Winning Abstracts from the 2012 Medical Student Abstract Competition: The Negative Predictive Value of Sonographically-Guided 14-Gauge Core Needle Biopsy of Breast Masses
Author: Charlie Zhang, University of British Columbia, Faculty of Medicine, Class of 2013
Introduction: Percutaneous image-guided core needle biopsy (CNB) is currently the standard of care for the initial diagnosis of suspicious breast lesions. It is less invasive, less time-consuming and less expensive than surgical excision, and causes minimal to no scarring. We aim to determine the negative predictive value (NPV) of sonographically-guided 14-gauge core needle biopsy of breast masses, with detailed analysis of any false negative cases.
Methods: All patients who have had benign pathologic findings on sonographically-guided 14-gauge core needle biopsy of breast lesions from March 2005 through April 2011 at the Vancouver Breast Center were reviewed. Sonographically-guided CNBs were performed using a free-hand technique and a high-resolution ultrasound unit with 10- or 12- MHz linear array transducers. An automated biopsy gun and 14-gauge needles with a 22mm needle throw were used. Core biopsies were fixed in formalin and processed according to standard protocol. 'Strict' true negative cases were defined as lesions which had benign pathology on core biopsy and had either benign pathology upon surgical excision or at least 2 years of stable imaging and/or clinical follow-up. False negative cases were defined as lesions which had benign pathology on core biopsy but malignant histology upon surgical excision. A benign CNB lesion subsequently confirmed to be malignant was considered an "applied true negative" if it was immediately referred to surgery due to suspicious imaging findings. In other words, the false negative histology did not result in delayed diagnosis. The definition of 'applied' NPV was introduced to acknowledge that in actual practice, the imaging findings are considered along with the histology to inform follow-up recommendations.
Results: Of the 339 ultrasonographically visible breast lesions in 319 patients, 117 were confirmed to be benign via surgical excision, and 220 were stable on = 2 years of imaging or clinical follow-up (mean follow-up time 33.1 months, range 24-64 months). The 'strict' NPV of sonographically-guided 14-gauge CNB was determined to be 99.4% (337 of 339 cases), while the 'applied' NPV was determined to be 100%. There were 2 (0.6%) false negative US-guided 14-gauge CNB cases. In both cases of invasive carcinomas, the radiologist determined that there was discordance between imaging and core biopsy pathology, and recommended surgical excision despite the benign core biopsy pathology.
Conclusion: Sonographically-guided 14-gauge core needle biopsy provides a high NPV in assessing breast lesions. Radiologic/pathologic correlations should be performed to avoid delay in the diagnosis of carcinoma.