This biplasia can be arranged in two growth patterns: pericanalicular (stromal proliferation around epithelial structures) and intracanalicular (stromal proliferation compressing the epithelial structures into clefts). These tumors characteristically display hypovascular stroma compared to malignant neoplasms. Furthermore, the epithelial proliferation appears in a single terminal ductal unit and describes duct-like spaces surrounded by a fibroblastic stroma. The basement membrane is intact. Molecular pathology
Up to 66% of fibroadenomas harbor mutations in the exon (exon 2) of the mediator complex subunit 12 (MED12) gene. In particular, these mutations are restricted to the stromal component. Diagnosis
A fibroadenoma is usually diagnosed through clinical examination, ultrasound or mammography, and often a biopsy sample of the lump. Suspicious findings on imaging may result in a person needing a biopsy in order to gain a definitive diagnosis. There are three types of biopsies: Fine-needle aspiration, core-needle biopsy and surgical biopsy. The method of biopsy depends on the appearance, size and location of the breast mass. Treatment
Fibroadenomas can be expected to shrink naturally and so, most are simply monitored. Monitoring fibroadenomas involves regular check-ups to make sure that the breast mass is not growing and is not potentially cancerous. Check-ups involve physical examinations performed every 3–6 months and optional diagnostic imaging performed every 6–12 months for 1–2 years. Generally, surgery is only recommended if the fibroadenoma gets larger or causes increased symptoms. They are removed with a small margin of normal breast tissue if the preoperative clinical investigations are suggestive of the necessity of this procedure.
A connection between fibroadenomas and reproductive hormones has been suggested which may explain why they present themselves during reproductive years, increase in size during pregnancy, and regress post-menopause.Higher intake of fruits and vegetables, higher number of live births, lower use of oral contraceptives and moderate exercise are associated with lower frequency of fibroadenomas. Pathology
Cytology
The diagnostic findings on needle biopsy consist of abundant stromal cells, which appear as bare bipolar nuclei, throughout the aspirate; sheets of fairly uniform-size epithelial cells that are typically arranged in either an antler-like pattern or a honeycomb pattern. These epithelial sheets tend to show typical metachromatic blue on Diff-Quik staining. Foam cells and apocrine cells may also be seen, although these are less diagnostic features. The gallery images below demonstrate these features. Cellular fibroadenoma, also known as juvenile fibroadenoma, is a variant type of fibroadenoma with increased stromal cellularity. Macroscopic
Approximately 90% of fibroadenomas are less than 3 cm in diameter. However, these tumors have the potential to grow reaching a remarkable size, particularly in young individuals. The tumor is round or ovoid, elastic, and nodular, and has a smooth surface. The cut surface usually appears homogenous and firm, and is grey-white or tan in colour. The pericanalicular type (hard) has a whorly appearance with a complete capsule, while the intracanalicular type (soft) has an incomplete capsule. Microscopic
Fibroadenoma of the breast is a benign tumor composed of a biplastic proliferation of both stromal and epithelial components.