A 65-year-old female patient presented with complaints of a swelling in the neck which moved with deglutition along with multiple episodes of diarrhoea, hoarseness, mild dysphagia and mild shoness of breath. Lab findings revealed raised serum calcitonin levels, hypercalcemia. Histopathology slide given below From which of the structures is the structure responsible for the above condition derived from: -

This is a case of medullary carcinoma thyroid. Image C shows nuclei with neuroendocrine features (round nuclei with salt-and-pepper chromatin), amyloid deposits (fluffy appearing acellular eosinophilic material) and C-cell hyperplasia. Medullary carcinoma of the thyroid (MTC) accounts for less than 5% of thyroid cancer. MTC arises from the C cells of the thyroid, which do not accumulate radioiodine The C-cells are derived from the ultimo-branchial body which is derived from the 4th-6th pharyngeal arch. It secretes calcitonin (Ctn), which is used as a tumor marker. Patients with locally advanced disease may present with hoarseness, dysphagia, and respiratory difficulty Diarrhea may occur from increased intestinal electrolyte secretion secondary to high plasma calcitonin levels