What labs are recommended for evaluating abnormal discharge from the breast?

Laboratory Testing for Abnormal Breast Discharge

Laboratory testing is generally not recommended for evaluating abnormal breast discharge; the diagnostic workup relies primarily on clinical assessment and imaging studies rather than laboratory tests. 1

Clinical Characterization Takes Priority Over Labs

The evaluation of abnormal breast discharge begins with determining whether the discharge is physiologic or pathologic based on specific clinical characteristics, not laboratory analysis 1, 2:

Physiologic Discharge Characteristics:

• Bilateral presentation 1, 2
• Multiple duct involvement 1, 2
• Non-spontaneous (requires manipulation/compression) 2
• White, green, yellow, or clear color 1, 2

Pathologic Discharge Characteristics:

• Spontaneous occurrence 1, 3
• Unilateral presentation 1, 3
• Single duct involvement 1, 3
• Bloody, serous, or serosanguineous appearance 1, 3

Why Labs Are Not Part of Standard Evaluation

The standard evaluation of all patients with pathologic nipple discharge includes history, physical examination, and imaging evaluation—not laboratory testing. 1 The ACR Appropriateness Criteria, which represent the most authoritative guidelines on this topic, make no mention of laboratory tests as part of the diagnostic algorithm 1.

Specific Exception: Galactorrhea

The only scenario where laboratory testing becomes relevant is when evaluating galactorrhea (milky discharge), which may indicate:

• Pregnancy-related causes 4
• Drug-induced hyperprolactinemia 4
• Hypothyroidism or hyperthyroidism 4
• Pituitary adenoma 5, 4

In these cases, consider:

• Serum prolactin level 4
• Thyroid function tests (TSH, free T4) 4
• Pregnancy test (β-hCG) 4

The Evidence-Based Diagnostic Algorithm

For pathologic discharge, proceed directly to imaging rather than laboratory testing 1, 3:

1. Diagnostic mammography as the initial imaging modality 1, 3
2. Breast ultrasound as a complementary examination, particularly valuable for retroareolar region evaluation 1, 3
3. MRI or ductography if initial imaging is negative but pathologic discharge persists 1
4. Image-guided core biopsy if imaging identifies a suspicious lesion 1, 3

Critical Risk Stratification (Without Labs)

The risk of malignancy in pathologic nipple discharge ranges from 5-21% and increases with 1, 3:

• Age >40 years (3% if ≤40 years, 10% if 40-60 years, 32% if >60 years) 1
• Presence of palpable mass (61.5% malignancy rate vs 6.1% without mass) 1
• Male sex (23-57% malignancy rate) 1

Common Pitfall to Avoid

Do not delay imaging workup while waiting for laboratory results. The sensitivity of mammography for detecting malignancy in pathologic discharge ranges from 15-68%, and ultrasound has a sensitivity of 26% 1, making imaging—not laboratory testing—the cornerstone of evaluation. Negative imaging does not reliably exclude neoplasia, with up to 20% of lesions located >3 cm beyond the nipple potentially missed 1, 6.