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
[{'content': 'Which of the following features is NOT seen in papillary carcinoma thyroid? \nSelect and explain. \nA. 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', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Tumor cell immunopositivity for calcitonin', 'role': 'assistant'}]