Lobular in situ neoplasia

Premalignant disease of the lobules- Lobular in situ neoplasia encompasses two old-term conditions:

  • Atypical lobular hyperplasia (ALH)- <50% of the lobule involved
  • Lobular carcinoma in situ (LCIS)- >50% of the lobule involved

Clinical features/Epidemiology

  • Frequently multifocal and bilateral
  • 0.5-4% of all benign biopsies (relatively rare)
    • This decreases further after the menopause (hormone driven neoplasia)
  • Normally not palpable/grossly visible
  • May calcify and present at mammography as an incidentle finding / screening

Pathology

  • Intralobular proliferation with characteristic features:
    • Small intermediate sized nuclei
    • Solid proliferation
    • Intracytoplasmic lumens/vacuoles
    • Oestrogen receptor (ER) positive / E-cad negative
  • NB IMPORTANT:
    • 20% of cases with lobular neoplasia at core biopsy actually have a higher grade lesion on open excisional biopsy (i.e. definitive cancer)
      • 8-fold increase in risk of carcinoma if LISN present (i.e. a genuine precursor to cancer)
      • This increase is time dependent too:
        • ALH- 10% 5-year risk
        • ALH and a FHx- >20% 5 year risk
        • LCIS +/- FHx- 20% 5 year risk

Management

  • If diagnosed on core biopsy- excise and follow up
  • If diagnosed on excision biopsy- follow up
  • Tamoxifen is usually used in these patients too
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