Introduction: Medullary thyroid carcinoma is an uncommon primary thyroid tumour (5-10% of all thyroid malignancies) arising from parafollicular cells or C-cells. Most tumours are sporadic (75-80%) and familial syndrome multiple endocrine neoplasia; MEN-2A, MEN-2B and familial MTC in 20 to 25% cases.
Case Report: We report a case of primary medullary thyroid carcinoma in a 30 years old male patient presented with complaint of midline neck swelling. On fine needle aspiration cytology diagnosis of medullary carcinoma was suggested with a differential of SETTLE (spindle epithelial tumor with thymus like differentiation). The swelling was excised and send for histopathological examination which revealed polygonal to plump spindle shaped tumor cells, arranged in lobules separated by fibrous septa,
having abundant eosinophilic granular cytoplasm with round to oval nuclei, finely stippled nuclear chromatin and indistinct nucleoli and diagnosed as primary medullary thyroid carcinoma, confirmed on immunohistochemistry.
Conclusion: MTC is the first human malignancy known to be associated with tumour marker and hormone calcitonin. Immunohistochemistry has definite role in confirmation of diagnosis.
Amyloid, Medullary carcinoma, Procalcitonin, Synaptophysin.