TTF1 and carcinoma: Notably, the remaining 2 cases of ITTC without immunoreactivity to CD5 were positive for CK5/6 and p63 but negative for TTF-1, and on microscopically the tumour showed syncytial-like appearance and the pushing margins, fibrous septa and lymphocytic infiltrate of a carcinoma showing thymus-like differentiation of the thyroid gland, differentiated from primary thyroid squamous cell carcinoma (Figure 8).