Pathology Thread

V. Benign Neoplasms

Objectives:

After completing this section you will be able to:

• list the common benign neoplasms of the breast
• describe clinical features
• describe histologic features and identify lesions
• predict risk for subsequent breast cancer associated with each lesion

1. Intraductal papilloma

This is a papillary tumor that arises from the duct epithelium and is practically the only lesion that arises in large ducts. It arises more often in the central part of the breast from the lactiferous ducts (75%) but can occur in any quadrant. It is more commonly solitary, consisting of a single tumor in one duct, but multiple discrete tumors, usually in contiguous branches of the ductal system may occur.

Nipple discharge, which may be bloody, is the most common presentation for central papillomas and less commonly of peripheral tumors. A subareolar mass may be palpable. Multiple papillomas develop more often peripherally and typically present as a palpable lesion. Age range is from 30 to 50 years. The average size of a solitary papilloma in a major lactiferous duct is2-3cm. Multiple papillomas typically form masses greater than 2 cm.

The tumor appears microscopically as complex branching fronds of stroma supporting a layer of epithelium composed of epithelial and myoepithelial cells. The epithelial cells are cuboidal to columnar and do not show pleomorphism or mitotic activity.

Intraduct papilloma showing complex, branching fronds within dilated duct.

Intraduct papilloma. Medium power view.Note fibrous tissue core tissue.

Intraduct papilloma showing the two-cell layer epithelium

Reported frequency of carcinoma subsequent to excision of papilloma has been less than 5% and nearly half occurred in the contralateral breast. Greater risk has been shown in women with multiple papillomas.

2. Fibroadenoma

This is the commonest benign tumor of the breast and is composed of both epithelial and stromal tissue derived from the TDLU. They are usually found between ages 20 to 35 years although they occur at any age within the reproductive age. Fibroadenoma is more common, develops at a younger age and is more likely to recur in blacks than whites. The tumor presents as a spherical, rubbery nodule, which is sharply circumscribed from the surrounding breast tissue and so is freely movable and can be shelled out. It is usually between 2 and 3 cm but in some adolescents may attain great size and called giant fibroadenoma. It may increase in size during pregnancy and cease to grow after menopause. The tumor is usually solitary but may be multiple and involve both breasts. The cut surface is pearl-white.

Fibroadenoma (shelled out).

Histologically, the tumor is composed of a mixture of ducts and fibrous connective tissue. The ducts may take one of two patterns, open, round-to-oval with the usual double layer or multiple layers of cells (pericanalicular type) or be compressed by stroma to form slit-like, curvilinear clefts (intracanalicular type). Both patterns may coexist in the same tumor. The stroma varies from loose and myxoid to dense and hyalinized collagen.

Fibroadenoma showing proliferation of ducts and stroma.

The tumor is completely benign. Since it arises from the TDLU, the tumor may show other changes seen in the TDLU such as lactational change during pregnancy, apocrine metaplasia or epithelial hyperplasia, It may undergo infarction during pregnancy or lactation or calcify after menopause. Rarely, carcinoma may arise within a fibroadenoma. The predominant type has been lobular carcinoma. There is some indication that "complex" fibroadenomas with large cysts, sclerosing adenosis, epithelial calcifications, and apocrine metaplasia increase the risk of subsequent carcinoma.