A tumor in the breast represents the most common complaint for which women consult a physician, referring to their change as a mass or a thickening. Approximately 70% of all breast tumors are benign, while fibroadenomas are considered the second most common benign breast lesion with an incidence of 18-20% (following omnipresent fibrocystic changes in the breast).
Fibroadenomas are important as they comprise almost 50% of all breast biopsies (this rate climbs to 75% for biopsies in women younger than 20 years). The expert consensus of opinion is that women with these changes are not at higher risk of developing breast cancer.
Fibroadenomas are usually seen among women who belong to higher socioeconomic classes, but also in dark-skinned individuals. Moreover, the number of full-term pregnancies and body mass index (BMI) were found to negatively correlate with the risk of fibroadenoma development.
On the other hand, the age of menarche and menopause, as well as the usage of hormonal therapy (including oral contraceptive tablets) were shown not to modify the risk of these lesions. Cigarette smoking and vitamin C supplementation are linked to reduced risk of fibroadenomas.
Fibroadenomas are considered hyperplastic lesions that are associated with anomalies in the normal maturation of the breasts, rather than genuine neoplasms. This theory is supported by molecular analysis which has shown that both the epithelial and the stromal cells are polyclonal in these lesions.
There are two main histopathological variants of fibroadenomas: juvenile or cellular fibroadenoma that grows rapidly and is associated with projecting veins and skin ulcerations, and giant fibroadenoma that displays a substantial degree of stromal cellularity and is usually larger than five centimeters in diameter.
Estrogen and progesterone (two primary ovarian hormones) and lactation during pregnancy can successfully stimulate fibroadenomas, whereas in menopause they undergo atrophic remodeling. Some of them bear receptors on their surface and respond to human epidermal growth factor (EGH) and growth hormone.
They are rarely seen in older patients, where they may go through involutional change – either due to increased stromal growth or because of an unrecognized infarction with necrosis. The end-result is calcified or hyalinized fibroadenomas.
In those rare occasions of malignant transformation of fibroadenomas, 50% of such tumors show histopathological characteristics of lobular carcinoma in situ, 20% of infiltrating lobular carcinoma, whereas 20% are ductal carcinoma in situ. The remaining 10% of such malignancies are infiltrating ductal carcinoma.
Fibroadenomas clinically present as solid breast lumps that are usually round and firm with distinct borders, non-tender and easily movable. They are usually between 2 and 3 cm in size, albeit they can be smaller than 1 cm or larger than 10 cm.
Furthermore, these lesions can be solitary or multiple. Between 10 and 16% of patients have multiple fibroadenomas (up to four of them in a single breast), which may be present from the start or discovered over a period of years. Although genetics usually does not play a significant role in fibroadenoma development, most of the patients with multiple lesions exhibit a strong family history.