Multifocal Fibrosing Thyroiditis and Its Association with Papillary Thyroid Carcinoma Using BRAF Pyrosequencing
Renee Frank, Zubair W Baloch, Caren Gentile, Christopher D Watt, Virginia A LiVolsi. Hospital of the University of Pennsylvania, Philadelphia, PA
Background: Multifocal fibrosing thyroiditis (MFT) is characterized by numerous foci of fibrosis in a stellate configuration with fibroelastotic and fibroblastic centers entrapping epithelial structures. It is often found in thyroids with lymphocytic thyroiditis. MFT has been proposed as a risk factor for papillary thyroid carcinoma (PTC) development by initiating localized injury and stromal response, eliciting epithelial entrapment, hyperplasia and reactive atypia, proceeding to malignant transformation of follicular cells. Since activating point mutations of BRAF genes are found in approximately 40% PTCs; we attempted to identify whether MFT showed such molecular changes and could possibly be related to PTC.
Design: We identified 7 cases of PTC with MFT in our institutional pathology database and personal consult service of one of the authors (VAL) for the years 1999 to 2012. All available slides of each case were reviewed; areas of PTC, MFT, and normal tissue were selected for BRAF analysis. The areas of interest in the paraffin embedded formalin-fixed tissue were macro-dissected and DNA was extracted using institutional protocols. The extracted genomic DNA was amplified with primers which target a 122 base pair region of the BRAF gene, including codon 600. Using pyrosequencing (PyroMark Q24), the PCR product was evaluated by two sequencing primers for codon 600 mutations which were designed to detect the three most common BRAF mutations in codon 600 including V600E, V600K and V600R. We evaluated each of the specimen pyrograms for presence or absence of mutation.
Results: Each case had at least one area each of PTC, MFT, and normal thyroid tissue which was selected for macro-dissection and BRAF analysis. All of the MFT lesions and normal thyroid tissue were negative for BRAF mutations. Of the 7 PTCs analyzed, 5 (61%) were negative for BRAF mutations, while 2 cases were positive.
Conclusions: In our study, none of the MFT lesions harbored BRAF mutations whereas 39% (2 of 7) PTCs in the same gland were either positive. Hence in this small study, we found no evidence that the MFT lesion is a direct precursor to PTC. It is likely an incidental bystander in the process and a reflection of the background thyroiditis.
Wednesday, March 6, 2013 1:00 PM
Poster Session VI # 51, Wednesday Afternoon