[161] Clinicopathologic and Immunophenotypic Characteristics of Triple Negative Invasive Lobular Carcinoma of the Breast

Lanie Galman, Muzaffar Akram, Jeffrey Catalano, Anibal Cordero, Dilip Giri. Memorial Sloan-Kettering Cancer Center, New York, NY

Background: 15-20% of breast cancers are triple (ER, PR, HER2) negative (TN). These tumors are clinically aggressive and are difficult to treat due to absence of target for therapy. Recently (Gucalp A et.al., Cancer Res 2011), it has been reported that about 12% of TN breast cancers express Androgen receptor (AR) and that these tumors show response to treatment with Bicalutamide (an anti-androgen agent). Although not well-recognized, a small proportion of invasive lobular carcinoma (ILC), fall in the category of TN. However, to our knowledge, there are no published studies on the characteristics of these tumors and it is not known if any of these are AR positive (+). In this study, we examine the clinical, morphologic and immunophenotypic characteristics of TN-ILC.
Design: A total of 18 cases of TN-ILC from our database (1998-2008) were identified after morphologic review and immunohistochemical (using E-Cadherin, Clone EP700Y 1:200 Epitomics, and p120, Clone MRQ-5 1:200 Cell Marque) confirmation. For comparison, a control ILC (C-ILC) group of 30 ER+ and HER2 negative was randomly selected from the Surgical Pathology files. Patient age and menopausal status were recorded. Pathologic features such as cytomorphologic characteristics (classical vs pleomorphic), mitoses, lymphovascular invasion; associated in-situ carcinoma as well as tumor size and lymph node status were assessed. Additional immunostains for MIB-1 (Clone MIB 1:200, DAKO) and AR (Clone AR441 1:300, abCAM) were also performed. Fisher exact test and t-test were used to obtain statistical significance.
Results: The mean age was 71 years (range 42-86) for TN-ILC vs. 60 (range 35-85) for C-ILC, p=0.02. 17(94%) TN-ILC were menopausal vs. 24(80%) for C-ILC, p=0.23. Mean tumor size was 2.4 cm (range 0.8-9 cm) for TN-ILC vs. 1.8 cm (range 0.5–6.5 cm) for C-ILC, p=0.31. 16(89%) TN-ILC showed pleomorphic features with apocrine morphology. In contrast, none of the C-ILC showed these features. Mean mitotic count in TN-ILC was 7.7 per 10 hpf (range 1-56) vs 43 (range 1–28) for C-ILC, p=0.23. Proliferation index measured by MIB-1 was 6%(range 1-48%) for TN-ILC and 8%(range 1-43%) for C-ILC, p=0.57. 7(39%) TN-ILC showed lymph node metastasis vs. 7(23%) of C-ILC, p=0.32. 17(95%) TN-ILC cases were AR+.
Conclusions: TN-ILC is a distinct entity with a characteristic pleomorphic & apocrine morphology. Compared to our control group, their age at presentation is older. An overwhelming majority of TN-ILC are AR+. The latter finding suggests that like other AR+ TN cancer, TN-ILC may benefit from anti-androgen therapy.
Category: Breast

Tuesday, March 5, 2013 9:30 AM

Poster Session III # 16, Tuesday Morning

 

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