Nipple discharge cytology

A spontaneous nipple discharge not related to lactation or pregnancy is an abnormal finding. It may result from a lesion in the breast (such as papilloma or carcinoma) or from a hormonal abnormality (such as a prolactin-secreting pituitary adenoma).

Cytologic examination of a nipple discharge is usually helpful when no palpable or mammographic abnormality is identified; otherwise, a fine needle aspiration (FNA) or excisional biopsy is usually performed.

The sensitivity for malignancy of nipple discharge cytology ranges from 40 to 60%. It can not be used as a screening test for breast cancer because a discharge can be obtained only in few asymptomatic women.

The breast is gently massaged in the direction of the nipple and a glass slide is touched to the secreted drops. It is not usually necessary to smear the discharge unless it is abundant. The slides are fixed by spray fixation or by immersion in 95% ethyl alcohol and stained with a Romanowsky-type stain.

Evaluation of nipple secretions

A nipple discharge may be unilateral or bilateral; unilateral ones are more likely to be malignant. The secretion can be milky, serous, purulent or bloody. Cancer is most likely  when the discharge is macroscopically bloody.

Benign nipple secretions - cytological diagnostic features

• Usually sparsely cellular
• Ductal cells
• Foamy cells
• Inflammatory cells
• Red blood cells

Benign ductal cells are molded around one another and arranged in tight clusters, which can be small and spherical or large and branching; isolated cells are very uncommon. The cells are usually small, with scanty cytoplasm, but sometimes larger with abundant cytoplasm. Foamy cells are histiocytes with abundant vacuolated cytoplasm and round or oval nuclei. When the secretion contains several groups of benign ductal cells, especially in large, branching clusters, an intraductal papilloma or a florid intraductal hyperplasia are likely to be present. These lesions can only be distinguished histologically.

Malignant nipple secretions - cytological diagnostic features

• Clusters and single enlarged ductal cells
• Nuclear pleomorphism
• Stripped nuclei
• Nucleoli
• Inflammatory cells
• Red blood cells
• Necrotic debris