Unusual presentation of medullary thyroid carcinoma: Regional and distant metastases in the background of benign non-neoplastic Multi-Nodular Goiter

Background: Medullary Thyroid Carcinoma (MTC) is a malignancy that primarily arises from the C-cells of the thyroid gland with a tendency to regional and distant metastases. Methods: We report a case of a 34-year-old female with MTC where there was no evidence of primary foci of the disease within the thyroid gland, while there was a widespread metastasis in the cervical lymph nodes, lungs, abdomen, and vertebrae. Results: The patient was diagnosed with metastatic sporadic MTC based on the pre-operative work up. She underwent completion thyroidectomy with bilateral neck dissection levels II-VI. The post-operative histopathology report confirmed the diagnosis. Conclusion: The case report shows an unusual presentation of MTC. It demonstrates that there is an entity of metastatic sporadic MTC, confirmed by an abnormal calcitonin level, with unknown primary