Anaplastic spindle cell squamous carcinoma arising from classical papillary thyroid carcinoma with foci of columnar cell component: A case report

We report a case of the anaplastic spindle cell squamous carcinoma(SC) arising from classical papillary thyroid carcinoma(PTC) with foci of columnar cell component in a 69-year-old Chinese woman. The tumor of the right lobe was composed of spindle cell SC and PTC. Histologically,the spindle cell SC were arranged into bundles with marked cellular atypia, nuclear pleomorphism and more mitotic figures. The tumor of the left lobe was a PTC without any SC elements,which was composed of two components, namely classical and columnar cell variants PTC. The columnar cell elements occupied more than 20 % of PTC, which showed striking stratification of nuclei with no characteristic nuclei for the classical type of PTC. The patient has not received any other treatment after radical surgery. She had no tumor recurrence and other complications 13 months after operation. Only classical PTC but not columnar cell PTC and SC had been identified in 7 out of 50 excised cervical lymph nodes. In order to clarify the origin of PTC and spindle cell SC, we performed the BRAFV600E(c.1799 T > A) mutational analysis. The results of molecular analysis showed that BRAFV600E(c.1799 T > A) mutation existed in both components, which further confirmed that spindle cell SC was transformed from PTC.