Most common cause of bilateral breast enlargement in a newborn?
Most common benign cause of breast enlargement before age 8?
Premature thelarche
Most common breast mass in adolescents?
Fibroadenoma
First-line imaging for pediatric breast masses?
ultrasound !
What is the preferred biopsy technique in general for the breast?
core needle biopsy
Most common organism causing neonatal mastitis?
Staphylococcus aureus
Breast development plus pubic hair should make you think of...?
Precocious puberty: consult endo!
What benign male breast condition peaks around ages 13-14?
physiologic gynecomastia
Why isn't mammography routinely used?
dense breast tissue will decrease the sensitivity of the mammography
Two indications for biopsy
- rapid growth
- suspicious ultrasound
- persistent enlagement
- risk factors (prior malignancy, cancer predisposition syndromes Li fraumeni, cowden etc..)
Why should incision & drainage through the breast bud generally be avoided?
What imaging is first-line if diagnosis is uncertain?
US !
Name two ultrasound features of a fibroadenoma.
- Oval
- Well circumscribed
- hypoechoic
- mobile

When should MRI be considered?
Suspected malignancy or surgical planning
A 13-year-old girl has a 2.5 cm, well-circumscribed, mobile breast mass with classic fibroadenoma features on ultrasound. She has no risk factors and the lesion has been present for one month.
Observation and ultrasound follow-up in 6 months.
Pearl: Most pediatric fibroadenomas remain stable or regress, and unnecessary intervention risks cosmetic deformity and injury to the developing breast.
What ultrasound finding suggests a neonatal breast abscess?
A breast abscess requires drainage. What technique is preferred to minimize future cosmetic deformity: I&D or US guided aspiration?
ultrasound-guided aspiration is preferred rather than incision through the breast bud
What tumor can closely mimic a juvenile fibroadenoma?
Phyllodes tumor
About what percentage of pediatric breast ultrasounds are completely normal?
~52%
A 15-year-old undergoes core needle biopsy for a rapidly enlarging breast mass. Pathology returns fibroepithelial lesion

Surgical excision, because 25-35% of FELs are upgraded to phyllodes tumors after excision.
A newborn has bilateral breast enlargement without erythema or fever. Management?
Observation, likely neonatal breast hypertrophy!
Name one chest wall malignancy that can mimic a breast mass.
- Ewing sarcoma
- Rhabdomyosarcoma
- Lymphoma
What three findings should make you suspicious for phyllodes?
- rapid growth
- > 3 cm
- painless
- hard
- cleft-like cystic spaces on US
What imaging finding is most concerning for malignancy?
- irregular margins
- posterior shadowing
- non-parallel orientation
- complex solid/cystic lesion

A 14-year-old has a 5-cm rapidly enlarging breast mass. Ultrasound is suspicious for a phyllodes tumor. Core biopsy is inconclusive.
Excisional biopsy (wide local excision)