Background: Management of patients with classic lobular carcinoma in situ diagnosed on core needle biopsy remains controversial, in part because of clinicopathologic overlap with atypical lobular hyperplasia. Although atypical lobular hyperplasia on core needle biopsy is observed because of its low upgrade rate (~1%), consensus is lacking for lobular carcinoma in situ. Therefore, we evaluated lobular carcinoma in situ upgrade rates. Methods: With institutional review board approval, we identified 90 patients (from October 2008 to December 2019) with lobular carcinoma in situ on core needle biopsy as their highest-risk lesion. We excluded patients with concurrent ipsilateral cancer. Variables associated with upgrade were assessed with logistic regression. Results: Of the 90 patients, 81 (90%), median age 55 y, underwent surgical excision. Indications for diagnostic core needle biopsy included mammographic calcifications (48, 53.3%), mass/distortion (28, 31.1%), and non-mass enhancement (12, 13.3%). Final surgical pathology upgraded 11 of 81 patients (13.6%, 95% CI: 7.8%–22.7%) to cancer: invasive lobular (n = 7), invasive ductal (n = 1), and ductal carcinoma in situ/pleomorphic lobular carcinoma in situ (n = 3). Only 1 patient with invasive cancer was node-positive. Concurrent contralateral cancer (OR 4.41, 95% CI: 1.06–17.38, P = .04) and larger lesion size (OR 1.78 per 1 cm, 95% CI: 1.19–2.95, P = .005) predicted upgrade. Conclusion: Our data suggest that, unlike atypical lobular hyperplasia, lobular carcinoma in situ identified on core needle biopsy should be surgically excised. The high proportion of upgrades to early stage invasive lobular carcinoma underscores the value of this approach.
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