Histologic subtypes of ductal intraepithelial neoplasia (DIN) of the breast: Characteristic associations and biology

Abstract

633 Background: Most invasive breast cancers are associated with more than one histologic subtype of DIN. The clinical and biologic significance of these DIN subtypes is under-appreciated. Methods: We reviewed 853 cases of DIN diagnosed at our University based Breast Center between 2003 and 2008, 568 (67%) of which were associated with an invasive cancer. Cases of pure invasive cancer without DIN were excluded. Results: A single histologic subtype was present in 41% of the cases, two subtypes in 43%, and three in 16%. The most common DIN subtypes present were solid (52%) and cribriform (50%), while the comedo (18%), micropapillary (11%), papillary (9%) and flat (6%) subtypes were less common. Comedo and solid DIN were frequently found together (Odds ratio [OR]) for coexpression 1.94, p< .001) as were micropapillary and papillary subtypes (OR 2.58, p< .005). Comedo DIN was much less likely to be found with papillary (OR .24, p< .005), flat (OR .34, p< .05), cribriform (OR .42, p< .001) or micropapillary (OR .48, p< .05) subtypes. We also examined multiple biological parameters and their association with the different DIN subtypes as shown in the table below. Solid and comedo subtypes tend to be hormone receptor negative, Her2 positive and high grade while the cribriform subtype tends to be hormone receptor positive, Her2 negative and low grade. Papillary and comedo DIN are most likely to be larger lesions. Papillary DIN is least likely to be associated with an invasive cancer. Conclusions: The histologic architecture provides clues to the underlying molecular changes and biological behavior of DIN. This study will begin to help us understand the molecular basis for the different histologic subtypes of DIN, their different clinical behaviors and tendencies to progress to invasive cancer. [Table: see text] No significant financial relationships to disclose.