Mammary glands in children: anatomy and functions

The formation of the mammary gland begins in the embryonic period: rudiments appear along the “milk line”, then the future tissue of the gland remains in the chest area, ducts and the rudiment of the nipple-areolar complex are formed. [1]

In newborns, breast tissue is often palpable in both sexes because it is influenced by maternal hormones and the subsequent decrease in their levels after birth, which can lead to temporary changes and even short-term secretion.[2]

In the first months of life, the baby may experience wave-like “hormonal activity”, after which the mammary gland usually enters a relatively calm period, which continues until the onset of puberty. [3]

Puberty in girls often begins with thelarche, that is, the appearance of the “chest bump” and the transition to stage 2 according to Tanner, and at the early stage the development can be one-sided and accompanied by moderate sensitivity. [4]

Table 1. Age stages and typical features

Period	What is often considered a normal variant	What should be a warning sign?
Newborn and first weeks	Engorgement under the nipple, short-term discharge, moderate asymmetry	Fever, bright redness, severe pain, fluctuation
Before puberty	No gland growth, rare short-term fluctuations in sensitivity	Steady breast growth up to age 8, growth acceleration, other signs of puberty
Puberty	Thelarche as the first sign, possible early asymmetry	A rapidly growing lump, skin changes, and bloody discharge

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The first year of life: engorgement, milky discharge, and how to avoid inflammation

Breast engorgement in infants is often associated with physiological hormonal changes after birth and often resolves on its own with careful care. [6]

Sometimes a milky discharge appears, and this is usually benign if there are no signs of infection and the baby is feeling well. [7]

A key practical point: squeezing and massage increase the risk of introducing bacteria and the physiological condition turning into mastitis or an abscess, so any attempts to “squeeze” are strictly undesirable. [8]

If fever, increasing redness, severe pain, or an area of softening develops, it no longer appears physiological and requires an in-person evaluation, often with ultrasound. [9]

Table 2. Physiological engorgement and mastitis: differences

Sign	More often a physiological condition	More often inflammation
General condition	No fever, the child is active	Often fever, lethargy
Leather	Without bright hyperemia	Bright redness, hot skin
Pain	Minimum	Severe pain
Palpation	A dense "knot" without fluctuation	Fluctuation is possible with an abscess
Tactics	Observation, hygiene	Urgent assessment and treatment

[10]

In prepubertal girls: precocious thelarche and how to distinguish it from true precocious puberty

Premature thelarche most often refers to the isolated appearance of a small amount of breast tissue without growth acceleration and without other signs of puberty, often before the age of 3 years.[11]

The main task of the doctor and the family is not to miss true precocious puberty, in which changes progress, adding accelerated growth, hair growth, changes in body odor and other signs of activation of the sexual axis. [12]

Key tools for discrimination are careful examination with Tanner staging, dynamic measurement of height and weight, and monitoring of the rate of change, because a single examination is sometimes insufficient.[13]

In isolated and stable thelarche, observation is often sufficient, but in case of progression, accelerated growth, or suspicion of hormonal causes, consultation with a pediatric endocrinologist and targeted examination are indicated. [14]

Table 3. Precocious thelarche and precocious puberty

Criterion	Premature thelarche	Precocious puberty
Breast growth	Often small and stable	More often progresses
Growth rate	Usually without acceleration	Often growth acceleration
Other signs	Usually absent	Additional symptoms often appear.
Tactics	Observation and dynamics	Endocrinologist, examination, treatment as indicated

[15]

In boys and adolescents: pubertal gynecomastia and when diagnosis of the causes is needed

Pubertal gynecomastia is a common benign condition in adolescents and is associated with a temporary imbalance between estrogen and androgen action during puberty.[16]

It typically presents with pain and swelling under the areola, often bilateral or asymmetrical, and in many cases gradually regresses without treatment with observation.[17]

Evaluation of the causes is especially important if gynecomastia arose before puberty, is rapidly increasing, is accompanied by pronounced systemic symptoms, or there are indications of medications and substances that can affect hormonal levels. [18]

The tactics are usually stepwise: first, observation and elimination of possible provoking factors, and in case of persistent severe pain or long-term persistence, treatment options are discussed with a specialist, including drug and surgical approaches in individual cases. [19]

Table 4. Approach to the assessment of gynecomastia in an adolescent

Situation	What to do first	What usually happens next?
Typical pubertal picture	Examination, Tanner stage, dynamics	Observation
Rapid enlargement or tight knot	Examination plus visualization as indicated	Additional tests and consultations
Pre-pubertal or systemic symptoms	Extended assessment of causes	Endocrinological examination

[20]

Infections: Mastitis and abscesses in newborns and infants

Mastitis in newborns and infants is most often associated with bacterial penetration through the skin, with manipulation, including massage and attempts at squeezing, being a significant risk factor in many descriptions. [21]

Clinically, local hyperemia, warmth, pain, increased compaction and possible systemic signs are alarming, and fluctuation may appear when an abscess forms. [22]

Ultrasound examination helps to differentiate inflammatory infiltrate from abscess and plan treatment, especially if symptoms increase or there is doubt about the diagnosis. [23]

Treatment should be started early, usually includes antibiotic therapy, and an abscess may require drainage, so it is safer to proceed through a pediatrician and pediatric surgeon rather than through home methods.[24]

Table 5. Inflammation of the mammary gland in an infant: practical steps

Step	The essence	For what
1	Assess the general condition and temperature	Detect systemic infection
2	Skin examination and palpation	Distinguish physiology from inflammation
3	Ultrasound examination if suspected	Check for an abscess
4	Treatment as prescribed by a doctor	Reduce the risk of complications

[25]

Nipple lumps and discharge in children: what happens most often

In children and adolescents, breast masses are rare and mostly benign, and ultrasound is usually considered the first line of imaging.[26]

The most common benign solid lesion in adolescents is fibroadenoma, and with a typical picture, observation with size control is often chosen if there are no signs of rapid growth or atypia. [27]

Biopsy is more often considered in cases of rapidly growing lesions, large size, atypical ultrasound features, or questionable clinical features, as it allows the exclusion of rare but important diagnoses. [28]

Nipple discharge in young children, including bloody discharge, is in most reports associated with benign causes such as dilated ducts and often resolves on its own but requires examination and usually ultrasound to be safe.[29]

Table 6. Red flags that require urgent assessment

Sign	Why is it important?	What do they usually do?
Rapid node growth	Risk of rare tumors and complications	Ultrasound examination and decision on biopsy
Skin changes, retraction	May indicate a more serious process.	Urgent consultation
Enlarged lymph nodes	Inflammation or rare oncopathology	Root cause assessment and visualization
Bloody discharge persists	The ducts need to be checked	Examination plus ultrasound
Fever with redness	Mastitis and abscess are possible	Urgent treatment

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Practical examination algorithm: what to ask and what to prescribe according to indications

The basis of diagnosis is anamnesis and examination: age of onset of changes, rate of progression, pain, trauma, medications, as well as an assessment of growth dynamics and staging of sexual development according to Tanner. [31]

When precocious puberty is suspected, an assessment of growth rate, bone age, and hormonal tests as prescribed by an endocrinologist are usually important, since it is the dynamics that helps to distinguish a benign variant from a progressive process. [32]

In the case of gynecomastia in adolescents, the scope of tests depends on the clinical picture: in the case of a typical course, observation is often sufficient, while in the case of atypical signs, a search for endocrine, medicinal and tumor causes is considered. [33]

For nodules and discharges, imaging usually begins with ultrasound, and further steps are selected based on the results and clinical presentation to minimize unnecessary interventions while not missing rare, dangerous conditions.[34]

Table 7. Examinations and typical indications

Examination	When it is needed more often	What does it give?
Ultrasound examination	Node, discharge, suspected abscess	Distinguishes cysts from solid formations, helps with abscesses
Hormonal tests	Progressive early development or atypical gynecomastia	Helps to find endocrine causes
Bone age assessment	Suspected precocious puberty	Reflects the "acceleration" of ripening
Biopsy as indicated	Rapid growth, atypia on ultrasound examination	Clarifies the diagnosis

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