B71
Genome-wide SNPLOH analysis of intracystic papillary carcinoma of the breast
Angela Jones1, Sarah Pinder2, Cheryl Gillett2, Ian Tomlinson1, Elinor Sawyer2
1Wellcome Trust Centre for Human Genetics, Oxford, UK, 2Kings College London, UK
Background
Papillary lesions of the breast are a heterogeneous group of lesions ranging from benign (papilloma) to malignant (intracystic papillary carcinoma, invasive papillary carcinoma). Papillomas are common (10% of benign breast tumours), intracystic papillary carcinomas are rare representing less than 1% of all breast cancers. In contrast to invasive papillary carcinoma, intracystic papillary carcinoma tends to occur in elderly women and behaves in an indolent fashion. It is considered to be either a variant of DCIS or a form of low grade invasive carcinoma and may form part of a spectrum of progression from in situ to invasive disease.
Aim
To characterise genetic changes in intracystic papillary carcinoma and elucidate further the pathway of papillary carcinogenesis within the breast
Method
16 intracystic carcinomas (7 solid variant) were identified from the Guys Breast Tissue Tumour Bank. SNP-LOH was performed using the Illumina Goldengate Assay. Copy number changes were confirmed using Agilent CGH Arrays. All tissue was FFPE.
Results
Gains, deletions and copy neutral LOH were common in these tumours. All tumours showed some genetic changes. The average number of chromosomes undergoing genetic change was 10 (range 3-18). The commonest change occurred on 16q (50% showed deletion, 18% copy neutral LOH). The second most frequent change was on chromosome 13 (31% copy neutral LOH, 18% deletion), 44% had gain of 1q and 38% deletion on chromosome 11. Interestingly the solid variants had a different profile, with 43% showing copy neutral LOH on 2q and gain of 8q.1q gain and 16q loss were less common in this subgroup.
Conclusion
This is the first genome wide genetic analysis of these tumours and shows that despite their indolent behaviour intracystic papillary carcinomas have multiple genetic changes characteristic of invasive disease. The solid variant appears to have a different genetic profile.
