What is Intraductal Papilloma?
Intraductal papilloma is a benign breast tumor that grows within the milk ducts, typically presenting with pathologic nipple discharge (spontaneous, unilateral, single-duct, serous or bloody) or as an incidental finding on imaging. 1
Definition and Pathologic Features
Intraductal papilloma (IDP) is a benign proliferative lesion characterized by:
- Papillary growth pattern within breast ducts, consisting of fibrovascular cores lined by epithelial and myoepithelial cells 2
- Solitary lesions typically occur in the central/subareolar ducts of women aged 30-50 years 1
- Size typically >1 cm to be clinically significant, though smaller lesions can be detected on imaging 2
Clinical Presentation
The most common presentations include:
- Pathologic nipple discharge (spontaneous, unilateral, single-duct, serous or bloody) - the classic presentation requiring evaluation 1
- Palpable subareolar mass in some cases 1
- Incidental finding on screening mammography or ultrasound 3
Diagnostic Approach
Imaging Evaluation
- Mammography (first-line for patients ≥40 years) may show asymmetrically dilated ducts, circumscribed subareolar mass, or grouped microcalcifications 1
- Ultrasound is more sensitive than mammography and should be performed in all patients with pathologic nipple discharge, typically showing smooth, hypoechoic intraductal masses 1, 3
- MRI often shows strong enhancement with type 2 or 3 time-intensity curves, which can mimic malignancy and lead to inconclusive results 3
Tissue Diagnosis
- Core needle biopsy is essential for definitive diagnosis, as imaging alone cannot reliably distinguish benign from malignant lesions 1
- Histologic classification includes: micropapilloma, fragmented IDP, IDP without atypia, and IDP with atypia 4
Malignancy Risk and Management
Upgrade Rates to Malignancy
The risk of finding cancer at surgical excision varies significantly:
- IDP without atypia: 0-33% upgrade rate depending on lesion characteristics 2, 5
- IDP with atypia: 33-45% upgrade rate to ductal carcinoma in situ (DCIS) or invasive carcinoma 5, 6
- Overall upgrade rate: 2.3-41% across all studies, with higher rates when atypia is present 2, 5, 6
Treatment Recommendations
Complete surgical excision is the standard management for intraductal papillomas diagnosed at biopsy, due to the 3-14% risk of malignancy upgrade at final pathology. 1
Specific management based on lesion characteristics:
- IDP with atypia: Surgical excision with clear margins is mandatory due to 33-45% upgrade risk 5, 6
- IDP without atypia, mass-associated: Vacuum-assisted excision or surgical excision recommended 6
- Non-mass-associated IDP without atypia: Conservative follow-up with ultrasound may be reasonable for lesions <1 cm with careful pathologic-radiologic correlation 4
- Small solitary IDP (<1 cm) without atypia: Close ultrasound follow-up may be considered, as upgrade rate is only 0.9% 2
Critical Clinical Pitfalls
- Do not rely on imaging characteristics alone - tissue diagnosis is mandatory, as benign-appearing lesions on MRI can harbor malignancy 1, 3
- Any discordance between imaging and pathology findings requires surgical excision 1
- All IDPs with atypia on core biopsy must be excised, regardless of size or imaging appearance 5, 6
- Even IDPs without atypia can upgrade to malignancy (33% in one series), so excision should be considered when clinical or imaging findings cannot rule out malignancy 5