PMC5660805_01
(a) H&E staining of the thyroid bed and paratracheal lymph node. Top row, from left to right: (i) squamous cell carcinoma in the thyroid bed; (ii) keratin pearls of squamous cell carcinoma in higher power. Bottom row, from left to right: (i) paratracheal lymph node showing papillary feature of thyroid cancer; (ii) tall cell areas showing mitotic figure in higher power. (b) From left to right, low power showing papillary thyroid cancer and squamous cell cancer in the same field adjacent to each other.
CRIONM2017-4276435.001.jpg
PMC5660805_01_CRIONM2017-4276435.001.jpg
fig1
In addition, the left thyroid bed and a second right paratracheal lymph node demonstrated squamous cell carcinoma (Figures 1(a) and 1(b)).
(a) From left to right are the papillary tall cell variant portion of thyroid cancer staining positive for thyroglobulin, PAX8, and TTF-1 and negative for p63. (b) From left to right are squamous cell area of thyroid cancer staining negative for thyroglobulin, weakly positive for PAX8 and TTF-1, and strongly positive for p63.
CRIONM2017-4276435.002.jpg
PMC5660805_01_CRIONM2017-4276435.002.jpg
fig2
TTF-1 (very focally positive) and negative for thyroglobulin (Figures 2(a) and 2(b)). This pattern of immunohistochemistry suggests that the squamous variant seen was actually a transformation from papillary cancer unlike the primary squamous cancer which stains negative for TTF-1 and PAX8. The specimen also tested positive for BRAF mutation via immunohistochemistry (IHC).