Absence of BRAF and NRAS Mutations in Chronic Lymphocytic Thyroiditis and Primary Thyroid Lymphomas
Beenu Thakral, Jan Nowak, Mohamed Eldibany. NorthShore University HealthSystem, Evanston, IL
Background: Primary thyroid lymphomas are rare and account for 1-5% of all thyroid malignancy. A recent article described BRAF and NRAS mutation in 24% and 8%, respectively, of diffuse large B cell lymphomas of the thyroid. Chronic lymphocytic thyroiditis is presumed to be a precursor lesion for both papillary thyroid cancer (PTC) and lymphomas of the thyroid. There is scarcity of data on study of above mutations in these precursor lesions.
Design: A total of 32 cases of thyroid excisions including lobectomy and or total thyroidectomy were retrieved from our files with diagnosis of chronic thyroiditis with no PTC (n = 14); chronic thyroiditis adjacent to PTC (n = 13); and primary thyroid lymphomas with no PTC (n = 5).
Histological sections with the target areas of interest were identified and manually microdissected on 10μm sections for BRAF and NRAS mutation analysis. The isolated DNA was analyzed using a PCR based assays that amplified the region of the BRAF gene encompassing codon 600 or NRAS codon 61. Fluorescently labeled probes hybridized to those regions and a thermal melting procedure distinguished non mutated, wild type sequences from mutated sequences.
Results: The patients included 29 females and 3 males with a mean age of 45 years (range = 28-72 years). Primary thyroid lymphomas cases included DLBCL (n = 4) and Burkitt's lymphoma (n = 1). No BRAF and NRAS mutation was identified in either chronic lymphocytic thyroiditis or in primary thyroid lymphomas. However, BRAF was mutated in 61% of PTC.
Conclusions: We found no evidence of BRAF and NRAS mutations in 27 cases of chronic thyroiditis in our study. These results do not support that chronic lymphocytic thyroiditis is a precursor to BRAF or NRAS mutated primary thyroid lymphomas, or that such mutations are a late event in that progression.
Category: Head & Neck
Tuesday, March 5, 2013 9:30 AM
Poster Session III # 141, Tuesday Morning