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Upgrade Rates Following A Core Needle Biopsy Diagnosis Of Lobular Carcinoma In Situ
*Robert M Pride, *Tanya L Hoskin, *Rafael E Jimenez, *Amy C Degnim, Tina J Hieken
Mayo Clinic, Rochester, MN

Objective: Classic lobular carcinoma in situ (LCIS) is a high-risk lesion conferring a substantially elevated risk for future breast cancer, similar in this regard to atypical ductal hyperplasia (ADH). LCIS is uncommon as the sole and highest risk lesion on core needle biopsy (CNB). Because of its rarity and clinical/pathologic overlap with atypical lobular hyperplasia (ALH), patient management following a CNB diagnosis of LCIS remains controversial. While observation is an option for ALH on CNB due to its low upgrade rate (~1%), there is no such consensus for LCIS and very little data on upgrade rates. Thus our aim was to evaluate the upgrade rate to cancer at surgical excisional biopsy. Methods: With IRB approval, we identified 56 patients from our prospective database (10/2008-8/2019) with LCIS on CNB as their highest risk lesion who had surgical excisional biopsy. We excluded patients with concurrent ipsilateral invasive cancer, DCIS or pleomorphic LCIS. We defined upgrade as invasive cancer or DCIS. Confidence intervals were calculated using the Wilson score method. Factors associated with upgrade to cancer were assessed using chi-square and Wilcoxon rank-sum tests. Results: On final surgical pathology, 6 of 56 patients (10.7%, 95% CI: 5.0-21.5%) with classic LCIS on CNB as their highest risk lesion were upgraded to cancer: invasive lobular cancer (n=5) and DCIS (n=1). Median patient age was 54 years. The indication for CNB was mammographic calcifications in 30 (53.6%), mass/distortion in 17 (30.3%), non-mass enhancement in 7 (12.5%), and MRI/ultrasound discordance in 2 (3.6%). Eight patients (14.3%) had concurrent contralateral breast cancer (6 invasive, 2 DCIS) and 7 (12.5%) prior ipsilateral (n=2) or contralateral (n=5) breast cancer. While no variables reached statistical significance, upgrade rates were higher among older patients (median age 62 vs 53 years, p=0.10) and those with concurrent contralateral breast cancer (2/8 (25%) vs 4/48 (8.3%), p=0.20). Conclusion: All invasive cancer upgrades were to invasive lobular carcinoma which is notoriously challenging to detect at an early stage. Our data suggest that, similar to the current management of ADH, classic LCIS on CNB should be excised as it confers a substantial risk of upgrade.


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