A malignant tumour of breast epithelial cells

Aetiology

Risk factors

• Female sex and age are the most significant risk factors
• Mutations to certain genes are well-documented risk factors, most importantly the tumour suppressor genes BRCA1 and BRCA2
• Family history in a first degree relative
• Previous benign disease
• Geographic variation (more common in developed countries)
• Degree of exposure to unopposed oestrogen has also been well-documented to cause an increase in risk to develop breast cancer
  • Early menarche
  • Late menopause
  • Nulliparous women
  • First pregnancy after 30 years of age
  • Oral contraceptives or HRT use
• Lifestyle factors:
  • Obesity
  • Physical activity is protective
  • Alcohol consumption
  • Diet
  • NSAID lower risk
  • Smoking

Pathophysiology

• Arises in the glandular epithelium of the terminal duct lobular unit (TDLU)
• It is an adenocarcinoma but is usually just referred to as ‘breast carcinoma’

Histological classification

Invasive cacinoma of the breast can be classified into:

• Invasive ductal carcinoma (75-85%)
  • Can be further classified into tubular, cribriform, papillary, mucinous (/colloid), or medullary carcinomas, all showing distinct patterns of growth
• Invasive lobular carcinoma (10%)
  • Characterised by a diffuse (stromal) pattern of spread that makes detection more difficult
• Other subtypes (5%), such as medullary carcinoma or colloid carcinoma
• Other factors used in classification:
  • Gene expression profiling
  • Hormone receptor expression - oestrogen receptor, progesterone receptor, HER2

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