<prompt> All of the following are helpful for diagnosis of medullary Ca thyroid except -Spindle cell stroma with few folliclesAmyloid depositionCalcitonin in stromaHistological mitochondria is essential for diagnosis  <response>: 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. 