The diagnostic accuracy of ultrasound, mammography, and aspiration biopsy ranges from about 70% to 80%, and varies with the training and skills of the clinician or technician. Therefore, a high degree of suspicion for cancer and excellent patient follow-up should be sustained for a breast lump or nipple discharge.
Ultrasound is helpful in differentiating solid from cystic lesions. In women under age 30 years, ultrasound is often the first step in the evaluation of a cyst or a mass. The ultrasound finding of a cystic lesion can be followed by aspiration of the cyst, eliminating it to make sure it is not concealing another abnormal breast finding. The ultrasound identification of a solid mass can be followed by tissue biopsy.
In the presence of a palpable mass or nipple discharge, a diagnostic mammogram is necessary to identify palpable lumps or abnormal screening mammograms. It consists of additional views to clarify the features and location of palpable masses. Additional views could include spot compression, magnification, exaggerated craniocaudal (CC) to the medial or lateral side, tangential, and 90-degree lateral views. Mammography is of less diagnostic value in women younger than age 30 because of the density of the breast tissue.
Magnetic Resonance Imaging
Magnetic resonance imaging (MRI) is used primarily to evaluate abnormal areas that are seen on a mammogram, and to assess breast implants for leaks or ruptures. MRI is sometimes useful in viewing breast abnormalities that can be felt, but are not visible with mammography or ultrasound. It also can be used to image dense breast tissue, which is often found in younger women. Contrast is used to enhance the vascularity of malignant lesions. Although MRI is highly sensitive (85% to 100%), it lacks specificity. MRI is inferior to mammography in detecting in situ cancers and cancers smaller than 3 mm. The role of MRI in the evaluation of nipple discharge is evolving.
Fine Needle Aspiration and Cytological Examination
Fine needle aspiration (FNA) biopsy uses a smallgauge needle to obtain fluid and cellular material. FNA is a routinely performed office procedure that is both diagnostic and therapeutic. It immediately determines if the lump is a cyst or a solid tumor. The aspirate is sent for cytological evaluation to determine the presence or absence of malignant cells. If cytology findings of the aspirate are negative, the mass completely goes away, and is not present on follow-up examinations, no further treatment is necessary.
Stereotactic or Needle Localization Biopsy
Fine needle aspiration can also be used with ultrasonography or stereotactic imaging to further assess and obtain adequate sampling in poorly defined palpable masses. The lesion is located, marked, and verified by imaging to assist in the identification of the tissue to be sampled.
Core Needle Biopsy
Core needle biopsy (CNB) uses a large-gauge needle to obtain several cores of tissue. It produces a larger tissue
sample than FNA. It can be used in conjunction with ultrasonography or stereotactic imaging for small or difficult to palpate lesions. Local anesthesia is required.
Excisional biopsy is the gold standard for evaluating breast masses. It is performed in an operating room using local or general anesthetic and the entire lesion is removed. Excisional biopsy is indicated if there is a large breast mass or for those lesions in which more conservative biopsy has produced equivocal results. The surgical specimen is evaluated histologically.
Microscopy of nipple discharge can reveal fat cells of galactorrhea, leukocytes of infection, or red blood cells. Care must be taken to prevent the slide from drying out. Place a coverslip on the slide immediately after obtaining the specimen and review the slide shortly after it is prepared.
A cytological specimen of discharge is placed directly from the nipple onto the slide, or if there is only a small amount of discharge, it can easily be collected with a saline-saturated cotton-tipped applicator and spread onto the slide. The slide is then fixed in the same manner as a cervical specimen. This technique can expose cancerous cells. However, a smear with negative findings is not conclusive and additional workup is mandated.
A ductogram is useful in evaluating the cause of nipple discharge. Contrast medium is injected into the discharging duct, followed by a mammogram. The mammogram may show a filling defect (commonly an intraductal papilloma), a dilated or cystic appearance (duct ectasia or fibrocystic disease), or an abrupt obstruction (malignancy).
Serum Prolactin Level
Elevated serum prolactin levels can produce nipple discharge. Hyperprolactinemia should be suspected when the prolactin level exceeds 20 to 25 ng/mL. Prolactin elevation, secondary to medications, is generally less than 100 ng/mL. Prolactinomas are found when the prolactin level exceeds 150 ng/mL.
Thyroid Function Testing
Thyroid-stimulating hormone (TSH) is high in hypothyroidism. About 20% of patients with hyperprolactinemia have hypothyroidism. TSH testing is done torule out primary hypothyroidism as a cause of the hyperprolactinemia and associated nipple discharge.