Fibroadenoma

Fibroadenoma is the most common breast neoplasm, occurring in all age groups, but especially common in young women from 20 to 35 years of age. In contrast with the ill-defined nature of fibrocystic change, fibroadenoma are movable, discrete nodules, measuring usually less than 4 cm in maximum dimension. They often increase in size with pregnancy because of lactational changes.

Cytologic diagnostic features

• High cellularity
• Tightly cohesive, flat, honeycomb sheets and tridimensional aggregates
• Fingerlike branching and stag horn-like epithelial clusters
• Numerous bipolar bare nuclei
• Fragments of fibrotic, sometimes fibromixoid stroma
• Apocrine and foamy cells can occasionally be present
• Occasional epithelial atypia

Aspirates from fibrocystic change and fibroadenoma show the same range of cytologic features. However, the clinical findings and the mammographic picture are usually quite different. FNAs of fibroadenoma can be a source for false-positive diagnoses of malignancy, particularly when hypercellular smears show loose epithelial cohesion, which can be an artefact of vigorous smear preparation, and epithelial atypia. The presence of bare nuclei should suggest the benign nature of the lesion, along with the clinical and mammographic picture.