Incidental Breast Masses on Ultrasound: What are Their Characteristics and Clinical Outcome?

Abstract

Objective: To evaluate the characteristics and clinical outcome of non-palpable breast lesions screened by ultrasound. Methods: From January 2011 to June 2011, all new cases referred to the breast clinic at Tuen Mun Hospital, Hong Kong, were identified. All patients underwent ultrasound with or without mammography. Patients with a palpable or mammographically detected breast mass were included in the control group. Patients with nonpalpable breast lesions detected incidentally on ultrasound only were included in the investigation group. Any patients who underwent targeted ultrasound were excluded. Baseline patient demographics, including age and family history of breast cancer, were documented. Lesion characteristics on ultrasound, including maximum dimension and Breast Imaging Reporting and Data System (BI-RADS) classification, were analysed. The nature of the lesions was confirmed histologically or by follow-up imaging for at least 2 years to indicate benignity. Results: A total of 196 patients with 422 lesions were identified. Among the 422 lesions, 130 were palpable or mammographically detected lesions (control group) and 292 were non-palpable ultrasound-detected lesions (investigation group). The baseline characteristics in both groups were comparable. The mean age was 44 years in the control group and 42 years in the investigation group. There were 10 and 8 patients with a family history of breast cancer in the control group and investigation group, respectively. Compared with the control group, the maximum dimension of the lesion was significantly smaller in the investigation group (p < 0.05). The BI-RADS classification was significantly lower in the investigation group (p < 0.05). A total of 156 lesions had tissue diagnosis and 270 lesions were followed up for at least 2 years with no change or a decrease in size, indicating benignity. In the control group, 18 (13.8%) lesions were malignant while in the investigation group, no lesions were malignant (p < 0.05). Conclusion: Ultrasound can detect small lesions that are mammographically occult and non-palpable. However, these lesions are likely more benign-looking (BI-RADS 2/3) and pathologically benign.