Intraductal papillomas are a group of benign tumors of the breast that stem from the epithelium of the lactiferous ducts (i.e., a system that links the lobules of the mammary gland with the tip of the nipple). The incidence of these changes is low and usually in the range of 2 to 3%, affecting women between 30 and 77 years of age.
There are two general types of intraductal papillomas: central and peripheral. The central type is characteristic for the subareolar region of the breast, usually appearing in solitary fashion during perimenopause. On the other hand, peripheral intraductal papillomas develop in young women, are often multiple, and emerge inside the terminal duct-lobular unit.
Clinical Presentation and Pathological Features
Clinically, intraductal papillomas most often present as pathological nipple discharge, accounting for about 5% of all women that attend symptomatic breast clinics. Such discharge can be clear, serous, colored, or blood stained. This arises as a result of twisting of papilloma and subsequent ischemia with necrosis and intraductal bleeding.
Still, as this symptom is not sufficient for establishing a correct diagnosis, experts have to rely on histologic features to delineate different findings. The most important distinguishing feature between benign intraductal papilloma and atypical papillomas or its malignant counterparts (such as papillary intraductal carcinoma) is the epithelium.
In benign intraductal papillomas, the eptihelial layer is supported by myoepithelial cells, whereas papillary carcinoma show disrupted or completely absent myoepithelial cell layer. Nevertheless, a great deal of controversy surrounds their diagnosis, as intraductal papillomas can be associated with a plethora of histological types and various characteristics.
Generally, intraductal papilloma is characterized by fibrovascular cores that branch and protrude into the ductal lumen. Those cores are composed of fibrous branches with centrally located vessels lined by endothelial cells and a rather uniform myoepithelial cell layer that faces the lumen.
Different Evaluation Techniques
Cytological diagnosis of intraductal papilloma can be established by either examining the serous or bloody nipple secretions or by using fine-needle aspiration of a palpable lesion. Benign intraductal papillomas most often yield cellular aspirate that contains clusters of ductal cells with papillary configuration.
Ductography represents a safe and simple method for visualizing the affected duct systems, and it reveals intraductal papillomas as filling defects within the dilated ducts. Solitary papillomas are usually seen in the collecting ducts, whereas multiple papillomas are often noted in the branching ducts (sometimes even leading to the cystic dilatation of the ductal system).
On magnetic resonance imaging, intraductal papillomas range from small luminal masses to irregular enhancing lesions that are often hard to discriminate from invasive malignancy. Ultrasound techniques with 3D views represent a good complementary approach in visualizing intraductal papillomas and other disorders inside the ducts.
Management of the Disease
Central intraductal papillomas that are not associated with epithelial atypia are considered benign lesions of the breast. There is only a slight increased risk for subsequent development of breast cancer, which is comparable to the risk in patients with proliferative fibrocystic disease of the breast without atypia.
Thus, the patients can be monitored clinically without the need for surgical excision. Nevertheless, individuals with multiple intraductal papillomas do have a higher risk of developing breast cancer, so annual review with repeated digital mammography should be recommended.
Microdochectomy (an operation to remove a lactiferous duct that produces a pathological nipple discharge) remains an effectual surgical procedure for managing intraductal papillomas. Intraductal biopsy guided by mammary ductoscopy can be both diagnostic and curative approach, although the latter requires additional validation in the quotidian clinical practice.