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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