Differential Diagnosis for an 11-Day-Old with a Breast Lump

Single Most Likely Diagnosis

• Neonatal Breast Hypertrophy: This condition is common in newborns due to the influence of maternal hormones. It can cause breast tissue to become enlarged, sometimes forming a noticeable lump. This condition is usually benign and resolves on its own.

Other Likely Diagnoses

• Breast Cyst or Abscess: Though less common, a breast cyst or abscess can occur in neonates. These are usually related to infection or blockage of the milk ducts and can present as a lump.
• Milk Retention Cyst: Similar to a breast cyst, a milk retention cyst can form if there is an obstruction in the ducts, leading to the accumulation of milk and causing a lump.

Do Not Miss Diagnoses

• Breast Tumor (e.g., Fibroadenoma, though extremely rare in neonates): Although exceedingly rare, any lump in a neonate warrants consideration of a tumor to ensure early detection and treatment if necessary.
• Infectious Process (e.g., Mastitis): An infection of the breast tissue can present as a lump and is a critical diagnosis not to miss due to the potential for serious complications if left untreated.

Rare Diagnoses

• Hematoma or Trauma: Though unlikely, a lump could be the result of trauma to the breast area, leading to a hematoma.
• Congenital Anomalies (e.g., Accessory Breast Tissue): Rarely, accessory breast tissue can be present and may become noticeable as a lump, especially if it becomes infected or inflamed.