A 23-year-old woman seeks medical advice after discovering a painless lump in her right breast during a self-examination. Her medical and surgical histories are unremarkable, and there is no history of breast trauma. The patient is nulliparous; she attained menarche at the age of 13, and her menstrual cycles are regular. Her family history is negative for breast malignancies.
The scan reveals a well-circumscribed, oval, solid mass in the upper outer quadrant measuring 1.7x2.2 cm, with a sharp, smooth contour and uniform hypoechogenicity.
The mammogram shows a well-circumscribed, ovoid mass in the upper outer quadrant measuring 1.7x2.2 cm, hypodense to the glandular tissue.
Fine-needle aspiration cytology (FNAC) reveals abundant, bare, bipolar stromal nuclei surrounding sheets of metachromatic epithelial cells, arranged in an antler-like pattern.
The biopsy shows hyperplasia of both the epithelial and stromal components, with a proliferation of the intralobular stroma compressing the epithelium (peri-canalicular pattern); there is no cytological atypia, and the basement membrane is intact.