Absence of the BRAF and the GRIM-19 mutations in oncocytic (Hürthle cell) solid cell nests of the thyroid.

We report the first case of oncocytic solid cell nests (SCNs), found in the right lobe of the thyroid of a 70-year-old man. Conventional SCNs and 1 papillary microcarcinoma (mPTC) were also found in the left lobe. In the oncocytic SCNs, 80% of the main cells showed oncocytic cytoplasm immunoreactive for porin and proteins of the SDHB and SDHA genes. Positivity for cytokeratin 19, p63, galectin-3, and HBME-1 and negativity for thyroglobulin, thyroperoxidase, vimentin, Oct-4, and α-fetoprotein were found in oncocytic and conventional SCNs. An inverse correlation was found between oncocytic metaplasia and p63. Association with C cells was confirmed at protein and messenger RNA levels in both types of SCNs. No germinal mutation of GRIM-19 was detected. No somatic BRAF mutation was found in any of the SCNs nor in the mPTC. We conclude that SCNs may acquire mitochondrial alterations similar to those seen in follicular and C cells, as well as in their respective tumors.