Breast masses occur frequently, as evidenced by more than 1.3 million excisional biopsies performed on American women yearly.1,2 Approximately 80% of these procedures are for benign lesions, most commonly fibroadenomas.1-4 Although it has been repeatedly stated that one-third to one-half of fibroadenomas will regress within 5 years of diagnosis, the data on the natural history of fibroadenomas varies.5-8 Fibroadenomas may occur at any age, but are most likely to occur in the second and third decades of life and are the most common breast masses in women under 30 years of age.2,9-11 Up to 10% of women will develop a fibroadenoma during their lifetime, and the majority will choose to undergo a procedure to remove the mass.2,4 Fibroadenomas account for 30% to 75% of all breast biopsies, more than 500,000 annually, and 75% of breast biopsies in women younger than 20 years.3,9,10

Fibroadenomas have typical characteristics on physical exam, mammography, and ultrasound.9 On physical exam, a fibroadenoma is a painless, spherical, smooth, and mobile mass (historically termed a “breast mouse” by European surgeons) with highly circumscribed margins, typically 1 to 3 cm in diameter.2,3,9 Ultrasound characteristics are typical of a benign mass and include a smooth, well-defined lesion that is iso- or mildly hypoechoic. It may be surrounded by a thin, echogenic pseudocapsule.12,13 On mammography, fibroadenomas are again seen as smooth round or oval masses that may contain course calcifications; multiple lesions may be noted.12,13 Fibroadenomas may be multiple in up to 15% to 20% of patients, especially dark-skinned individuals.2,10,12 The differential diagnosis for these lesions includes fast-growing juvenile fibroadenoma, phyllodes tumor, and colloid and medullary carcinomas.2 Most lesions require biopsy at some point. Others may be monitored without biopsy if they meet strict criteria, such as those described by Stavros and colleagues.14 Image-guided large-core needle biopsy is the method of choice, as the sample provides better differentiation of benign from malignant masses and fibroadenoma from phyllodes tumor.2

Acceptable management includes observation, excisional biopsy, and newer, minimally invasive alternatives. Adolescents may be safely observed for a period of time after physical exam reveals an apparently benign mass. Older women and those with persisting or enlarging masses should have histologic confirmation.3 Although a period of observation is acceptable for teenage patients, there are several valid reasons to support treating some benign lesions more aggressively. Large lesions may become symptomatic, causing feelings of heaviness, asymmetry, pain, or discomfort.9 Infrequently, benign masses may increase in size during pregnancy or during use of hormonal contraception or other types of hormonal therapy.10 Emotional distress created by the frequent follow-up required when patients attempt nonoperative therapy causes many to choose alternative approaches.1,3,9 In addition, benign masses may impair physical examination and mammographic evaluation due to mass effect.2

For many years, excisional biopsy has been the definitive treatment for all breast lesions. The financial burden placed on the health care system for serial office visits and/or operating suite utilization, as well as the morbidity, cosmetic alteration due to scarring, and patient discomfort caused by surgical excision, have stimulated the search for alternative therapies.2,4,9 Recently, several minimally invasive approaches have been considered, including percutaneous excision and thermal ablation. Thermal ablation includes radiofrequency ablation, microwave therapy, high-intensity focused ultrasound, laser ablation, and cryoablation.3,4 Percutaneous excision may be performed using vacuum-assisted core biopsy devices.9 This technique may be performed in an office setting. The primary limitations of vacuum-assisted percutaneous excisions include incomplete excision and recurrence of tumor. Complete excision of all imaged evidence of a given lesion requires skill and may leave histologic remnants, which can occasionally regrow in younger patients. Approximately 30% of patients have some residual visible abnormality, as is also the case with open excision, especially in patients with larger tumors.9,15 Prior studies have suggested that residual tumor may give rise to recurrence necessitating a second procedure, but there are few long-term follow-up data to support this assumption.2,10

Cryoablation works to achieve tissue necrosis by alternately freezing and thawing the targeted tissue.2,4 Injury is caused by intracellular ice formation, osmotic imbalances, and resultant membrane rupture.2,4 Damage to endothelial cells of the microcirculation causes ischemia, leading to indirect injury of the lesion.2,4

Cryoablation, developed in the late 1990s, is an attractive, minimally invasive therapy for many patients. Experience with this technique reveals that it is a cost-effective approach. Because cold acts as a natural anesthetic, it requires only local anesthesia for probe insertion, can be performed in an office setting without sedation, and is a relatively simple procedure.2,4 It has low morbidity and cosmetic benefits compared with surgical excision, as it does not require tissue removal and leaves minimal skin scarring.10 To minimize unnecessary concern and disappointment, patients and their treating physicians, including breast imagers, must be properly counseled and educated regarding the expected parenchymal changes that may be detected on physical and radiologic exams for 12 to 36 months after the procedure.

Masses suitable for cryoablative therapy include those detected by physical exam and, in certain patients, by imaging and biopsy consistent with a fibroadenoma.3 The mass must be visible by ultrasound. Before performing cryoablation, it is necessary to obtain adequate tissue for histologic diagnosis, as biopsy interpretation cannot be performed after this procedure due to coagulation necrosis in the lesion.3

The primary limitation of cryoablation is a persistent palpable mass or scar created by the intended tissue injury associated with the procedure. Patients undergoing cryoablation, including those with nonpalpable masses before the procedure, must be willing to accept the development of a temporarily (12 to 36 months) palpable mass after the procedure.10 Several studies have provided the following results: 50% will have a palpable mass at 6 months, up to 35% will have a palpable mass after 12 months, and 16% will still have a palpable mass at an average of 2.6 years of follow-up.2,5,10 Larger lesions have a greater likelihood of remaining palpable for a longer period of time or indefinitely.2,10