Table 3. Factors influencing the upgrade to malignancy in intraductal papilloma without atypia in the multivariate analysis.

Characteristic	OR	95% CI	p-value
Age ≥ 55 yr	4.351	1.576–12.071	0.005
Size > 1 cm	4.236	1.012–10.256	0.001
Breast density* ( > 50%)	0.481	0.133–1.529	0.107
Palpable mass	0.590	0.223–2.605	0.632
Nipple discharge	1.952	0.642–11.062	0.285

OR=odds ratio; CI=confidence interval.

^*Mammographic density by Breast Imaging Reporting and Data System classification system (breast density: type 1, almost entirely fat, glandular tissue is less than 25%; type 2, scattered fibroglandular tissues, ranging from 25% to 50% of the breast; type 3, heterogeneously dense parenchyma, ranging 51% to 75% of the breast tissue; type 4, the breast contains greater than 75% glandular and fibrous tissue).