[267] Invasive Ductal Carcinoma with Lobular Features and Invasive Pleomorphic Lobular Carcinoma Are They Different Entities?

G Omeroglu, WM Hanna, S Nofech-Mozes. Sunnybrook Health Sciences Centre, Toronto, Canada

Background: Recent data suggest that the prognosis of ductal and lobular carcinoma is comparable when adjusted for tumor grade and stage; however, lobular carcinoma has perceived biologic characteristics that can affect the diagnostic approach and management. E-cadherin is helpful in differentiating invasive ductal carcinoma with lobular features (IDC-LF) from invasive pleomorphic lobular carcinoma (PLC) as they have overlapping growth pattern. We compared clinical and histopathologic characteristics and the expression of biological markers in IDC-LF and PLC.
Design: We identified 97 cases from the pathology database using natural language search for lobular within breast specimens. Histopathologic features and ER, PR, Her-2/neu and E-cadherin status were studied. Cases were classified as IDC-LF when E-cadherin was expressed as complete membranous stain or PLC when E-cadherin was negative.
Results: Based on E-cadherin expression, there were 51 IDC-LF and 46 PLC cases. The mean age was significantly higher in PLC (55.9 vs. 63.3, p=0.0047). The rate of screen detected cancer was slightly higher in PLC (41% vs. 54.3% p= 0.197). The type of in situ component was significantly associated with that of the invasive component (DCIS present in 64% of IDC-LF vs.0% of PLC; p<0.001 and LCIS present in 58.7% of PLC vs.7.8% of IDC-LF; p<0.001). Tumor size, nodal status, lymphovascular invasion bilaterality and multifocality were comparable between the groups (p=0.749, p=0.453, p=0.052 p=0.879 and p=0.321 respectively). Interestingly, the likelihood of ER, PR expression was not significantly different (ER+ in 90.2% of IDC-LF vs.91.3% of PLC; p=0.852; PR+ in 72.5% of IDC-LF vs.73.4% of PLC; p=0.880). Her-2/neu overexpression was demonstrated in 15.72% of IDC-LF vs. 4.3% of PLC. The lower proportion of Her2/neu overexpression in PLC approached significance (p=0.068). The likelihood of mastectomy was slightly higher in PLC (43.5% vs. 37.2%, p=0.535). With a mean follow up of 24 months (both groups), there were 3/51 locoregional recurrences and one distant recurrence (liver) in IDC-LF cases and 3/46 locoregional recurrences and one distant recurrence (bone) in PLC cases.
Conclusions: Unlike the known differences between classic lobular and ductal carcinomas, PLC does not significantly differ from IDC-LF in its biological characteristics with the exception of lower percentage of Her2/neu overexpression. Testing for E-cadherin may have limited clinical value.
Category: Breast

Tuesday, March 10, 2009 1:00 PM

Poster Session IV # 17, Tuesday Afternoon