Classification of ductal carcinoma in situ (DCIS)

Last revised by Joshua Yap on 10 May 2023

The new pathological classification of DCIS (ductal carcinoma in situ) is based on cytonuclear atypia, degree of necrosis, size, and distance from margin/architecture. Low and intermediate grades DCIS require cytologic, architectural and size criteria to be met but high-grade DCIS requires only cytologic criteria; this is as follows:

  • low grade

    • round, regular to mildly irregular nuclei up to 2-3 times the size of a red blood cell

    • no comedo necrosis

  • intermediate grade

    • round, regular to mildly irregular nuclei up to 2-3 times the size of a red blood cell

    • substantial comedo necrosis

  • high grade

    • pleomorphic nuclei more than 3 times the size of a red blood cell

    • substantial comedo necrosis usually present, but not required for the diagnosis

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