Background. Lobular neoplasia (LN) includes atypical lobular hyperplasia (ALH) and lobular carcinoma in situ (LCIS). LN often is an incidental finding on breast core needle biopsy (CNBx) and management remains controversial. Our objective was to define the incidence of malignancy in women diagnosed with pure LN on CNBx, and identify a subset of patients that may be observed. Methods. Patients diagnosed with LN on CNB between January 1993 and December 2010 were identified. Patients with an associated high-risk lesion or ipsilateralmalignancy at time of diagnosis were excluded. All cases were reviewed by dedicated breast pathologists and breast imagers for pathologic classification and radiologic concordance, respectively. Results. The study cohort was comprised of 184 (1.3 %) cases of pure LN (147 ALH, 37 LCIS) from 180 patients. Pathologic-radiologic concordance was achieved in 171 (93 %) cases. Excision was performed in 101 (55 %) cases and 83 (45 %) were observed. Mean follow-up was 50.3 (range, 6-212) months. Of cases excised, 1 of 81 (1.2 %) ALH and 1 of 20 (5 %) LCIS cases were upstaged to ductal carcinoma in situ (DCIS) and invasive lobular carcinoma (ILC), respectively. Only 1 of 101 (1 %) concordant lesions was upstaged on excision. Of the cases observed, 4 of 65 (6.2 %) developed ipsilateral cancer during followup: 1 of 51 (2 %) case of ALH and 3 of 14 (21.4 %) cases with LCIS (2 ILC, 2 DCIS). During follow-up, 2.9 % (4/ 138) patients with excised or observed LN developed a contralateral cancer. Conclusions. These data support that not all patients with LN diagnosed on CNB require surgical excision. Patients with pure ALH, demonstrating radiologic-pathologic concordance, may be safely observed.
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