Breast fibroadenoma, a benign biphasic tumor, occurs most frequently in women of child-bearing age, especially those under 30 years. Fibroadenoma is usually a slowly growing lesion with size up to 3 cm.1
Most fibroadenomas are present as a single mass, however, the presence of multiple fibroadenomas can be seen in 15% to 20% of the patients.1
Majority of fibroadenomas do not recur after being completely excised, but in adolescent patients, one or multiple new fibroadenomas can occur in areas adjacent to the prior surgical excision site of the same breast or even in the contralateral breast. It has been reported that the average number of masses in cases of multiple fibroadenomas was 3 to 4 in a single breast.2,3
The occurrence of more than five fibroadenomas in an individual patient is much less common. Unlike women with a single fibroadenoma, most of the patients with multiple fibroadenomas have a strong family history of these tumors.2
The etiology of multiple breast fibroadenomas has not yet been clearly established. A possible connection between multiple fibroadenomas and oral contraceptives was proposed but has not been well documented on the literature yet.4
In addition, other possibilities of the pathogenesis may be related to imbalance of in vivo estrogen level, hypersensitivity of local breast tissue to estrogen, dietary factors, or inherited predisposition. Another possible explanation was that the physiologic level of estrogen in such patients did not increase, but instead, the number of estrogen receptor increased.2
The increased sensitivity to estrogen may subsequently lead to mammary gland hyperplasia and even the development of carcinoma. A previous study of a large cohort of women with fibroadenoma revealed that the overall prevalence of atypical epithelial hyperplasia within fibroadenomas was 0.81% and only around 7% of women with atypia developed invasive carcinoma on follow-up.5
An additional large case series of women with fibroadenoma showed carcinoma in situ (ductal and/or lobular) was found in 2% of these patients.6
Therefore, patients with fibroadenoma may have a slightly increased risk of developing breast cancer.
The pathogenesis of formation of the numerous breast fibroadenomas in this patient is unknown. Presumably constant stimulation of estrogen to the breasts and/or increased sensitivity of breast tissue to estrogen during adolescence may cause the fibroadenomas to increase dramatically in size, up to 8 cm, and in quantity to a number of 50, which has not been reported on the literature. Some authors defined fibroadenomas larger than 5 cm as giant fibroadenomas.1
However, this definition is not universally accepted. The postoperative recurrence of fibroadenomas in this patient perhaps was due to the constant presence of the predisposing factors and should not be considered a relapse. Based on microscopic evaluation of this case, there was no evidence of atypical epithelial hyperplasia, carcinoma in situ, or invasive carcinoma in these fibroadenomas.
There is paucity on the literature on multiple fibroadenomas in bilateral breasts and axillary accessory breast. We report this case with an extremely unusual presentation of multiple fibroadenomas in hoping to expand the literature and to provide insight to aetiology of multiple fibroadenoma formation, its natural history, and advice on management.