Acute Mastitis

• Acute inflammation of the breast, typically found in post-partum or pre-menopausal women

  
  

• Microbial causes:

  
  
  • S. aureus: Localised abscess
  • Streptococcus spp.: Diffused infection
    

• Pathogenesis:

  
  
  • Cracked, inflamed nipple allows entry of microbe
  • Proliferation of microbe in stagnant milk
  • Acute inflammation - resulting in abscess formation
    

• Clinical Features:

  
  
  • Breast appears erythematous, painful
  • Fever
    

• Treatment:

  
  
  • Incision and drainage
  • Antibiotics
  • Excision

Breast Implants/Injections

• Types:
  
  • Paraffin injections, implants, autologous tissue
• Pathological Effects:
  
  • Fibrosis around implant
  • Foreign body inflammatory reaction to leakages
• Morphology:
  
  • Empty spaces in histological section representing areas of paraffin
  • Surrounded by foreign body giant cells and histiocytes

Non-proliferative Breast Changes

• Aka fibrocystic changes of the breast
• Epidemiology:
  
  • Produces symptoms in at least 10% of women
  • Occurs during reproduction decades, peak incidence in premenopausal decade

• Types of Alterations:

  
  
  • Cysts and apocrine metaplasia
    
    • Unopened cysts containing turbid blue fluid (blue domed cysts)
    • Cysts lined by flattened atrophic epithelium or by metaplastic apocrine cells
    • Apocrine cells have abundant eosinophilic cytoplasm and round nuclei
  • Fibrosis
    
    • Due to chronic inflammatory reaction to contents of cysts released when cysts rupture
  • Adenosis
    
    • Increase in the number of acini per lobule
      

• Clinical Features:

  
  
  • Presents as a lump
  • No increased risk of invasive breast carcinoma
    

-Without Atypia

• Lesions characterised by proliferation of ductal epithelium (and/or stroma) without features suggestive of carcinoma in-situ (cytologic nor architectural)
• Types of lesions:
  
  • Epithelial hyperplasia
    
    • More than 2 cell layers in epithelial lining of ducts
  • Sclerosing adenosis
    
    • No. of acini per terminal duct at least 2x that of uninvolved lobules
  • Large duct papillomas
    
    • Exophytic growths with fibrovascular cores lined by luminal and myoepithelial cells
    • Grow within the lumen of lactiferous ducts (hence may present with bloody nipple discharge)
• Clinical Features:
  
  • Slightly increased risk (1.5 to 2x) of invasive breast carcinoma

-With Atypia

• Types of Lesions:
  
  • Atypical ductal hyperplasia
    
    • Histologic resemblance to ductal CIS except that it is limited and only partially fills ducts
  • Atypical lobular hyperplasia
    
    • Histologic resemblance to lobular CIS except that cells do not fill or distend more than 50% of acini within a lobule
• Clinical Features:
  
  • Significantly increased risk (5x) of invasive breast cancer

Fibroadenoma

• Highest prevalence in young women (peak around 25yo)
• Morphology:
  
  • Gross:
    
    • Firm, well-defined mobile lump (mouse in the breast)
    • May be multiple and bilateral
  • Histologically:
    
    • Proliferation of glandular and stromal elements
      
      • Pericanalicular or intracanalicular pattern - no prognostic significance
    • Cellular, delicate myxoid stroma (resembles normal intralobular stroma of breast)
• Clinical Features:
  
  • Slow-growing tumour
  • Risk of malignancy based on degree of epithelial hyperplasia
  • Can recur, may occasionally regress spontaneously

Phyllodes Tumour

• Histology:
  
  • Both glandular and stromal components
  • Frondlike architecture
  • Stroma more cellular than that of fibroadenoma
  • Not fully circumscribed: tongues of tumour going into adjacent tissue (hence require 1cm margin in excision to prevent recurrence)
• Clinical Features:
  
  • Higher risk of malignancy than fibroadenoma - in which it will become a sarcoma (proliferating stromal elements overrunning the epithelial components of the original benign tumour)

Risk Factors

• Race (Caucasian, Jew, Parsi)
• Age (Perimenopausal)
• Socioeconomic status (high)
• Weight (obese)
• Previous breast diseases
• Family Hx of breast cancer
  
  • BRCA1 and BRCA2
    
    • DNA repair genes for double strand breaks.
    • Mutations account for 25% of familial breast cancers
• Ovarian activity (early menarche, late menopause)
• Exogenous oestrogen (oral contraceptives, hormone replacement therapy)
• Nulliparity
• Lack of breastfeeding
• Proliferative diseases of breast

Classification

• Carcinoma in-situ

  
  
  • Ductal CIS (+ Paget's disease)
  • Lobular CIS
    

• Invasive carcinoma

  
  
  • Invasive ductal - wastepaper basket category
  • Invasive lobular
  • Special types:
    
    • Tubular
    • Mucinous
    • Medullary
    • Lobular
      
      

Paget's Disease

• Rare manifestation of ductal CIS involving the nipple
• Pathogenesis:
  
  • Extension of DCIS along ducts within the epithelial layer to the area under the skin over nipple
• Appearance:
  
  • Unilateral
  • Exfoliation/ulceration of nipple
  • Erythematous eruption with a scale crust
  • Large, atypical cells with clear cytoplasm