Laboratory Testing for Nipple Discharge in a 19-Year-Old
For a 19-year-old with nipple discharge, the primary laboratory test to obtain is a serum prolactin level if the discharge is bilateral, milky, or spontaneous, as this evaluates for hyperprolactinemia from medications, pituitary tumors, or endocrine disorders. 1
Initial Clinical Characterization
The first step is determining whether the discharge is physiologic or pathologic, as this fundamentally changes the evaluation pathway:
Physiologic discharge characteristics: 2, 3
- Bilateral presentation
- Multiple ducts involved
- White, green, yellow, or clear color
- Only occurs with manipulation/compression (non-spontaneous)
- No associated breast mass
Pathologic discharge characteristics: 2, 3
- Unilateral presentation
- Single duct involvement
- Bloody, serous, or serosanguineous appearance
- Spontaneous occurrence
- Any single pathologic feature warrants full evaluation
Laboratory Testing Algorithm
For Physiologic/Milky Discharge:
Serum prolactin level is the primary laboratory test indicated 1, particularly when:
- Discharge is bilateral and milky (galactorrhea) 4
- Patient has spontaneous milky discharge 4
- Evaluating for hyperprolactinemia from antipsychotic medications, pituitary tumors, or endocrine disorders 1
For Pathologic Discharge:
No routine laboratory tests are indicated initially - the evaluation focuses on imaging rather than laboratory studies 2, 3. The cancer risk in women under 40 with pathologic discharge is only 3%, and even lower at age 19 4.
Imaging Rather Than Labs
For this age group, breast ultrasound is the initial examination of choice (rated 9/9 by ACR) if pathologic features are present, not laboratory testing 4. Mammography is not recommended as an initial test in women under 30 years due to dense breast tissue limiting sensitivity and extremely low breast cancer risk 2.
Critical Pitfall to Avoid:
Do not order extensive laboratory panels for nipple discharge evaluation. The workup is primarily imaging-based for pathologic discharge and prolactin-based for physiologic/milky discharge 4, 1. Ordering tumor markers or other cancer screening labs is not indicated and provides no diagnostic value in this clinical scenario.
Management Based on Discharge Type
If physiologic discharge with normal prolactin and current screening (when age-appropriate): 2
- No further investigation needed
- Patient education to stop breast compression
- Instruct to report development of spontaneous discharge
- Proceed directly to breast ultrasound with focused retroareolar imaging
- Add mammography only if ultrasound shows suspicious findings or strong family history
- Consider thyroid function tests only if clinical signs of thyroid disease present alongside galactorrhea