.)
To prevent recurring plugs and mastitis, can use sunflower lecithin 1,200 mg 3 to 4 times per day

ADMISSION, INPATIENT, AND NURSING CONSIDERATIONS

If a new mother is admitted to the hospital for treatment of her mastitis, rooming-in of the infant with the mother is highly recommended so that breastfeeding can continue. In some hospitals, rooming-in may require hospital admission of the infant.
Admission criteria/initial stabilization: Failure or outpatient/oral therapy (patient unable to tolerate oral therapy, non-adherent to oral therapy, or severe illness without adequate supportive care at home); neonatal mastitis also requires admission.
- Administer antibiotics.
- Empty breasts frequently, if breastfeeding.
- Give analgesics for pain: ibuprofen or acetaminophen.
- Breastfeeding/pumping of breasts encouraged; baby and/or breast pump to bedside
Start infant with feedings on affected side.
Abscess drainage is not a contraindication for breastfeeding.
Massage in direction from blocked area toward nipple.
Positioning the infant at breast with chin or nose pointing to blockage might help drain the affected area.
Discharge criteria: Patients should be afebrile and tolerating oral antibiotics well.

ONGOING CARE

FOLLOW-UP RECOMMENDATIONS

Patient Monitoring

Rest for lactating mothers, up to bathroom. Admit to medical floor. If concern for sepsis or hemodynamic instability, admit to intermediate level of care or ICU.
Follow up with breast imaging such as mammography or US in women >40 years of age after resolution of acute pathology to exclude underlying breast cancer.

DIET

Encourage oral fluids.
Multivitamin, including vitamin A

PATIENT EDUCATION

Encourage oral fluids. Rest is essential.
Regular emptying/draining of both breasts with breastfeeding
Nipple care (simply with breast milk or with hypoallergenic nipple balm) to prevent fissures
Best nipple/areola health comes with optimized latch—seek help with latch if needed from a lactation professional.

PROGNOSIS

Puerperal
- Good with prompt (within 24 hours of symptom onset) antibiotic treatment and breast emptying; 96% success rate
- 11% risk of abscess if left untreated with antibiotics
- Antibodies develop in breast glands within the first few days of infection, which may provide protection against infection or reinfection.
Rare risk of abscess formation beyond 6 weeks postpartum if no recurrent mastitis
Idiopathic granulomatous mastitis recurrence rates high, encourage close follow-up

COMPLICATIONS

Breast abscess 3% of women with puerperal mastitis, recurrent mastitis with resumption of breastfeeding or with breastfeeding after next pregnancy, cessation of breastfeeding, bacteremia, sepsis

Authors

Amena Payami, DO

REFERENCES

Wilson E, Woodd SL, Benova L. Incidence of and risk factors for lactational mastitis: a systematic review. J Hum Lact. 2020;36(4):673–686. [PMID:32286139]
Jahanfar S, Ng CJ, Teng CL. Antibiotics for mastitis in breastfeeding women. Cochrane Database Syst Rev. 2013;2013(2):CD005458. [PMID:23450563]

ADDITIONAL READING

Spencer JP. Management of mastitis in breastfeeding women. Am Fam Physician. 2008;78(6):727–731. [PMID:18819238]

CODES

ICD10

O91.11 Abscess of breast associated with pregnancy
O91.211 Nonpurulent mastitis associated with pregnancy, first trimester
O91.113 Abscess of breast associated with pregnancy, third trimester
N61 Inflammatory disorders of breast
O91.22 Nonpurulent mastitis associated with the puerperium
O91.23 Nonpurulent mastitis associated with lactation
N60.19 Diffuse cystic mastopathy of unspecified breast
N60.12 Diffuse cystic mastopathy of left breast
O91.219 Nonpurulent mastitis associated w pregnancy, unsp trimester
N60.11 Diffuse cystic mastopathy of right breast
P39.0 Neonatal infective mastitis
P83.4 Breast engorgement of newborn

SNOMED

45198002 Mastitis (disorder)
78697003 Nonpurulent mastitis associated with childbirth
82789004 Acute mastitis
83620003 Nonpuerperal mastitis
3468005 Neonatal infective mastitis
700038005 Mastitis associated with lactation (disorder)
47134002 Noninfective mastitis of newborn
21648003 Chronic mastitis

CLINICAL PEARLS

Emptying/draining of the breasts on a regular schedule (recommend following baby’s cues, but going no more than 3 to 4 hours between feeds), avoiding constrictive clothing or bras that might obstruct breast ducts, attention to good latch technique for mom and baby, “adequate rest,” and a liberal intake of oral fluids for the mother can all reduce the risk of a breastfeeding mother’s developing mastitis.
Reassure mothers that it is safe (and imperative for healing) to feed baby and/or pump the affected breast.
Among breastfeeding mothers, if the symptoms of mastitis fail to resolve within several days of appropriate management, including antibiotics, NSAID, and breast emptying, further investigations may be required to confirm resistant bacteria, abscess formation, an underlying mass, or inflammatory or ductal carcinoma.
More than two recurrences of mastitis in the same location or with associated axillary lymphadenopathy warrant evaluation with US and/or mammography to rule out an underlying mass.

Last Updated: 2026