[151] Clinical and Pathological Characteristics of Her2 Positive Mucinous Carcinomas: The First Assessment of a Contradictory Lesion

Christopher Flynn, Fattaneh A Tavassoli, Natalia Buza. Yale University School of Medicine, New Haven, CT

Background: Mucinous carcinoma of the breast is considered a low-grade tumor with a favorable prognosis. A majority of the cases are positive for estrogen receptor (ER) and progesterone receptor (PR) immunostains, but negative for human epidermal growth factor receptor 2 (Her2). However, a small proportion of mucinous carcinomas may overexpress Her2 and manifest a more aggressive clinical course. This study was initiated to assess the prevalence and the clinicopathological significance of Her2 expression among mucinous breast carcinomas.
Design: All mucinous carcinomas (pure and mixed) of the breast diagnosed at our institution between January 2002 and August 2011 were included in the study. All available hematoxylin and eosin (H&E) stained and immunohistochemical slides were reviewed and the clinical information was obtained from the electronic medical records. The ER, PR, and Her2 status was evaluated according to the current CAP/ASCO guidelines.
Results: During this period, 168 mucinous breast carcinomas were available for study. Sixteen cases (9.5%) showed Her2 overexpression and/or amplification by immunohistochemistry or fluorescent in situ hybridization (FISH). The patients in the Her2 positive group were younger (mean age: 51; range 36-69) than those in the Her2 negative group (mean age 65; range 24-95). The average tumor size measured 3.9 cm in the Her2 positive group compared to 1.9 cm in the Her2 negative group. The majority of the Her2 positive tumors were moderately (60%) or poorly (33.3%) differentiated, whereas over 57% of the Her2 negative tumors fell in the well-differentiated category. Interestingly, 2% of well-differentiated mucinous breast carcinomas showed Her2 overexpression. Over two thirds of Her2 positive tumors also showed ER and PR expression (triple positives), while none of the Her2 negative cases were negative for both hormonal markers. Her2 positive tumors had a higher rate of axillary lymph node metastases (30%) than the Her2 negative tumors (21%).
Conclusions: Our data demonstrate that a significant subset of mucinous breast carcinomas shows Her2 overexpression/amplification. These tumors occur in a younger patient population, have a larger tumor size, higher histologic grade, and the majority of them are triple positive.
Category: Breast

Monday, March 19, 2012 9:00 AM

Platform Session: Section B, Monday Morning

 

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