• breastfeeding/lactation;
  • breast milk cultures;
  • breast pain;
  • Candida albicans;
  • etiology;
  • infection;
  • mammary candidosis;
  • mastitis;
  • nipple pain;
  • systematic reviews;
  • meta-analyses;
  • Staphylococcus aureus

Introduction: Controversy over the etiology of deep or burning breast pain during lactation continues to persist, despite a long history of published studies and case reports. This article reviews the literature exploring the etiology of deep breast pain, summarizes the results, and identifies possible explanations for the controversies surrounding this disorder.

Methods: A clinical query and a librarian-assisted search of MEDLINE were used to find articles published between 1896 and 2010. Inclusion criteria consisted of comparing microbial testing results from symptomatic and asymptomatic lactating women. Cases were restricted to those experiencing deep or burning breast pain when possible.

Results: Prospective studies consisting of 1 unmatched case-control and 6 cohorts were found. Trials typically detected higher microbial levels in the milk or nipple(s) or both of symptomatic women, irrespective of the detection method or type and range of microbes (bacterial, yeast, or fungal) studied. Case milk samples were positively associated with finding Staphylococcus aureus (relative risk ratio [RR] 7.29; 95% confidence interval [CI], 3.25-16.36) or Candida (RR 8.45; 95% CI, 3.96-18.06). Moreover, recent reports about small-colony variants and biofilm-producing organisms may explain the atypical symptoms unique to this disorder.

Discussion: In lactating women reporting deep breast pain, evidence consistent with infection is persistently found, and explanations exist for the disorder’s atypical characteristics. Although lactating women with deep breast pain are more likely to test positive for Candida, the risk of testing positive for S aureus is also present. Thus, these women should have cultures done. Management options include treating immediately while awaiting results or waiting until results are available to guide treatment. With either approach, providers must consider the risk of falsely negative tests.