This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Which of the following features is NOT seen in papillary carcinoma thyroid? 
Select and explain. 
A. Papillary structure usually complex with a fibrovascular core, B. Optically clear nuclei with nuclear overlapping, C. Nuclear pseudoinclusions and nuclear grooves, D. Tumor cell immunopositivity for calcitonin
D: Tumor cell immunopositivity for calcitonin
Answer: D: Tumor cell immunopositivity for calcitonin 
Explanation: Tumor cell immunopositivity for calcitonin