B3 Lesions at Vacuum-Assisted Breast Biopsy under Ultrasound or Mammography Guidance: A Single-Center Experience on 3634 Consecutive Biopsies

Simple Summary Image-guided biopsy of suspicious findings at mammography or breast ultrasonography can result in the diagnosis of lesions with uncertain malignant potential (B3 lesions). These, in turn, can turn out to be cancer (i.e., they are upgraded) when larger specimens of tissue are examined after breast surgery, especially if these lesions belong to the B3b subcategory, characterized by a higher probability of malignancy than the B3a subcategory. This uncertain nature makes their management highly controversial. We aimed to report a particularly large series of B3 lesions—coming from an internationally certified Breast Unit—since such series are seldom available. In this series of 3634 consecutive biopsies, we found 604 B3 lesions, of which 17 (2.8%) were upgraded to malignancy after surgery. B3b lesions had an almost 12-fold higher upgrade rate (4.7%) than B3a lesions (0.4%), reinforcing the evidence that recommends surgery for B3b lesions and acknowledges the possibility of active surveillance of B3a lesions. Abstract The rate of upgrade to cancer for breast lesions with uncertain malignant potential (B3 lesions) diagnosed at needle biopsy is highly influenced by several factors, but large series are seldom available. We retrospectively assessed the upgrade rates of a consecutive series of B3 lesions diagnosed at ultrasound- or mammography-guided vacuum-assisted biopsy (VAB) at an EUSOMA-certified Breast Unit over a 7-year timeframe. The upgrade rate was defined as the number of ductal carcinoma in situ (DCIS) or invasive cancer at pathology after excision or during follow-up divided by the total number of B3 lesions. All lesions were reviewed by one of four pathologists with a second opinion for discordant assessments of borderline cases. Excision or surveillance were defined by the multidisciplinary tumor board, with 6- and 12-month follow-up. Out of 3634 VABs (63% ultrasound-guided), 604 (17%) yielded a B3 lesion. After excision, 17/604 B3 lesions were finally upgraded to malignancy (2.8%, 95% confidence interval [CI] 1.8–4.5%), 10/17 (59%) being upgraded to DCIS and 7/17 (41%) to invasive carcinoma. No cases were upgraded during follow-up. B3a lesions showed a significantly lower upgrade rate (0.4%, 95% CI 0.1–2.1%) than B3b lesions (4.7%, 95% CI 2.9–7.5%, p = 0.001), that had a 22.0 adjusted odds ratio for upgrade (95% CI 2.1–232.3). No significant difference was found in upgrade rates according to imaging guidance or needle caliper. Surveillance-oriented management can be considered for B3a lesions, while surgical excision should be pursued for B3b lesions.