Not all breast conditions or tumors are cancerous. Benign (noncancerous) breast conditions are common and are not life-threatening, although some may increase the risk of developing breast cancer in the future. Benign breast conditions may cause similar symptoms as breast cancer[MB1]  and also may be discovered during routine mammogram screening. Additional testing [MB2] such as lab tests, imaging tests, and biopsies [MB3] will be performed to determine whether the condition is cancerous or not. Some examples of noncancerous breast conditions are fibrosis and simple cysts, fat necrosis and oil cysts, lobular carcinoma in situ (LCIS), hyperplasia (also known as epithelial hyperplasia or proliferative breast disease), adenosis (also known as aggregate adenosis, tumoral adenosis, or adenosis tumor), fibroadenomas, intraductal papillomas, granular cell tumors, mastitis, duct ectasia (also known as mammary duct ectasia), and some phyllodes tumors.[1]

Fibrosis means a large amount of fibrous tissue, the tissue that makes up scar tissue and ligaments. Areas of fibrosis may feel rubbery, firm, or hard. Cysts are fluid-filled sacs that may feel like a movable lump. Fibrosis and cysts are both common breast conditions that many women develop at some point in their lives. They are most common when a woman is of child-bearing age but can occur at any time. Cysts often grow in size and become painful just before a woman’s menstrual cycle due to hormone changes. Fibrosis and cysts can lead to symptoms such as breast lumps, swelling, tenderness, pain, and nipple discharge. If one of the lumps feels especially firm, an ultrasound may be done to determine the contents of the lump. A lump that is filled with fluid (simple cyst) is most likely not cancerous, but a lump filled with fluid and solid components (complex cyst) or a completely solid lump may needed to be biopsied to determine whether it is cancerous. Fibrosis and simple cysts both do not increase the risk of developing breast cancer.[2]

Fat necrosis is more common in women with very large breasts and occurs when an area of the fat tissue is damaged, usually as a result of injury. Most of the damaged fat tissue will form scar tissue, but some may also release its contents, forming a collection of greasy fluid called an oil cyst. Fat necrosis and oil cysts may cause lumps and the skin around the lump may look red, thick, or bruised. An oil cyst can usually be differentiated using an ultrasound, but a biopsy may need to be done to confirm. Fat necrosis and oil cysts both do not increase the risk of developing breast cancer.[3]

LCIS does not usually cause a lump that can be felt or detected with mammogram testing, so it is almost always discovered through a biopsy. LCIS is defined as having cells that look like cancer cells growing in the milk lobules, but they do not invade through the walls of the lobules. LCIS is not considered to be breast cancer because it rarely becomes invasive. However, having LCIS increases the risk of a woman developing invasive breast cancer in the future by 7-12 times. It is important, therefore, for women with LCIS to receive regular breast cancer screening tests. However, if the LCIS has cells that look more abnormal than normal (pleomorphic), it is more likely to turn into an invasive cancer and may be removed with surgery.[4]

Hyperplasia is an overgrowth of cells that line the milk ducts (ductal hyperplasia) or milk lobules (lobular hyperplasia). Usual hyperplasia means the cells look normal, while atypical hyperplasia (also known as hyperplasia with atypia) means the cells look abnormal. Hyperplasia does not usually cause a lump that can be felt but can usually be seen by mammogram testing and confirmed with a biopsy. If the hyperplasia is mild and of the usual type, it does not increase the risk of developing breast cancer. If the hyperplasia is moderate or severe and of the usual type, the risk of developing breast cancer increases by 1 ½ to 2 times. If the hyperplasia is atypical, the risk of developing breast cancer increases by 4 to 5 times. Women with atypical hyperplasia should therefore consider seeing a healthcare provider every 6-12 months for a breast exam and get a yearly mammogram.[5]

Adenosis is when the milk lobules are large and there are more lobules than usual. If there are many enlarged lobules close together, adenosis may cause a lump. Mineral deposits (calcifications) which show up during mammogram testing can occur as a result of breast cancer or adenosis, so a biopsy may be needed for confirmation. Adenosis is often discovered when a woman receives a biopsy for another breast condition such as fibrosis or cysts. For most types of adenosis, it is not believed to increase the risk of developing breast cancer. However, a type of adenosis where the enlarged lobules are distorted by scar tissue (sclerosing adenosis) may slightly increase the risk of developing breast cancer.[6]

Fibroadenomas are benign breast tumors made up of glandular tissue and connective tissue. Fibroadenomas are most common in women in their 20s and 30s and tend to shrink in postmenopausal women. Some fibroadenomas are too small to be felt, but others can be felt. They can be moved under the skin and can feel firm or rubbery, but they are not tender to the touch. Fibroadenomas can be found using imaging tests such as an ultrasound or mammogram, and a biopsy will likely be needed for confirmation. Simple fibroadenomas look the same throughout when looked at under the microscope, while complex fibroadenomas have changes in appearance. Complex fibroadenomas tend to be larger and occur in older women. Simple fibroadenomas are not believed to increase the risk of developing breast cancer much, if at all. Complex fibroadenomas, on the other hand, may increase this risk slightly more. Women with fibroadenomas should receive regular breast exams and screening tests to make sure the fibroadenomas are not growing. If the fibroadenomas are growing, many doctors recommend removing them in case it is cancer causing the changes.[7]

Intraductal papillomas, wart-like tumors that grow in the milk ducts, are made up of gland tissue, fibrous tissue, and blood vessels. There may be one tumor (solitary papilloma) or multiple tumors (multiple papillomas). Solitary papillomas usually grow in the large milk ducts near the nipple and can cause a small lump behind or next to the nipple, pain, and clear or bloody nipple discharge. Multiple papillomas usually grow in the small milk ducts further from the nipple and are therefore less likely to cause nipple discharge. Papillomatosis is when there are very small areas of cell growth in the milk ducts that are not large enough to be considered papillomas. Ultrasounds, mammograms, and ductograms (x-rays of the milk ducts) can detect papillomas. A biopsy may be done if the papilloma is large enough to be felt. Having a solitary papilloma does not increase the risk of developing breast cancer if no other breast conditions are present such as atypical hyperplasia. Having multiple papillomas slightly increases the risk of developing breast cancer.[8]

It is believed that granular cell tumors start in early forms of nerve cells. These tumors are rarely found in the breast and are almost never cancerous. When they are found in the breast, granular cell tumors are usually located in the upper, inner part of the breast and can typically be felt as a firm lump under the skin that can be moved. However, it is also possible for these tumors to be attached to the skin or chest wall. A mammogram or ultrasound can be used to detect granular cell tumors in the breast, and a biopsy is usually needed for confirmation because these tumors can look similar to cancer in imaging. Granular cell tumors in the breast are not linked to a higher risk of developing breast cancer. Despite being benign, granular cell tumors are typically surgically removed along with a margin of surrounding tissue to keep them from recurring.[9]

Mastitis is inflammation of the breast, typically due to infection. Breastfeeding women are most commonly affected, but it can occur in anyone. Common causes of infection are a clogged milk duct, milk not draining fully from the breast, or broken nipple skin. Symptoms of infection may include a breast that is red, painful, warm, or swollen as well as a fever, headache, or general flu-like symptoms. Mastitis is diagnosed through a breast exam and can be treated with antibiotics and emptying any milk from the breast. Inflammatory breast cancer can have similar symptoms to mastitis and should be tested for with a biopsy if antibiotic treatment is not helping symptoms within a week or so. Having mastitis does not increase the risk of developing breast cancer.[10]

Duct ectasia occurs when a milk duct widens and its walls thicken, which may cause the duct to get blocked and fluid to build up. Duct ectasia is most common in women who are getting close to menopause but may occur in postmenopausal women as well. It usually causes no symptoms and may be discovered when a woman gets a biopsy for another breast condition. When symptoms do occur, duct ectasia can cause thick, sticky nipple discharge, red and tender nipple and nearby breast tissue, and inward pulling of the nipple. If there is scar tissue around the abnormal duct, it can cause a lump which may require a biopsy for confirmation. These changes to the milk ducts can also be viewed with a mammogram or ultrasound. Duct ectasia does not increase the risk of developing breast cancer.[11]

Phyllodes tumors are rare breast tumors that start in the connective tissue. About 75% of these tumors are benign, and they are most common in women in their 40s and women with the rare inherited disorder Li-Fraumeni syndrome. Phyllodes tumors are usually felt as a lump under the skin and can be painless or painful. They tend to grow quickly and can stretch the skin. These tumors can be found using an ultrasound or mammogram, but often appear similar to fibroadenomas. A biopsy is therefore typically needed for confirmation and to determine if the phyllodes tumor is cancerous or not. Benign phyllodes tumors do not increase the risk of developing breast cancer. Despite being noncancerous, benign phyllodes tumors are typically surgically removed along with a margin of surrounding tissue to keep them from recurring.[12]

Some other less common benign breast conditions include radial scars (also known as complex sclerosing lesions), lipoma, hamartoma, hemangioma, hematoma, adenomyoepithelioma, and neurofibroma.[13] Radial scars look like scars under the microscope, but are actually benign, tumor-like lesions.[13,14] If these lesions are large enough, they may look like cancer on a mammogram or even on a biopsy, and many doctors recommend surgery to remove them. Radial scars seem to be linked to a slight increase in the risk of developing breast cancer.[13]

All of the other less common benign breast conditions mentioned do not increase the risk of developing breast cancer but may need to be biopsied to confirm what they are. A lipoma is a fatty tumor that can form almost anywhere in the body, including the breast. A hamartoma is a painless lump made up of fatty, gland, and/or fibrous tissues that results from the overgrowth of mature breast cells. A hemangioma is a rare benign tumor made up of blood vessels. A hematoma is a collection of blood which can occur in the breast as a result of internal bleeding. An adenomyoepithelioma is a rare benign tumor formed by cells in the walls of milk ducts. A neurofibroma is a benign tumor resulting from the overgrowth of nerve cells.[13]

 [MB1]Link to ‘symptoms of breast cancer’ article

 [MB2]Link to ‘how cancer is diagnosed’ article

 [MB3]Link to ‘breast biopsy’ article

References

1.     Non-cancerous Breast Conditions https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions.html (accessed Jun 22, 2021).

2.     Fibrosis and Simple Cysts in the Breast https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions/fibrosis-and-simple-cysts-in-the-breast.html (accessed Jun 22, 2021).

3.     Fat Necrosis and Oil Cysts in the Breast https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions/fat-necrosis-and-oil-cysts-in-the-breast.html (accessed Jun 22, 2021).

4.     Lobular Carcinoma in Situ (LCIS) https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions/lobular-carcinoma-in-situ.html (accessed Jun 22, 2021).

5.     Hyperplasia of the Breast (Ductal or Lobular) https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions/hyperplasia-of-the-breast-ductal-or-lobular.html (accessed Jun 22, 2021).

6.     Adenosis of the Breast https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions/adenosis-of-the-breast.html (accessed Jun 22, 2021).

7.     Fibroadenomas of the Breast https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions/fibroadenomas-of-the-breast.html (accessed Jun 22, 2021).

8.     Intraductal Papillomas of the Breast https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions/intraductal-papillomas.html (accessed Jun 22, 2021).

9.     Granular Cell Tumors of the Breast https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions/granular-cell-tumors-of-the-breast.html (accessed Jun 22, 2021).

10.  Mastitis https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions/mastitis.html (accessed Jun 22, 2021).

11.  Duct Ectasia https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions/duct-ectasia.html (accessed Jun 22, 2021).

12.  Phyllodes Tumors of the Breast https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions/phyllodes-tumors-of-the-breast.html (accessed Jun 22, 2021).

13.  Other Non-cancerous Breast Conditions https://www.cancer.org/cancer/breast-cancer/non-cancerous-breast-conditions/other-non-cancerous-breast-conditions.html (accessed Jun 22, 2021).

14.  Khetrapal, A. Radial Scar Diagnosis and Management https://www.news-medical.net/health/Radial-Scar-Diagnosis-and-Management.aspx#:~:text=Radial%20scars%20%28RS%29%20are%20benign%2C%20tumor-like%20lesions%20which,they%20are%20referred%20to%20as%20complex%20sclerosing%20lesions. (accessed Jun 22, 2021).