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
All of the following are helpful for diagnosis of medullary Ca thyroid except - 
Select and explain. 
A. Spindle cell stroma with few follicles, B. Amyloid deposition, C. Calcitonin in stroma, D. Histological mitochondria is essential for diagnosis
D: Histological mitochondria is essential for diagnosis
Answer: D: Histological mitochondria is essential for diagnosis 
Explanation: Important Diagnostic Features of Medullary carcinoma are :
Acellular amyloid deposition.
Calcitonin secretion by tumour cells.
Microscopically polygonal to spindle cell may form nests, trabeculae and even follicles.
Electron Microscopy showing variable no. of electron-dense granules (Membrane-bound) within the cytoplasm.