Background: A diagnosis of non-classic lobular carcinoma in situ (NC-LCIS) encompasses a variety of lesions with poorly characterized natural history. We evaluated upgrade rates and factors associated with upgrade to malignancy following a core biopsy diagnosis of NC-LCIS, and its natural history.
Methods: Upon Institutional Review Board approval, pathology databases were searched for NC-LCIS core biopsy diagnoses (carcinoma in situ [CIS], CIS with ductal and lobular features [CIS/DLF], pleomorphic LCIS [P-LCIS], variant LCIS [V-LCIS], LCIS with necrosis). Cases with available core and excision pathology were included, while cases with concurrent ipsilateral invasive carcinoma (IC), ductal carcinoma in situ (DCIS), and/or atypical ductal hyperplasia were excluded.
Results: Overall, 121 NC-LCIS cases were identified from 1998 to 2017. We excluded 46 cases with concurrent cancer; 75 patients with 76 NC-LCIS core biopsy diagnoses followed by excision formed our study cohort. Median age was 56 years (range 41-83), and all imaging findings were classified as Breast Imaging Reporting and Data System 4; calcifications were the most common biopsy indication (80%). Excision yielded malignancy in 27 (36%) patients (IC 17, 63%; DCIS alone 10, 37%). We were unable to identify radiologic or pathologic features predictive of upgrade. Of 49 pure NC-LCIS cases, 15 (31%) had mastectomy, 9 (18%) had excision and radiation, and 25 (51%) had excision alone. At a median follow-up of 58 months (range 1-224), 1/25 (4%) patients with excision alone developed ipsilateral DCIS 14 months later.
Conclusions: In this series of NC-LCIS, 36% of cases were upgraded, supporting routine excision. We were unable to identify predictors of upgrade. Among 25 patients with pure NC-LCIS, only one patient developed a future ipsilateral cancer. Further study of the natural history of NC-LCIS is warranted.