[161] High Grade Lobular Carcinoma In Situ in Breast Excision: Potential for Misdiagnosis as Solid Type DCIS or Classical LCIS

Fadi Habib, Susanna Syriac, Dan Wang, Song Liu, Rouzan Karabakhtsian, Dongfeng Tan, Thaer Khoury. Roswell Park Cancer Institute, Buffalo, NY; University of Kentucky, Lexington, KY; MD Anderson Cancer Center, Houston, TX

Background: Differentiating ductal carcinoma in situ (DCIS) and classical lobular carcinoma in situ (C-LCIS) from high grade lobular carcinoma in situ (HG-LCIS) on excisional biopsy has important clinical implications. The purpose of this study was to determine the frequency of misdiagnosing HG-LCIS as DCIS or C-LCIS, and compare the difference in risk of mammary or non-mammary cancer between HG-LCIS and C-LCIS.
Design: All mammary carcinoma in-situ (MCIS) cases (from 1995 to 2010) reported as solid type DCIS (n=69), HG-LCIS (n=4) and C-LCIS (n=37) were reviewed and reclassified according to WHO classification. LCIS was graded using 2-tier grading system, as classical (grade 1 and 2) or high grade (pleomorphic, signet ring, necrotic, macro-acinar and mixed). E-cadherin immunostain was performed on all cases. The staining was graded from 0+ to 3+. Complete negative staining in addition to lobular carcinoma (LC) morphology was considered for the designation of LCIS phenotype. Equivocal staining (1+) was considered for the designation of undetermined MCIS. Cases with LC cells involving DCIS were designated as mixed MCIS. Key clinicopathological data were abstracted for all LCIS cases. Fisher's exact test was used for statistical analysis.
Results: Pure solid type DCIS was seen in 36 cases. There were a total of 13 HG-LCIS cases, 9 (69.2%) of which were misdiagnosed [3 of 39 (7.7%) reported C-LCIS and 6 of 36 (16.7%) reported pure solid type DCIS]. There were 2 cases of mixed MCIS and 2 undetermined MCIS. The median age of patients with HG-LCIS and C-LCIS was 56 (range 40-80) and 51 (range 42-79) years, respectively. HG-LCIS caries higher risk for non-mammary cancer than C-LCIS [4 of 12 (33.3%) vs. 1 of 32 (3.1%) respectively, p=0.02], while both processes have similar risk for mammary cancer. No statistically significant difference was seen between these groups with relation to menopausal status, race, or family history.
Conclusions: 1) Misdiagnosing HG-LCIS as C-LCIS or DCIS is not uncommon. 2) E-cadherin should be performed on any solid type MCIS to accurately differentiate between LCIS and DCIS. 3) In addition, proper grading for LCIS is important, as the HG type carries higher risk for developing non-mammary cancer compared to the classical type.
Category: Breast

Tuesday, March 20, 2012 9:30 AM

Poster Session III # 22, Tuesday Morning


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