Introduction: Flat epithelial atypia (FEA), classical lobular neoplasia (LN), papillary lesions (PL), radial scars (RS) and atypical ductal hyperplasia (ADH) are lesions of uncertain malignant potential in the breast, which are described as B3 lesions in the B classification system of the European Working Group for Breast Cancer Screening Pathology. Current standard for management of B3 lesions on core needle biopsy (CNB) or vacuum assisted biopsy (VAB), is wide local excision (WE). However, recent consensus-based guidelines no longer recommend WE for all such lesions, but propose surveillance following CNB or VAB to be sufficient in some cases. In the absence of a Belgian guideline on the treatment of B3 lesions, this study was conducted to identify which B3 lesions have the lowest likelihood for breast malignancy and could therefore be spared from WE.

Methods: Using data from the Belgian Cancer Registry (BCR), all patients with a new diagnosis of a B3 lesion on CNB or VAB between 2013-2016 and who had a histological follow up with VAB or WE after CNB or WE after VAB were included. Histological follow-up was retrieved from BCR and limited to 12 months following diagnosis. Histology was compared between the first- and follow-up investigation to determine the upgrade risk to ductal carcinoma in situ (DCIS) or invasive breast cancer (IC) according to the type of B3 lesion. Patients with synchronous (pre-) invasive lesions were excluded.

Results: Between 2013-2016 there were 812 B3 lesions available for upgrade analysis after initial diagnosis. After CNB 551 lesions had WE or VAB as follow up and after VAB 261 lesions had WE. After primary diagnosis on CNB, the total upgrade risk was 19,0%. There was histological agreement in 57,9% and no B3 lesion or upgrade was reported in 21,8%. Per B3 lesion subtype the upgrade risk to DCIS - IC after diagnosis on CNB was: ADH 17,1%-12,4%, FEA 21,1% - 18,4%, LN 18,9% -21,6%, RS 14,3% - 11,4%, and PL 7,2% - 3,2%. After initial diagnosis on VAB the total upgrade risk was 14,9%. There was histological agreement in 52,9% and no B3 lesion or upgrade was found in 31,4%. Per B3 subtype the upgrade risk to DCIS - IC after diagnosis on VAB was: ADH 17,3%- 2,7%, FEA 11,7%- 5,9%, LN 0,0% - 4,3%, PL 10,4% - 2,1%. We found no upgrade for RS. (Table 1).

Conclusions:

In a series of B3 lesions with a histological follow-up, we notice that overall upgrade risk is higher for lesions detected on CNB than on VAB: 19,0% vs. 14,9%. The majority of lesions showed histological agreement between initial B3 diagnosis and histological follow-up: 57,9% after CNB and 53,5% after VAB. More investigation is needed to make a proper risk assessment as to which B3 lesions can be followed with regular surveillance. Also, further prospective research is needed to get a better understanding of associated risk factors for upgrade, upgrade risk and lifetime risk of developing breast cancer after diagnosis of a B3 lesion.

Table 1: Upgrade risk per B3 subtype after diagnosis on CNB or VAB

SubtypeNumberCNB followed by VAB or WEDCISICTotal Upgrade riskCNBNumberVAB followed by WEDCISICUpgrade riskVAB followed by WE
ADH 105 17,1% 12,4% 29,5% 110 17,3% 2,7% 20,0% 
FEA 38 21,1% 18,4% 39,5% 51 11,7% 5,9% 17,6% 
LN 37 18,9% 21,6% 40,5% 46 0% 4,3% 4,3% 
PL 336 7,2% 3,2% 10,4% 48 10,4% 2,1% 12,5% 
RS 35 14,3% 11,4% 25,7% 0% 0% 0% 
Total 551  261   
Upgrade 105/55119,0%  39/26114,9%   
B3 lesion 319/55157,9%  138/26152,9%   
No B3 lesion 120/55121,8%  82/26131,4%   
Result not available 7/5511,3%  2/2610,8%   
SubtypeNumberCNB followed by VAB or WEDCISICTotal Upgrade riskCNBNumberVAB followed by WEDCISICUpgrade riskVAB followed by WE
ADH 105 17,1% 12,4% 29,5% 110 17,3% 2,7% 20,0% 
FEA 38 21,1% 18,4% 39,5% 51 11,7% 5,9% 17,6% 
LN 37 18,9% 21,6% 40,5% 46 0% 4,3% 4,3% 
PL 336 7,2% 3,2% 10,4% 48 10,4% 2,1% 12,5% 
RS 35 14,3% 11,4% 25,7% 0% 0% 0% 
Total 551  261   
Upgrade 105/55119,0%  39/26114,9%   
B3 lesion 319/55157,9%  138/26152,9%   
No B3 lesion 120/55121,8%  82/26131,4%   
Result not available 7/5511,3%  2/2610,8%   

Citation Format: Nynke Willers, Patrick Neven, Giuseppe Floris, Cecile Colpaert, Eva Oldenburger, Sileny Han, Chantal Van Ongeval, Ann Smeets, Francois Duhoux, Hans Wildiers, Petra Denolf, Isabel De Brabander, Nancy Van Damme, Harlinde De Schutter. The upgrade risk to (pre-)invasive breast cancer for B3 lesions diagnosed on core needle or vacuum assisted biopsy. A Belgian retrospective study [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS7-52.