About Benign Breast Tumors

Overview

The breast is broadly composed of glandular tissue and the connective tissue that supports it. The glandular tissue consists of lobules that produce breast milk and ducts that serve as passageways, connecting to the nipple-areolar complex. At the tip of the nipple, there are about 15 to 20 openings through which breast milk collected in the collecting ducts flows out.

When puberty begins, the breasts develop markedly. Estrogen secreted from the ovaries and progesterone secreted during ovulation stimulate the growth of glandular tissue, and hormones such as growth hormone, thyroid hormone, and insulin also play a role. During this period, not only quantitative changes but also changes in the elasticity of the connective tissue occur, and blood vessels become more abundant and fat increases. The size of the nipple and areola increases, they become more prominent, and pigmentation increases. After menopause, proliferation of the glandular tissue decreases, and connective tissue components such as collagen, elastic fibers, and fat also change.

Benign breast tumors that can occur in the breast include cysts, fibroadenomas, hamartomas and adenomas, papillomas and papillomatosis, radial scars, and fat necrosis.

Types of Benign Breast Tumors

[ Cyst ] A cyst is commonly known as a "fluid-filled lump" and refers to an empty mass with fluid accumulated inside and lined on the outside by epithelial cells. Its size varies widely, from very small lesions that cannot be felt to masses large enough to be palpated. It is found in about one in 14 women, and 50% of cysts are multiple or recurrent. The mechanism by which cysts develop is not well known, but they are thought to form when lobules and microducts expand and become damaged, and cysts can be influenced by female hormones secreted from the ovaries, causing changes in size according to the menstrual cycle.

Most cysts occur mainly in women over 35 years of age, and their frequency increases until menopause and then decreases afterward. New cysts that develop after menopause are mostly caused by exogenous hormone use. Breast cancer accompanying a cyst is extremely rare, and there is no evidence that cysts increase the incidence of breast cancer.

[ Fibroadenoma and Related Tumors ] Fibroadenoma is a benign tumor that often occurs in teenage and women in their 20s and arises from the epithelium and stroma of the terminal duct-lobular unit. It is the most common breast disease in Korean women and a breast tumor that occurs more often in young women under 30. Clinically, it is often found as a firm, round mass that moves freely, and its size may increase over several months. Fibroadenoma is thought to arise from stimulation by estrogen, and it is known that growth usually stops once it reaches a size of 2 to 3 cm. It is not easily distinguished from breast cysts on mammography, but it can be easily differentiated from cysts by ultrasound. It is not clear whether fibroadenoma significantly increases the risk of breast cancer, but, like any other part of the breast, malignant transformation can rarely occur in the epithelial tissue within the tumor. Therefore, histologic examination should be performed to distinguish it from carcinoma.

[ Hamartoma and Adenoma ] Breast hamartoma is a very rare benign breast disease, mainly found in older women. It may be palpated as a distinct mass, but it may also present as an increase in the size of both breasts. It appears as a mass composed of fat, covered by a thin radiolucent pseudocapsule on mammography, with varying proliferation of ducts, lobules, stroma, and adipose tissue. Adenomas can be divided into tubular adenoma and lactating adenoma. Tubular adenoma is found in young women as a mass very similar to fibroadenoma and is composed only of proliferating epithelial cells. Lactating adenoma is found during pregnancy or immediately after delivery and is composed of secretory glands.

[ Fat Necrosis ] Breast fat necrosis is a relatively common condition caused by trauma, previous surgery, radiation therapy, or paraffin or silicone injection. Because it appears as one or more firm masses with unclear borders, it can resemble carcinoma.

[ Papilloma and Papillomatosis ] Papillomatosis refers to a polyp-like lesion with one or several lesions occurring at the same time and showing a villous structure lined by epithelial cells, mainly occurring in the ductal system when solitary and in the terminal duct-lobular unit when multiple. There is no direct association between malignant breast tumors and benign papillary lesions, but one study reported that when papillomas diagnosed by core needle biopsy were accompanied by atypia, papillary carcinoma was found in about 20% of cases.

Solitary papillomas commonly occur in women around the premenopausal period, are located near the nipple, and are usually smaller than 1 cm. Multiple peripheral papillomas occur at a younger age than solitary papillomas, rarely cause nipple discharge, often arise in peripheral ducts, and occur bilaterally in about 15% of patients.

[ Sclerosing Adenosis ] Sclerosing adenosis of the breast is characterized by proliferation of the glandular and connective tissues, resulting in lobular distortion, fibrosis, and calcification. It is the most common lesion among patients undergoing breast biopsy because of calcifications. It occurs mainly in women of reproductive age and around menopause, and since it usually does not form a clear mass, it is often found incidentally.

[ Radial Scar and Complex Sclerosing Lesion ] Radial scar and complex sclerosing lesion are benign proliferative lesions with complex sclerosing features such as central sclerosis, epithelial hyperplasia, apocrine metaplasia, and papilloma formation. They mainly occur at the branching point of the terminal duct-lobular unit, and lesions 1 cm or smaller are called radial scars, while larger lesions are called complex sclerosing lesions.

So far, I have explained benign breast tumors. In the next part, we will look at the symptoms of benign breast tumors.

Source: National Health Information Portal, Korea Disease Control and Prevention Agency