Infections of the Breast

Clinical Presentation

Abscess of the breast usually results from rupture of mammary ducts often, but not always, with pregnancy and lactation. These abscesses present as swollen, often erythematous, and painful breast masses, which may simulate carcinoma. Lactation-related breast infection is most frequently seen within the first 6 weeks of breastfeeding, although some women have it with weaning, and the lactating infection presents with pain, swelling, and tenderness. There is usually a history of a cracked nipple or skin abrasion. S. aureus is the most common organism responsible, but Staphylococcus epidermidis and streptococci are occasionally cultured.

Gross Pathology

The typical abscess causes an edematous pink-red mass, which is cavitated centrally and filled with yellow viscous fluid (pus).

Microscopic Pathology

Breast tissue is displaced by chronic-active inflammation with numerous neutrophils, mixed with scattered plasma cells and histiocytes ( Fig. 3.1 ). Special stains may demonstrate causative organisms.

Treatment and Prognosis

All abscesses in the breast can be managed by repeated aspiration or incision and drainage. Few breast abscesses require drainage with the patient under general anesthesia, except those in children, and placement of a drain after incision and drainage is unnecessary. Better maternal and infant hygiene and early treatment with antibiotics have considerably reduced the incidence of abscess formation during lactation. Dener and Inan assessed contributing factors in developing puerperal breast abscess and evaluated the treatment options. During the 4-year study period, 128 nursing women with breast infection were followed. Of these, 102 (80%) had mastitis, and 26 (20%) had breast abscess. All patients with mastitis were treated with antibiotics, and none had an abscess. Ten abscesses were aspirated, and 16 abscesses were treated by incision and drainage. Healing times were similar. There was no significant difference between the mastitis and the abscess groups regarding age, parity, localization of breast infection, cracked nipples, positive milk cultures, or mean lactation time. Duration of symptoms and healing were longer in cases of abscess. Multivariate analyses showed that duration of symptoms was the only independent variable for abscess development. Recurrent mastitis developed in 13 (10.2%) patients within a median of 24 weeks of follow-up. The authors found that delayed treatment of mastitis can lead to abscess formation and that it can be prevented by early antibiotic therapy. Ultrasonography was helpful for detecting abscess formation, and in selected cases, the abscess can be drained with needle aspiration with excellent cosmesis.

Drainage of milk from the affected segment should be encouraged and is best achieved by continuing breastfeeding. Tetracycline, ciprofloxacin, and chloramphenicol should not be used to treat lactating breast infection because they may enter breast milk and can harm the baby. If the inflammation or an associated mass lesion still persists, further investigations are required to exclude an underlying carcinoma. An established abscess should be treated by either recurrent aspiration or incision and drainage. Many women wish to continue to breastfeed, and they should be encouraged to do so.

Differential Diagnosis

Putative abscesses that have solid areas or do not respond to therapy should be considered potential carcinomas, and tissue biopsy should be taken to rule out this possibility. Finally, not all that appear to be abscesses in these patient groups are abscesses. Galactoceles, noninfected milk-filled cysts, present as tender masses; aspiration is both diagnostic and curative. Benign fibroadenomas occasionally enlarge significantly or infarct during pregnancy. A physiological nipple discharge is common during pregnancy and may be bloody. Rare cases of massive breast hypertrophy during pregnancy have been reported. Death from breast cancer during pregnancy is related to delay in diagnosis: compared stage for stage with nonpregnant controls, the prognosis is similar. As a general rule, the cancer should be treated surgically, and the pregnancy may be allowed to progress.

One of the differential diagnoses is primary squamous cell carcinoma (SCC) of the breast, a rare neoplasm in this age group, with fewer than 100 cases reported in the English-language literature. However, primary breast SCC seems to have a propensity to mimic breast abscess, and these patients can be misdiagnosed and initially treated for breast abscess. There may be skin erythema associated with an underlying mass, and an infectious cause is often considered in these cases. These tumors unfortunately tend to be large (in the 4- to 5-cm range) and diagnosed at an advanced stage. For this reason, breast biopsy should be considered in cases of breast abscess, especially if there are any atypical features. Treatment of primary SCC of the breast is like that of more common types of breast cancer (i.e., breast conservation is possible and sentinel lymph node biopsy is recommended). Because metastasis to the breast from other primary tumor sites (lung, cervix, skin, and esophagus) has been reported, patients with pure SCC should undergo evaluation to exclude this possibility.

Clinical Presentation

Nonlactational infections can be separated into those occurring centrally in the periareolar region and those affecting the peripheral breast tissue. Periareolar infection is most commonly seen in women in their early 30 s.

Histologically, there is acute inflammation around nondilated subareolar breast ducts; a condition termed by some as periductal mastitis. This condition has been confused with and called duct ectasia, but duct ectasia is a separate condition affecting an older age group characterized by subareolar duct dilatation with less pronounced and mostly chronic (lymphocytic and histiocytic) periductal inflammation. Current evidence suggests that smoking is an important factor in the cause of periductal mastitis but not in duct ectasia. About 90% of women who get periductal mastitis or its complications smoke cigarettes compared with 38% of the same age group in the general population. Rare cases of subareolar breast abscess have been reported in male patients.

The importance of smoking was recently underscored in a study by Gollapalli and colleagues. This group investigated risk factors that predispose to the development of primary breast abscesses and subsequent recurrence. It was a case-control study of patients with a primary or recurrent breast abscess, with recurrence defined by the need for repeated drainage within 6 months. Sixty-eight patients with a primary breast abscess were identified. Univariate analysis indicated that smoking, obesity, diabetes mellitus, and nipple piercing were significant risk factors for development of primary breast abscess. Multivariate logistic regression analysis confirmed smoking as a significant risk factor for the development of primary breast abscess, and in the subtype of subareolar breast abscess, nipple piercing was identified as a risk factor in addition to smoking. Recurrent breast abscess occurred in 36 (53%) patients.

A second study points toward not only smoking but also other contributing factors. Bharat and associates investigated the patients’ and the microbiological risk factors that predispose to the development of primary breast abscesses and subsequent recurrence. Recurrent breast abscess was defined by the need for repeated drainage within 6 months. Patient characteristics were compared with the general population and between groups. A total of 89 patients with a primary breast abscess were identified; 12 (14%) were lactational and 77 (86%) were nonlactational. None of the lactational abscesses recurred, whereas 43 (57%) of the nonlactational abscesses did so. Compared with the general population, patients with a primary breast abscess were predominantly Black (64% versus 12%), had higher rates of obesity (body mass index >30: 43% versus 22%), and were tobacco smokers (45% versus 23%). The only factor significantly associated with recurrence in the multivariate logistic regression analysis was tobacco smoking. Compared with patients who did not have a recurrence, patients with recurrent breast abscesses had a higher incidence of mixed bacteria (20.5% versus 8.9%), anaerobes (4.5% versus 0%), and Proteus infection (9.1% versus 4.4%) but a lower incidence of Staphylococcus infection (4.6% versus 24.4%). Risk factors for development of a primary breast abscess include Black race, obesity, and tobacco smoking. Patients with recurrent breast abscesses are more likely to be smokers and have mixed bacterial and anaerobic infections. Broader antibiotic coverage should be considered for the higher-risk groups. Substances in cigarette smoke may either directly or indirectly damage the wall of the subareolar breast ducts. The damaged tissues then become infected by either aerobic or anaerobic organisms. Initial presentation may be with periareolar inflammation (with or without an associated mass) or with an established abscess. Associated features include central breast pain, nipple retraction at the site of the diseased duct, and nipple discharge.

Gross Pathology

The typical abscess causes an edematous pink-red mass, which is cavitated centrally and filled with yellow viscous fluid (pus). A mammary duct fistula is a communication between the skin, usually in the periareolar region and a major subareolar breast duct. A fistula can develop after incision and drainage of a nonlactational abscess, it can follow spontaneous discharge of a periareolar inflammatory mass, or it can result from biopsy of a periductal inflammatory mass. Treatment is by excision of the fistula and diseased duct or ducts under antibiotic cover. Recurrence is common after surgery, and the lowest rates of recurrence and best cosmetic results have been achieved in specialist breast units. Surgery performed through a circumareolar incision gives excellent cosmetic results.

Microscopic Pathology

Breast tissue is displaced by chronic-active inflammation with numerous neutrophils, mixed with scattered plasma cells and histiocytes. Special stains may demonstrate causative organisms.