Patients often present to plastic surgeons with breast asymmetry of unknown etiology. Many patients are females in late adolescence and present complaining of a hypoplastic breast on the smaller side. However, full evaluation may reveal that the larger breast contains the abnormality. Fibroadenomas typically present as firm, mobile, painless, easily palpable breast nodules. However, giant fibroadenomas can present as unilateral macromastia without definable borders or texture differences. Diagnosis is essential since fibroadenomas tend to persist and grow. However, physical examination and standard radiographic evaluations (mammograms and ultrasounds) fail to clarify the diagnosis in many cases. Magnetic resonance imaging (MRI) has improved preoperative diagnosis, but tissue diagnosis is frequently necessary and resection of giant fibroadenomas is essential as they enlarge to the point of causing psychological detriment or mass effects, including venous congestion, glandular distortion, pressure necrosis, and occasionally ulceration. In this article we review nine patients presenting with unilateral macromastia to a tertiary breast care center with a review of the pertinent literature. The differential diagnosis, evaluation modalities, and treatment options of breast asymmetry and unilateral breast masses are presented. Postexcision breast reconstruction is discussed.