Fibroadenomas have previously been regarded as benign neoplasms, but should now be considered as an aberration of normal development. The peak incidence occurs in the third decade. An increasing number of newly developed fibroademonas are being detected in the fifth and sixth decade, probably related to increased use of HRT and mammographic screening.

Fibroadenomas develop from a lobule in the breast rather than from a single cell, and demonstrate high levels of estrogen and sulfates as well as of enzymes responsible for the formation of estrogen (sulfatase and aromatase), suggesting hormone dependency.  Clonal analysis has demonstrated that fibroadenomas are polyclonal lesions.  The natural history of fibroadenomas is now better understood, with 72% resolving over a period of 7 years.

There is no increased risk of breast cancer in patients with fibroadenomas, apart from a small pathological subgroup (i.e., those with complex fibroadenomas - cysts greater than 3 mm in diameter, sclerosing adenosis, epithelial calcifications or papillary change; relative risk [RR] of 3.1 for breast cancer).  Fibroadenomas can undergo vascular infarction during pregnancy and lactation and in their later stages can undergo calcification.

Multiple Fibroadenomas
In a small percentage of patients, multiple fibroadenomas are detected either by clinical examination or screening mammography. The sensible approach in these patients is to investigate each lesion on its merit and perform core biopsies to confirm their benign nature. Excision biopsy is advised for any lesion where the diagnosis is uncertain.

Juvenile and Giant Fibroadenomas
Classically, juvenile fibroadenomas are rare and occur in adolescence. They are characterized by a rapidly growing lesion that usually attains a size greater than 5 cm in diameter causing distortion and asymmetry of the breast. These lesions require surgical excision for cosmetic reasons. Giant fibroadenomas attain a similar size but are usually found in the breasts of pregnant or lactating women and increase under the hormonal environment of these physiological conditions. They frequently diminish in size after the hormonal influences recede. If they remain large, they may be excised for cosmetic reasons. Neither of these lesions have any malignant potential.

Patients present with a discrete lump that may in rare cases be associated with tenderness. Occasionally patients may present with multiple discrete lumps at initial presentation.

Clinical examination usually demonstrates a well-circumscribed, mobile, firm, discrete breast lump.

All clinical fibroadenomas should be investigated by mammography with or without ultrasound and FNAB or core biopsy.

Fibroadenomas usually appear as oval or round soft-tissue densities with smooth or lobulated margins. They usually have very well-defined borders and may exhibit the “halo” sign, in which a thin dark border is seen around the edge of the mass. Densities with these features are highly likely to be benign in origin. It is only when the typical coarse “popcorn-like” calcification is seen in association with the soft-tissue mass that the appearance is pathognomonic of a fibroadenoma. When multiple fibroadenomas are present, there is usually a mixture of soft-tissue masses with either absent or varying degrees of calcification.

As the majority of fibroadenomas present as breast lumps in younger women ultrasound is frequently our first-line of investigation. The typical appearance of a fibroadenoma is that of an oval-shaped, well-defined nodule with a uniform internal echo pattern. Deep to the lesion there is no alteration in the echo texture nor is there enhancement (“bright up”).

The well-defined borders of a fibroadenoma are frequently illustrated by thin acoustic shadows seen at the edge of the lesion. Variation on such appearances is fairly common. The nodule may appear lobulated or have varying internal echo textures and in rare cases fibroadenoma may cast an acoustic shadow.

Even when presenting with the typical clinical and ultrasound features of a fibroadenoma, the diagnosis should be confirmed by needle biopsy.

Macroscopic Appearance
Fibroadenomas are characteristically well-circumscribed round or ovoid masses that are clearly demarcated from the surrounding breast tissue. The texture of the cut surface varies from soft, myxoid through firm, rubbery to very firm depending on the age of the lesion. They have a white or yellow color and a lobulated appearance. Ductal clefts are sometimes apparent.

Microscopic Appearance
As the name implies, there are both stromal and glandular components in fibroadenomas. The stromal component is usually uniformly loose, cellular and intimately related with the epithelium-lined ductal structures that comprise the glandular element. In older lesions, the stroma becomes less cellular and may become densely hyalinised. Calcification of the hyalinised stroma may also occur. The ductal structures are lined by an epithelium, which usually shows mild usual-type hyperplasia.

Fibroadenomas have traditionally been divided into pericanalicular and intracanalicular types based on the degree of stromal herniation into the ductal structures. This distinction, however, has no clinical relevance, and both patterns are often present in a single lesion. Tubular adenoma is best regarded as a variant of fibroadenoma that has a minimal stromal component and a tubular glandular component lined by regular ductal epithelium.

Since fibroadenomas arise from the breast lobule, all changes that occur in the lobule may also be seen in a fibroadenoma namely apocrine metaplasia, sclerosing adenosis and lactational changes. The latter is particularly common in the tubular adenoma variants.

Given the natural history of the disease, and provided triple assessment has demonstrated unequivocally that the lesion in question is a fibroadenoma, our policy is not to recommend excision of these lesions. Some authors recommend excision of all fibroadenomas greater than 3 cm in diameter.

The only rationale for adopting such a policy is if fibroadenomas increase in size and there is concern that a delay in surgical excision might result in a greater amount of breast tissue requiring excision, thereby potentially resulting in poorer breast cosmesis. Similarly, in treating these lesions conservatively, we do not adopt a cut-off point as far as age is concerned.

There is no scientific basis in recommending surgical excision over the age of 40 years. Despite adequate reassurance following an unequivocal diagnosis based on triple assessment, an occasional patient will request excision based on a deep-seated fear of cancer. In this exceptional circumstance, it would be reasonable to proceed to surgical excision.

A.D. Purushotham, P. Britton and L. Bobrow
A prospective study of benign breast disease and the risk of breast cancer. JAMA 2002


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