Hyperplastic and benign breast changes
How the terminal duct lobular unit responds to cyclical hormones, why cysts, hyperplasia with and without atypia, fibroadenoma and phyllodes tumour form, and what each means for later breast cancer risk.
By the end, you can
- Describe the terminal duct lobular unit, its luminal and myoepithelial cells, and how hormones change it through the cycle and life.
- Explain how cyclical stimulation leads to fibrocystic change, and why it adds little or no cancer risk.
- Distinguish proliferative changes without atypia from atypical ductal and lobular hyperplasia, and relate each to the risk of breast cancer.
- Compare fibroadenoma and phyllodes tumour in origin, appearance and behaviour.
- Relate the common findings (lumps, cyclical pain, nipple discharge, calcification) to the lesion that causes them.
What it is
Benign breast changes are non-cancerous alterations of the breast glands and their stroma. Pathologists sort the epithelial changes into three groups by the cancer risk they carry: non-proliferative (fibrocystic change), proliferative without atypia (usual ductal hyperplasia, sclerosing adenosis, papilloma, radial scar) and atypical hyperplasia (ductal or lobular). The fibroepithelial tumours, fibroadenoma and phyllodes tumour, arise from the stroma of the lobule.
6 types to tell apart
- Non-proliferative (fibrocystic) change
- Cysts, fibrosis and apocrine metaplasia; very common in the reproductive years and regarded as an exaggeration of normal cyclical change. It adds little or no cancer risk.
- Proliferative change without atypia
- More epithelial cells of a mixed, normal kind: usual ductal hyperplasia, sclerosing adenosis, intraductal papilloma and radial scar. A small rise in risk, in both breasts.
- Atypical hyperplasia
- A small, clonal population of uniform cells: atypical ductal hyperplasia (ADH) resembles low-grade ductal carcinoma in situ; atypical lobular hyperplasia (ALH) resembles lobular carcinoma in situ. A moderate rise in risk.
- Fibroepithelial tumours
- Fibroadenoma, the commonest benign breast tumour in young women, and the rarer phyllodes tumour (benign, borderline or malignant), in which the stroma grows into leaf-like fronds.
- Inflammatory and reactive mimics
- Fat necrosis after injury, duct ectasia (dilated large ducts with thick secretions and inflammation) and mastitis can all form a firm lump or draw in the skin or nipple, mimicking a carcinoma.
- Gynaecomastia
- Benign enlargement of the male breast ducts and stroma when the balance of oestrogen to androgen rises (puberty, older age, liver disease, some drugs); a rubbery disc under the nipple.
US spelling: tumours → tumors, tumour → tumor, oestrogen → estrogen.
Normal function
The terminal duct lobular unit
The breast is a modified sweat gland of 15 to 20 , set in fat and fibrous tissue. Each lobe drains through its own to the . Inside a lobe the ducts branch and end in terminal duct lobular units (TDLUs): a terminal duct and the cluster of small acini (ductules) of a lobule, surrounded by loose, hormone-responsive intralobular stroma. Denser fibrous stroma and fat lie between the lobules.
Two layers of cells line every duct and acinus. Inner luminal cells secrete milk, and some of them carry receptors for oestrogen and progesterone. Outer myoepithelial cells sit on the basement membrane and contract to squeeze milk out. Pathologists rely on this second layer: benign and in situ lesions keep it, invasive carcinoma loses it.
Hormones remodel the unit. Oestrogen lengthens and branches the ducts; progesterone adds acini. In each cycle the epithelium proliferates and the stroma swells after ovulation, then regresses, which is why breasts feel fuller before a period. Pregnancy brings full lobular development; after the menopause the lobules shrink and fat replaces them. Almost every benign and malignant breast lesion arises in the TDLU.
| Feature | Luminal cell | Myoepithelial cell |
|---|---|---|
| Position | Lines the lumen | Outer layer, on the basement membrane |
| Role | Secretes milk | Contracts to expel milk (oxytocin) |
| Hormone receptors | Some cells carry oestrogen and progesterone receptors | Usually none |
| Typical stains | Luminal keratins, E-cadherin | p63, smooth muscle myosin, basal keratins |
| In disease | Gives rise to hyperplasia, in situ and invasive carcinoma | Kept in benign and in situ lesions; absent around invasive carcinoma |
Simplified. The stroma of the lobule is a third component: it gives rise to fibroadenoma and phyllodes tumour.
Underlying change · Step 1 of 5
Fibrocystic change: cysts, fibrosis and apocrine metaplasia
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Underlying change · Step 2 of 5
Proliferative change without atypia
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 3 of 5
Atypical hyperplasia: a clone emerges
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Disrupted function · Step 4 of 5
Fibroadenoma and phyllodes tumour
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Consequences · Step 5 of 5
Lumps, pain, discharge and imaging
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Symptoms and signs
Symptoms, signs and findings
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Recap
Recap
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .
Self-check
Check your understanding
The full lesson is part of Student Pro
It takes you through all 5 steps of the mechanism, explains the symptoms, signs and findings each step causes, adds the exam detail and how treatment works where the lesson has them, then recaps it and lets you check yourself with 8 self-check questions. The full pathophysiology library: guided lessons with self-check questions comes with Student Pro, with 100 tutor answers a month and the full available catalogue.
Free to read: the introduction and .