[248] Comparison of Genomic Instability in Mucinous A and B Carcinomas of the Breast.

Alma Sanchez-Salazar, Shelly R Gunn, I-Tien Yeh. UTHSCSA, San Antonio, TX

Background: Mucinous carcinomas of the breast are tumors in which at least one third of the volume of tumor is comprised of extracellular mucinous secretions. Type A is defined as a paucicellular tumor with no neuroendocrine differentiation, whereas type B is defined as hypercellular with neuroendocrine differentiation. Previous molecular analyses have found mucinous tumors to have a low level of genomic instability. The purpose of this is study is to compare the level of genomic instability of type A to type B mucinous carcinomas.
Design: 25 mucinous breast carcinomas with fresh frozen tissue were retrieved from our files. The cases were reviewed for H&E histological features of type A or B and estrogen and progesterone receptor expression by immunohistochemistry. Representative sections of the tumors were dissected from the normal tissue present in the blocks and subjected to microarray comparative genomic hybridization using Agilent (Santa Clara, CA, USA) human genome CGH microarray kit 105A. Analyses were performed using Agilent genomic workbench 5.0 software.
Results: All mucinous carcinomas were estrogen and progesterone receptor positive. 24 of the cases were pure mucinous carcinomas (19 type A and 5 type B) and one mixed mucinous and ductal carcinoma (type A). 11/20 type A and 4/5 type B mucinous carcinomas showed a complex level of genomic instability with three or more (up to 12) of the chromosomes showing instability. There were no abnormalities found in 4 type A and 1 type B tumors. The remainder showed a low level of genomic instability (5 type A). Of the most complex cases (showing 7 or more chromosomes with genomic instability), 4 were type A and 3 were type B mucinous carcinomas. Chromosome 1 was most frequently abnormal: 1p partial loss (2 type A, 2 type B) and 1q full gains (6 type A and 2 type B). Chromosome 16 showed q loss in 8 cases, including 7 type A and 1 type B. 4 cases showed concurrent 1q gain and 16q loss, including 3 type A and 1 type B.
Conclusions: There does not appear to be a difference in genomic instability between type A and B mucinous carcinoma with both types showing a range of low to high genomic instability. 4/25 mucinous carcinomas, including 3/20 type A and 1/5 type B, showed the classical pattern of low-grade invasive ductal carcinomas, with concurrent 1q gain and 16q loss.
Category: Breast

Monday, February 28, 2011 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 24, Monday Morning

 

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