[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Breast](https://durgical.com/en/general-pathology/areas/breast/) › Inflammatory breast lesions

# Inflammatory breast lesions

- Lesion

Breast inflammation ranges from the infection of breastfeeding to lesions that feel and look like cancer, which is why many end up biopsied.

Updated Nov 12, 2026

## Key points

- Acute mastitis: lactation, cracked nipple, Staphylococcus aureus (abscess) or streptococci (spreading); painful, red, warm breast with fever.
- Squamous metaplasia of lactiferous ducts (periductal mastitis, Zuska disease): smokers; keratin plugs, duct rupture, subareolar abscess and fistula to the areolar edge; recurs unless the duct is excised.
- Duct ectasia: older parous women; dilated ducts with thick secretions, periductal chronic inflammation rich in plasma cells; nipple retraction mimics cancer.
- Fat necrosis: after trauma, surgery or radiation; firm mass, calcifications and skin retraction that mimic cancer.
- Lymphocytic mastopathy: hard masses in women with type 1 diabetes or autoimmune thyroid disease.
- Granulomatous mastitis: systemic disease (granulomatosis with polyangiitis, sarcoidosis), infections (tuberculosis, fungi, Corynebacterium), foreign material, or idiopathic lobular disease.

## What it is

Inflammatory breast disorders are uncommon outside lactation, and several of them mimic carcinoma by forming hard masses, retracting the skin or calcifying. Acute mastitis is a bacterial infection of the lactating breast. Squamous metaplasia of lactiferous ducts, strongly tied to smoking, plugs the ducts with keratin and causes recurrent subareolar abscesses. Duct ectasia, fat necrosis, lymphocytic mastopathy and granulomatous mastitis complete the group.

## Structure

- Acute mastitis: neutrophils filling ducts and lobules, sometimes with abscess cavities.
- Squamous metaplasia: keratinizing squamous epithelium extending deep into nipple ducts, keratin debris, and a granulomatous reaction to spilled keratin.
- Duct ectasia: dilated ducts with inspissated secretions and foamy macrophages, surrounded by plasma cells, lymphocytes and fibrosis.
- Fat necrosis: necrotic fat cells, foamy macrophages, multinucleated giant cells, haemosiderin, then fibrosis and calcification.
- Lymphocytic mastopathy: dense keloid-like collagen with lymphocytes around ducts, lobules and vessels.
- Cystic neutrophilic granulomatous mastitis: granulomas around clear vacuoles that contain gram-positive rods (Corynebacterium).

## Step by step

- During lactation, a cracked nipple lets skin bacteria into the milk ducts, where stasis helps them grow.
- In smokers, the duct lining undergoes squamous metaplasia; keratin plugs block the duct.
- Blocked ducts dilate and rupture; their contents escape into the stroma.
- Keratin, lipid or milk products provoke intense inflammation, granulomas and abscesses.
- Healing leaves fibrosis that retracts the nipple or skin and can feel like a tumour.

## Inflammatory breast lesions at a glance

| Lesion | Typical patient | Key histology | Why it matters |
| --- | --- | --- | --- |
| [Acute mastitis and abscess](https://durgical.com/en/conditions/acute-mastitis/) | Breastfeeding woman | Neutrophils, abscess | Needs antibiotics or drainage |
| [Squamous metaplasia of lactiferous ducts](https://durgical.com/en/conditions/breast-abscess/) | Smoker | Keratinizing metaplasia, keratin granulomas | Recurrent subareolar abscess and fistula |
| Duct ectasia | Older parous woman | Dilated ducts, plasma cells | Mimics cancer (retraction, mass) |
| Fat necrosis | After trauma or surgery | Foamy macrophages, giant cells, calcification | Mimics cancer on imaging |
| [Lymphocytic mastopathy](https://durgical.com/en/conditions/type-1-diabetes-mellitus/) | Type 1 diabetes, autoimmune thyroid disease | Keloid-like stroma, lymphocytes | Hard mass, often recurrent |
| [Granulomatous mastitis](https://durgical.com/en/conditions/tuberculosis/) | Parous women; systemic disease | Granulomas, sometimes microbes | Exclude tuberculosis and fungi |

## Clinical notes

- Lactational mastitis is treated with continued milk drainage and antibiotics; breastfeeding usually continues.
- Inflammatory carcinoma can look like mastitis: a red, swollen breast outside lactation that does not respond to antibiotics needs a biopsy.
- In Colombia, tuberculous mastitis should be considered in a granulomatous breast lesion.

## Memory aid

Milk, smoke, age and trauma: the four doors to breast inflammation (mastitis, Zuska, ectasia, fat necrosis).

## Test yourself

Think of the answer, then tap the question to see it.

## Which organism most often causes lactational breast abscess?

Staphylococcus aureus.

## What is the strongest risk factor for squamous metaplasia of lactiferous ducts?

Smoking.

## Why is fat necrosis clinically important?

It forms a firm mass with calcifications and skin retraction that mimics carcinoma on examination and imaging.

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## Elsewhere in DurgiPedia

- [Lactation](https://durgical.com/en/physiology/lactation/)
- [Breast: ducts, lobules and changes with life stage](https://durgical.com/en/histology/breast-ducts-lobules-and-changes-with-life-stage/)

## Connections

## Related 7

- [Breast disease: presentations and developmental anomalies](https://durgical.com/en/general-pathology/breast-disease-presentations-and-developmental-anomalies/)
- [Invasive breast carcinoma of no special type](https://durgical.com/en/general-pathology/invasive-breast-carcinoma-of-no-special-type/)
- [Patterns of acute inflammation: serous, fibrinous, purulent, abscess, ulcer](https://durgical.com/en/general-pathology/patterns-of-acute-inflammation-serous-fibrinous-purulent-abscess-ulcer/)
- [Patterns of necrosis: coagulative, liquefactive, caseous, fat, fibrinoid, gangrenous](https://durgical.com/en/general-pathology/patterns-of-necrosis-coagulative-liquefactive-caseous-fat-fibrinoid-gangrenous/)
- [Granulomatous inflammation: caseating vs non-caseating, the causes to know](https://durgical.com/en/general-pathology/granulomatous-inflammation-caseating-vs-non-caseating-the-causes-to-know/)
- [Metaplasia](https://durgical.com/en/general-pathology/metaplasia/)
- [Tobacco: how smoking injures tissue](https://durgical.com/en/general-pathology/tobacco-how-smoking-injures-tissue/)

## Related conditions 6

- [Acute mastitis](https://durgical.com/en/conditions/acute-mastitis/)
- [Breast abscess](https://durgical.com/en/conditions/breast-abscess/)
- [Type 1 diabetes mellitus](https://durgical.com/en/conditions/type-1-diabetes-mellitus/)
- [Tuberculosis](https://durgical.com/en/conditions/tuberculosis/)
- [Sarcoidosis](https://durgical.com/en/conditions/sarcoidosis/)
- [Granulomatosis with polyangiitis](https://durgical.com/en/conditions/granulomatosis-with-polyangiitis/)

## Microorganisms 2

- [Staphylococcus aureus](https://durgical.com/en/microbiology/staphylococcus-aureus/)
- [Mycobacterium tuberculosis](https://durgical.com/en/microbiology/mycobacterium-tuberculosis/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Acute Mastitis](https://www.ncbi.nlm.nih.gov/books/NBK557782/) (StatPearls (NCBI Bookshelf), 2026); [Breast Abscess](https://www.ncbi.nlm.nih.gov/books/NBK459122/) (StatPearls (NCBI Bookshelf), 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/inflammatory-breast-lesions/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/inflammatory-breast-lesions/