Benign Breast Disorders

Benign breast disorders are diverse conditions that can be understood by appreciating the anatomy of the breast, which is mainly composed of epithelial and stromal aspects. The epithelial components includes the breast lobules, responsible for milk production, and lactiferous ducts, which channel milk to the nipple. The stromal component comprises fatty & fibrous connective tissue, making up most of the breast's volume when not lactating.

Mastitis is an inflammatory disorder affecting the breast ducts and is commonly associated with breastfeeding. It manifests as erythema and breast pain, most often initiated by nipple trauma during breastfeeding. A possible complication is the formation of a galactocele, a milk-filled cyst that can become infected, commonly by Staphylococcus aureus. Continued breastfeeding is recommended to alleviate ductal obstruction.

Mammary duct ectasia results from blocked lactiferous ducts laden with cellular debris. Clinical signs include breast pain and dilated ducts, along with a characteristic thick, greenish nipple discharge. Radiographic findings may show radio-opacities due to calcified secretions within the ducts.

Fat necrosis is typically caused by breast trauma, and presents as an irregular mass and breast pain. Like mammary duct ectasia, fat necrosis can also exhibit radiological opacities, often making it a differential diagnosis for breast cancer.

The most prevalent benign breast disorder in premenopausal women is fibrocystic change, which can be nonproliferative or proliferative.

Nonproliferative lesions include breast cysts, characterized by small, fluid-filled sacs scattered throughout the breast. Breast cysts are the most prevalent nonproliferative lesion, often manifesting as a lumpy breast texture due to fibrous stromal proliferation. Radiographically, these cysts may display regions of calcification, and manifest as ‘blue dome cysts’ on gross pathology.

Papillary apocrine change manifests as ductal epithelial cells that resemble apocrine glands. These cells are granular and can be associated with cyclic mastalgia in premenopausal women, particularly within the scope of non-proliferative fibrocystic change.

Proliferative lesions include epithelial hyperplasia, which features an increase in organized epithelial cells, leading to occlusion of the mammary ducts or lobules. When these cells undergo atypical changes—marked by disorganized architecture and dark purple nuclei—the condition escalates to atypical epithelial hyperplasia, which increases the risk of breast cancer.

Sclerosing adenosis is another proliferative lesion characterized by an overgrowth of glandular tissue in the lobules and accompanying fibrous tissue, or ‘sclerosis.’ Sclerosing adenosis also increases the risk of developing breast cancer.

Benign breast tumors include fibroadenomas, which are estrogen-responsive tumors that worsen in high estrogen states (pregnancy, lactation, pre-ovulation) and predominantly appear in young women. Fibroadenomas present as palpable masses that are well-defined, rubbery, and mobile. Histology shows proliferation in both the fibrous stroma and adenomatous ducts. In contrast, phyllodes tumors typically arise in women in their 40s and may display malignant behavior despite their benign classification.

Intraductal papillomas occur within lactiferous ducts, and are the leading cause of bloody nipple discharge. These growths can sometimes harbor cellular atypia or ductal carcinoma in situ, thereby heightening the risk for malignancy.

Lastly, Galactorrhea presents as bilateral milky nipple discharge unrelated to breastfeeding. It may arise either through mechanical factors or be precipitated by specific conditions like prolactinomas. Medications that inhibit dopamine receptors, particularly D2 dopamine receptor antagonists such as certain antipsychotics, can also cause galactorrhea.