[175] Pleomorphic Lobular Carcinoma In Situ on Breast Core Biopsies: An Under-Diagnosed Entity, Clinical Significance, and Immunoprofile.

Yaser Hussein, Sudeshna Bandyopadhyay, Bassam Albashiti, Quratulain Ahmed, Sumit Yadam, Lamia Fathallah, Amro Almradi, Haitham Arabi, Rouba Ali-Fehmi. Wayne State University, Detroit, MI; St John Hospital and Medical Center, Detroit, MI

Background: Pleomorphic lobular carcinoma in situ (PLCIS) is a recently characterized entity that shares morphologic features with solid ductal carcinoma in situ (DCIS) which may lead to misclassification. The objective of this study is to determine the frequency of misinterpreted PLCIS cases as solid DCIS from our pathology archives and to evaluate the clinico-pathologic and immunohistochemical (IHC) features of the re-classified PLCIS cases.
Design: 100 consecutive breast core biopsies over a period of 10 years, originally diagnosed as solid DCIS (intermediate/high grade) without invasion, were identified from our database for E-cadherin staining. Re-classification of solid DCIS into PLCIS was based on E-Cadherin negativity and morphology. The re-classified cases were matched with 12 consecutive cases of classic lobular carcinoma in situ (C-LCIS) that were also retrieved from our database. A panel of IHC stains included ER, PR, P53, and Ki-67 was done to compare the immunoprofile characteristics of the PLCIS with C-LCIS. The subsequent resection specimens were reviewed.
Results: Among 100 cases of solid DCIS, 6 (6%) cases were revised as PLCIS. E-cadherin was negative in all the 6 cases. Resection specimen revealed invasive lobular carcinoma as well as LCIS and DCIS in 2 cases, DCIS in 2 cases, and LCIS in 1 case. Compared to C-LCIS, PLCIS showed higher expression of P53 (66% vs 8%, p=0.02). No significant difference was seen in ER expression (100% vs 92%) and PR expression (50% vs 67%) between the 2 groups. Moderate to high proliferation index with Ki-67 staining was observed in 4 out of 6 PLCIS cases (66.7%) compared to 1 out of 12 of C-LCIS (8%)(p=0.02).
Conclusions: Our study shows that PLCIS is an under-recognized entity in breast core biopsies and can show aggressive features such as high proliferation rate and p53 mutation. Although the current recommendation is to treat them similar to DCIS, further investigation with larger number of cases and long term outcome is warranted.
Category: Breast

Tuesday, March 1, 2011 1:15 PM

Platform Session: Section B, Tuesday Afternoon


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