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Inflammatory dis order of breast

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The image shows a chapter from what appears to be Robbins Pathology (with KD Tripathi also open), specifically the table of contents for the breast chapter. The "Inflammatory Disorders" section lists: Acute Mastitis, Squamous Metaplasia of Lactiferous Ducts, Duct Ectasia, Fat Necrosis, Lymphocytic Mastopathy, and Granulomatous Mastitis - all at page 946-947.
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Inflammatory Disorders of the Breast

(From Robbins, Cotran & Kumar - Pathologic Basis of Disease, Chapter 23, p. 946-947)
Inflammatory diseases of the breast are rare - accounting for less than 1% of breast symptoms. They are caused by infections, autoimmune disease, or foreign body-type reactions to extravasated keratin or secretions. Inflammatory breast cancer clinically mimics inflammation and must always be excluded in a female presenting with an erythematous swollen breast.

1. Acute Mastitis

Etiology & Setting: Occurs almost exclusively during the first month of breastfeeding (lactational mastitis). Cracks and fissures in the nipple act as the portal of entry for:
  • Staphylococcus aureus (most common) - leads to localized single/multiple abscesses
  • Streptococci (less common) - causes spreading cellulitis
Clinical features: Breast erythema, pain, tenderness, and fever. Initially one duct system/sector is involved; if untreated, the infection can spread to the entire breast.
Treatment: Appropriate antibiotics + continued expression of milk. Surgical drainage is only rarely required.

2. Squamous Metaplasia of Lactiferous Ducts

(also called: Recurrent subareolar abscess / Periductal mastitis / Zuska disease)
Pathogenesis: Keratinizing squamous metaplasia extends deep into the nipple duct past the normal squamocolumnar junction. Shed keratin is trapped, plugging the duct → dilation → rupture → intense chronic granulomatous inflammatory response to keratin spilling into periductal tissue.
Key association: >90% of affected individuals are smokers. Tobacco-associated relative vitamin A deficiency alters ductal epithelial differentiation.
Clinical features:
  • Painful erythematous subareolar mass mimicking a bacterial abscess
  • Recurrent fistula tract that burrows under the nipple smooth muscle and opens at the edge of the areola
  • Nipple inversion due to traction from scarring
Treatment: En bloc surgical removal of the involved duct and fistula tract (simple incision and drainage alone leads to recurrence). Antibiotics if secondary bacterial infection is present.
Fig. 23.3 - Squamous metaplasia of lactiferous ducts: keratin plug causes duct rupture, abscess, and fistula tract
Fig. 23.3 - Squamous metaplasia extending deep into a nipple duct causes keratin trapping, rupture, abscess formation, and a fistula tract opening at the areolar edge.

3. Duct Ectasia

Age/Setting: 5th-6th decade of life, multiparous females. NOT associated with cigarette smoking (distinguishes it from squamous metaplasia).
Clinical features:
  • Palpable periareolar mass
  • Thick, white nipple secretions
  • Occasional skin retraction
  • Pain and erythema are uncommon
  • Can mimic invasive carcinoma clinically and radiologically
Morphology:
  • Ectatic (dilated) ducts filled with inspissated secretions and numerous lipid-laden macrophages
  • Duct rupture triggers chronic periductal/interstitial inflammation (lymphocytes, macrophages, plasma cells)
  • Granulomas may form around cholesterol deposits
  • Subsequent fibrosis produces an irregular mass with skin and nipple retraction
Fig. 23.4 - Duct ectasia histology: ectatic duct filled with inspissated debris surrounded by chronic inflammation and fibrosis
Fig. 23.4 - Duct ectasia: chronic inflammation and fibrosis surround an ectatic duct filled with inspissated debris. The fibrotic response can produce a firm irregular mass that mimics invasive carcinoma.

4. Fat Necrosis

Etiology: ~50% have history of breast trauma or prior surgery. The rest may be spontaneous (no identifiable cause).
Clinical features: Closely mimics cancer - presents as:
  • Painless palpable mass
  • Skin thickening or retraction
  • Mammographic densities or calcifications
Morphology (evolving stages):
StageFindings
AcuteHemorrhagic, central liquefactive necrosis with neutrophils + macrophages
SubacuteProliferating fibroblasts + chronic inflammatory cells surround the area
LateGiant cells, calcifications, hemosiderin appear; lesion replaced by scar or encircled by fibrous tissue
GrossIll-defined, firm, gray-white nodules with small chalky-white foci

5. Lymphocytic Mastopathy (Sclerosing Lymphocytic Lobulitis)

Clinical features: Single or multiple hard palpable masses or mammographic densities. Dense collagenized stroma may make needle biopsy difficult.
Morphology:
  • Atrophic ducts and lobules with thickened basement membranes
  • Surrounded by a lymphocytic infiltrate
  • Densely collagenized stroma
Key associations:
  • Type 1 diabetes (diabetic mastopathy) - most common
  • Hashimoto thyroiditis
  • Hypothesized to have an autoimmune basis
Clinical significance: Must be distinguished from breast cancer.

6. Granulomatous Mastitis

Causes:
  • Systemic granulomatous diseases - granulomatosis with polyangiitis, sarcoidosis, tuberculosis
  • Idiopathic granulomatous lobular mastitis - occurs only in parous females; granulomas closely associated with lobules and may contain lipid vacuoles surrounded by neutrophils
  • Cystic neutrophilic granulomatous mastitis - similar histology; often caused by lipophilic Corynebacteria
  • Localized infections - mycobacteria or fungi (rare; mainly in immunocompromised patients or around breast prostheses/nipple piercings)
Treatment: Antibiotics and sometimes corticosteroids.

Summary Table

ConditionAge/SettingKey FeatureClinical Mimic
Acute MastitisLactating womenS. aureus/streptococciAbscess
Squamous MetaplasiaSmokersKeratin plug → fistulaAbscess, nipple inversion
Duct Ectasia5th-6th decade, multiparousWhite nipple dischargeCarcinoma
Fat NecrosisPost-trauma/surgeryChalky-white necrosisCarcinoma
Lymphocytic MastopathyDM type 1 / HashimotoDense collagenized stromaCarcinoma
Granulomatous MastitisParous femalesLobule-centered granulomasInfection/abscess
Key exam point: Duct ectasia, fat necrosis, and lymphocytic mastopathy can all mimic invasive carcinoma clinically and radiologically - biopsy is often required for definitive diagnosis.
  • Robbins, Cotran & Kumar - Pathologic Basis of Disease, p. 946-947
  • Schwartz's Principles of Surgery 11th Ed., p. 577
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