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HGPIN versus AIP versus IDC-P


Feature

HGPIN

AIP

IDC-P

Definition

Proliferation of atypical epithelial cells within preexisting ducts/acini without invasive features.

Atypical intraductal proliferation falling short of IDC-P criteria; includes "atypical cribriform proliferation" and "atypical intraductal proliferation suspicious for IDC-P".

Malignant cells filling and expanding preexisting ducts/acini, often associated with invasive carcinoma.

Histology

Cytological atypia with preservation of normal architecture; loose or micropapillary architecture possible.

Cribriform or solid proliferation without definitive features of IDC-P; lacks the architectural and cytological complexity of IDC-P.

Solid/dense cribriform or loose cribriform pattern with marked cytological atypia, often with comedonecrosis.

Cribriform Pattern

Existence is controversial, diagnosis not recommended on needle biopsy.

Often overlaps with previous cribriform HGPIN but does not meet IDC-P criteria.

Solid/dense cribriform pattern diagnostic; lumen-spanning proliferations commonly included.

Cytological Atypia

Mild to moderate; lacks marked pleomorphism or hyperchromasia.

Intermediate atypia, suspicious but not conclusive for malignancy.

Marked pleomorphism, hyperchromasia, mitoses, apoptotic bodies.

Comedonecrosis

Absent.

Absent.

Strongly associated; a key diagnostic feature.

Differential Diagnosis

Important to distinguish from IDC-P due to clinical implications.

Considered a precursor lesion; requires follow-up but does not meet IDC-P criteria.

Requires differentiation from invasive carcinoma; high-risk lesion requiring aggressive management.


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