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Breast Core Imprint Cytology: Key Learning from BAC Slide Club

Breast Core Imprint Cytology: Key Learning from BAC Slide Club

At the latest BAC Slide Club, Dr Ash Chandra presented a focused series of breast cytology cases highlighting the diagnostic value of core imprint cytology in symptomatic breast clinics.

What is Core Imprint Cytology?

Core imprint cytology involves making touch imprints from breast core biopsies to allow:

  • Immediate adequacy assessment
  • Rapid provisional diagnosis
  • Early triage for further testing

This approach is particularly useful in one-stop breast clinics, where patients present with symptoms such as lumps or pain.

 

Case 1: Fibroadenoma

Key features:

  • Branching epithelial fragments (“staghorn” pattern)
  • Numerous bare bipolar nuclei (myoepithelial/stromal)
  • Presence of stromal fragments

Interpretation:

  • Classic benign triad: epithelial + myoepithelial + stroma
  • Diagnosis: Fibroadenoma

Learning point:
The presence of a dual cell population and stroma is strongly supportive of benignity.

 

Case 2: Juvenile (Cellular) Fibroadenoma

Clinical context: 19-year-old with enlarging breast lump

Key features:

  • Marked hypercellularity
  • Large stromal fragments with embedded nuclei
  • Preserved dual cell population

Interpretation:

  • C3 (atypia) due to high cellularity
  • Differential: Fibroadenoma vs Phyllodes tumour

Learning point:
Hypercellularity alone does not imply malignancy, especially in young patients. Clinical and radiological correlation is essential.

 

Case 3: Papillary Lesion with Malignant Potential

Key features:

  • Papillary clusters with fibrovascular cores
  • Mixed epithelial and myoepithelial cells
  • Focal atypia and loss of cohesion

Interpretation:

  • C3/C4: Papillary neoplasm
  • Final diagnosis: Papillary carcinoma in situ within a benign lesion

Learning point:
All papillary lesions require excision, as cytology cannot reliably exclude malignancy.

 

Case 4: Mucinous Carcinoma

Clinical context: 68-year-old with enlarging lump

Key features:

  • Bland epithelial cells
  • Absent myoepithelial cells
  • Abundant extracellular mucin

Interpretation:

  • C5 (malignant)
  • Diagnosis: Mucinous adenocarcinoma

Learning point:
Loss of the dual cell population and presence of mucin are key indicators of malignancy.

 

Case 5: Suspicious for Phyllodes Tumour

Clinical context: 53-year-old with rapidly enlarging mass

Key features:

  • Highly cellular stromal fragments
  • Stromal atypia
  • Background benign epithelium

Interpretation:

  • C3: Phyllodes tumour not excluded

Learning point:
Distinguishing fibroadenoma from phyllodes tumour is often not possible on cytology or core biopsy alone—excision is required.

 

Clinical Value of Core Imprints

Core imprint cytology provides significant clinical advantages:

  • Rapid reassurance for benign cases (majority ~80%)
  • Early identification of malignancy
  • Ability to pre-request receptor studies (ER/PR/HER2)
  • Faster patient pathway and earlier treatment planning

 

Service Insights

  • Established for ~10 years at Guy’s & St Thomas’
  • Delivered by cytopathologists and trained BMS
  • Also applied in thoracic and bronchoscopy services
  • Increasing demand may require telecytology solutions in future

 

Key Takeaways

  • The dual cell population is central to benign diagnosis
  • Hypercellularity ≠ malignancy
  • Papillary lesions always require histological excision
  • Absence of myoepithelial cells is a red flag for malignancy
  • Core imprint cytology is a valuable adjunct, not a replacement for histology