Risk of Lobular Neoplasia Upgrade with Synchronous Carcinoma

Atypical lobular hyperplasia (ALH) and classic lobular carcinoma in situ encompass a spectrum of proliferative lesions known as lobular neoplasia (LN). When imaging-concordant and found in isolation on core needle biopsy (CNB), LN infrequently upgrades to carcinoma on surgical excision, and routine excision is not indicated. Upgrade rates in the setting of synchronous carcinoma are not well studied.

Patients with radiology-pathology concordant synchronous LN and separately biopsied ipsilateral (n = 35) or contralateral (n = 15) carcinoma who underwent excision between 2010 and 2021 were retrospectively identified. Frequency of upgrade, to either invasive or in situ carcinoma, was quantified, and factors associated with upgrade were assessed using Fisher's exact test.

The median age was 55 (range 33-74) years. The upgrade rate of LN was 6% and not significantly different between ipsilateral (2.9%) and contralateral (13.3%) carcinoma (p = 0.15). All upgraded LN lesions were ALH on CNB and detected as non-mass enhancement on magnetic resonance imaging (MRI). No additional disease was demonstrated after excision at the site of the original LN CNB in 22.9% (8 out of 35) of ipsilateral and 13.3% (2 out of 15) of contralateral patients. Upgrade was not associated with family history, menopausal status, imaging modality used to detect LN, or extent of LN on CNB (p > 0.05).

Our results demonstrate a low upgrade rate (6%) in our study cohort of LN with synchronous ipsilateral or contralateral carcinoma, which suggests that not all LN mandates excision with synchronous carcinoma. Larger, multi-institution studies are needed to validate these findings.