Fibrocystic breast disease. Benign tumors: epithelial and mixed
Breast lumps: only 10% of all patients coming in with breast lumps have cancer, 40% meanwhile are fibrocystic changes, with another 20% being benign neoplasia (misc benign and fibroadenoma), 30% are no lumps at all.
First, histology reminder, breasts are made of lobules (milk producing glands) and ducts (that carry the milk to the nipple). These are surrounded by glandular, fibrous and fatty tissues.
The term fibrocystic breast disease designates the pathological process of cyst formation and fibrosis, they are likely a result of breast changes that occur in the normal menstrual cycle. They can be subdivided as below:
- Nonproliferative changes
- Cysts and fibrosis - the most common type of fibrocystic lesions, there is an increase in fibrous stroma along with dilation of ducts and formation of cysts
- Secretions in the cysts can calcify, producing microcalcifications on mammograms.
- Frequently the fibrotic cysts have large polygonal cells lining them, in a setting known as apocrine metaplasia
- Proliferative changes
- Epithelial hyperplasia - increased epithelial cells in the lumen of the ducts and lobules of the breast.
- Fenestrations and ductal papillomatosis can be observed
Features of fibrocystic changes can help us determine if there is an increased risk of cancer:
- Minimal/no increase in risk where there is fibrosis, cystic changes, apocrine metaplasia
- Slightly increased risk where there is moderate hyperplasia or ductal papillomatosis
- There is significantly increased risk where there is atypical hyperplasia
The most common benign breast tumour is a fibroadenoma, it can develop in puberty and is a mixture of stromal and epithelial tissues, they develop from the lobules (milk producing glands) and form a solid fibrous lump.
H&E, fibroadenoma: proliferating intralobular stroma presses on the ducts and squeezes them into slit-like, curved spaces lined by epithelium.
Image: “Fibroadenoma 10X” by Department of Pathology, Calicut Medical College, CC BY-SA 4.0, via Wikimedia Commons.
Examples: two other benign tumours named in the title:
- Intraductal papilloma (epithelial): a small papillary tumour in a large duct under the nipple; classic sign is bloody nipple discharge
- Phyllodes tumour (mixed, fibroepithelial): like a fibroadenoma but with more cellular stroma forming leaf-like projections; larger, in older women (40s-60s), can recur and a few are malignant