Mastitis and breast abscess
How milk stasis inflames the breastfeeding breast and Staphylococcus aureus turns it into infection or abscess, how smoking and squamous metaplasia cause periductal mastitis, and how duct ectasia, granulomatous mastitis and fat necrosis mimic cancer.
By the end, you can
- Describe the lobes, lactiferous ducts and nipple of the breast, and how milk is made and let down.
- Explain how milk stasis causes inflammatory mastitis and how Staphylococcus aureus entering a cracked nipple causes infection and abscess.
- Explain how smoking and squamous metaplasia of the lactiferous ducts lead to periductal mastitis, subareolar abscess and mammary duct fistula.
- Compare duct ectasia, idiopathic granulomatous mastitis and fat necrosis, and explain why each can mimic carcinoma.
- Distinguish infective mastitis from inflammatory breast cancer, recognise the classic tissue changes and tests, and explain how the main treatments act on each mechanism.
What it is
Mastitis is inflammation of the breast, with or without infection; a breast abscess is a walled-off collection of pus within it. Lactational mastitis arises from milk stasis in the breastfeeding breast, often complicated by Staphylococcus aureus. Non-lactational forms include periductal mastitis, duct ectasia and idiopathic granulomatous mastitis. Fat necrosis is an inflammatory reaction to injured fat that mimics cancer.
5 types to tell apart
- Lactational (puerperal) mastitis and abscess
- Milk stasis and inflammation in a segment of the breastfeeding breast, often infected by Staphylococcus aureus through a cracked nipple; an abscess can follow.
- Periductal mastitis
- Inflammation round the subareolar ducts, strongly linked with smoking, caused by squamous metaplasia and keratin plugging; recurrent subareolar abscesses and mammary duct fistula.
- Duct ectasia
- Dilated large ducts with thick secretions and chronic periductal inflammation, mainly in women around and after the menopause; discharge and nipple retraction.
- Idiopathic granulomatous mastitis
- Granulomas centred on the lobules in young women after pregnancy, with abscesses and sinuses; a diagnosis made only after infection is excluded.
- Fat necrosis
- Death of breast fat after injury, surgery or radiotherapy, healing with foamy macrophages, oil cysts, fibrosis and calcification.
Normal function
The breast: lobes, ducts and the let-down of milk
Beneath the , the breast is mostly , with 15 to 20 of glandular tissue arranged like the spokes of a wheel and held by fibrous . Each lobe drains through its own , which widens into a under the and opens on the . Where the duct opens, its last millimetre or two is lined by keratinising squamous epithelium like the skin; deeper, it is lined by two layers of duct cells.
In pregnancy the ducts branch and clusters of alveoli bud from them. After birth, each feed releases a spike of prolactin, which drives the lining cells (lactocytes) to make milk for the next feed. Suckling also triggers oxytocin from the posterior pituitary, which contracts the myoepithelial cells round the alveoli and squeezes milk into the ducts: the let-down. Regular removal of milk keeps supply matched to demand.
Between the lactocytes, tight junctions close after birth so that milk stays in the alveoli and does not leak into the surrounding tissue. The skin of the nipple and areola, protected by the oily secretion of the areolar glands, carries skin bacteria, including Staphylococcus aureus, as does the baby’s mouth.
Underlying change · Step 1 of 6
Lactational mastitis: milk stasis and inflammation
The full lesson is part of Student Pro
It takes you through all 6 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 10 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 2 of 6
Infection and abscess: Staphylococcus aureus enters through the nipple
The full lesson is part of Student Pro
It takes you through all 6 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 10 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 6
Periductal mastitis: smoking, keratin and the subareolar abscess
The full lesson is part of Student Pro
It takes you through all 6 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 10 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 6
Duct ectasia and idiopathic granulomatous mastitis
The full lesson is part of Student Pro
It takes you through all 6 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 10 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 6
Fat necrosis: injured fat that mimics cancer
The full lesson is part of Student Pro
It takes you through all 6 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 10 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 6 of 6
The red breast that is cancer: inflammatory breast carcinoma
The full lesson is part of Student Pro
It takes you through all 6 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 10 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 6 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 10 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 .
Exam detail
Exam detail
The full lesson is part of Student Pro
It takes you through all 6 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 10 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 .
Treatment
How treatment works
The full lesson is part of Student Pro
It takes you through all 6 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 10 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 6 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 10 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 6 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 10 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 .