The definitive diagnosis of fibroadenoma is confirmed by an ultrasound guided biopsy. This is usually done if patients presents with a rapidly enlarging mass, mass >3 cm in size and some other features.

• The definitive diagnosis of fibroadenoma is confirmed by an ultrasound guided biopsy.
• In combination with clinical diagnosis of fibroadenoma, fine needle aspiration (FNA) can improve the sensitivity of the diagnosis to 86%, with a specificity of 76%.^[1]
• Aspiration cytology may confuse fibroadenomas with other benign breast lesions, false diagnosis of a malignant process is uncommon.^[1]
• Indications for an ultrasound guided biopsy include:^[2]

• Rapidly enlarging mass
• Atypical findings on ultrasound such as non-circumscribed margins, complex solid and cystic components, posterior acoustic shadowing
• Lesion greater than 3 cm in size, with no previous studies for comparison
• Patients preference
• History of a risk factor for malignancy regardless of the lesion having a benign appearance on ultrasonography. Examples include a prior chest irradiation, known concurrent cancer not involving the breast, family history of breast cancer.

• The characteristic cytologic features of fibroadenomas include:^[1]

• Clusters of spindle cells without inflammatory or fat cells. This is found in 96% of all fibroadenomas.
• Aggregates of cells with a papillary configuration resembling elk antler (antler horn clusters). Found in about 93%.
• Uniform cells with well-defined cytoplasm lying in rows and columns (honeycomb sheets). Found in about 95%

• A “triple assessment approach” refers to the combination of clinical breast examination, imaging and percutaneous tissue study. This approach allows a 95% accurate differentiation between a benign and malignant lesion.^[3]