Breast Pathology: Ductal carcinoma in situ

Is a clonal non invasive proliferation in breast involving ducts (although may involve lobules termed cancerization). A precursor of invasive ca. Most commonly seen as microcalcifications – rod shaped, branching in high grade and granular in low grade. Tx WLE with rim of normal + DXT. ?completeness of excision – 10mm although some accept 2mm. Occasionally mastectomy. Smooth muscle myosin and p63 IHC to identify myoepithelial layer to differentiate from invasive malignancy. Homogenous expression of basal, luminal cytokeratins and ER due to it’s clonal nature compared to UEH. Recurrences at site of excision of dcis is thought to be residual dcis and often presents as invasive disease.

High grade Dcis

  • large, pleomorphic cells with course chromatin. Nuclei >x2.5 the size of rbc,
  • Prominent nucleoli, mitoses
  • necrosis

Low grade Dcis

  • evenly spaces, small regular cells with round nuclei x1.5-2 rbc in size
  • typically micropapillary, cribriform architecture
  • well defined cell boundaries
  • shows polarisation

Intermediate Dcis

When dcis cannot be assigned to low grade or high grade.

Rarer subtypes:

Apocrine Dcis: abundant granular cytoplasm and prominent nucleoli. Typically high grade with necrosis.

Neuroendocrine Dcis:

  • granular cytoplasm, cells may resemble carcinoid
  • solid or pseudorosette architecture
  • polygonal/spindle cells (spindle cells may mimic streaming of UEH)
  • assoc with papillary cis & Dcis
  • strong ER staining +/- neuroendocrine markers

Clear cell Dcis

Signet ring Dcis

Clinging Dcis (low grade termed flat epithelial atypia)

Microinvasive Dcis- <1mm invasive focus. Do myoepithelial markers to confirm also consider cancerisation of  lobules – do further levels.

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