A boy presents with a palpable lump at the nipple; what is the most likely diagnosis and how should it be evaluated and managed?

Breast Lump at Nipple in a Boy

The most likely diagnosis is physiologic pubertal gynecomastia, which affects approximately 50% of mid-pubertal boys and resolves spontaneously in over 90% of cases within 24 months. 1

Most Likely Diagnosis

Pubertal gynecomastia is the presumptive diagnosis in an adolescent boy presenting with a nipple lump, characterized by benign proliferation of glandular breast tissue beneath the areola. 1, 2 The condition results from a transient imbalance between estrogen and testosterone during puberty, typically resolving by age 18 when adult androgen/estrogen ratios are achieved. 2

Key Distinguishing Features by Age:

• Prepubertal boys (age <9 years): Gynecomastia is rare (only 5% of referrals) and warrants immediate evaluation for possible endocrine disorders, as 93% of prepubertal cases are idiopathic but require thorough workup to exclude pathology. 3, 4
• Pubertal boys: Common and usually physiologic, presenting as a soft, rubbery, or firm mobile mass directly under the nipple, often painful especially when present for less than 6 months. 5
• Bilateral in approximately 50% of patients. 5

Clinical Evaluation Algorithm

Step 1: Confirm True Gynecomastia vs. Pseudogynecomastia

• Palpate for glandular tissue directly beneath the nipple-areolar complex to distinguish true gynecomastia from pseudogynecomastia (fatty tissue deposition), especially in boys with elevated BMI. 5, 1

Step 2: Assess for Red Flags Requiring Immediate Workup

• Hard, fixed, or eccentric mass (suggests malignancy, though male breast cancer is extremely rare with median age 63 years). 5
• Unilateral mass with suspicious features (asymmetry, skin changes, nipple retraction). 5
• Prepubertal presentation (age <9 years requires endocrine evaluation). 4, 3
• Signs of undervirilization or systemic disease (testicular atrophy, signs of liver disease, Klinefelter syndrome features). 1

Step 3: Determine Need for Imaging

For typical pubertal gynecomastia with benign clinical features, no imaging is routinely recommended, as imaging leads to additional unnecessary benign biopsies without improving outcomes. 5

Imaging is indicated only if:

• Differentiation between benign disease and breast cancer cannot be made clinically. 5
• For boys under 25 years with indeterminate findings: Ultrasound is the initial imaging study of choice. 5
• If ultrasound shows suspicious features, proceed to mammography or digital breast tomosynthesis before considering biopsy. 5

Laboratory Evaluation

For prepubertal boys or those with atypical features, obtain:

• Testosterone, estradiol, SHBG, LH, FSH. 1, 2
• TSH, prolactin (if testosterone low with low/normal LH). 1
• hCG, AFP (to exclude testicular tumors). 1
• Liver and renal function tests. 1
• Karyotype if testes volumes <6 mL in pubertal patients (to exclude Klinefelter syndrome, which has a 24.7-fold increased risk of gynecomastia). 2, 6

Testicular ultrasound is recommended as palpation has low sensitivity for detecting testicular tumors. 1

Management Approach

For Physiologic Pubertal Gynecomastia:

Watchful waiting with sympathetic reassurance is the mainstay of treatment, given the benign nature and high spontaneous resolution rate (>90% within 24 months). 1, 4, 2

Indications for Intervention:

• Persistence beyond 12 months (tissue becomes fibrotic and less responsive to medical therapy). 6
• Completion or near-completion of puberty without resolution. 2
• Significant psychosocial distress. 7

Medical Therapy:

• Not recommended in general for idiopathic pubertal gynecomastia, as there are insufficient data supporting efficacy in children. 1, 4
• Selective estrogen receptor modulators (SERMs) and aromatase inhibitors are not justified in routine cases. 1

Surgical Treatment:

Surgical removal of breast glandular tissue is the therapy of choice for boys with persistent gynecomastia who have completed or nearly completed puberty, especially if causing significant psychological distress. 1, 2, 7

Common Pitfalls to Avoid

• Failing to distinguish true gynecomastia from pseudogynecomastia in obese patients, which requires palpation for glandular tissue. 5, 6
• Ordering unnecessary imaging in clear cases of physiologic pubertal gynecomastia, which increases false-positive biopsies without benefit. 5
• Missing prepubertal gynecomastia, which requires immediate endocrine evaluation unlike the pubertal variant. 4, 3
• Not performing testicular examination and ultrasound, as palpation alone has low sensitivity for detecting tumors that may cause gynecomastia. 1