Coexistence of medullary and papillary thyroid carcinoma in the same lobe-isthmus complex: A case report.

The occurrence of coexisting papillary thyroid carcinoma (PTC) and medullary thyroid carcinoma (MTC) in a single thyroid lobe is considered to be uncommon. A 47-year-old male presented with progressive anterior neck swelling. Upon imaging, the diagnosis of papillary thyroid carcinoma was made and the patient underwent total thyroidectomy and right selective neck dissection. Histopathological examination demonstrated that medullary carcinoma was located within the right lobe and follicular variant PTC was located within the left lobe and isthmus regions. Upon evaluation of the cervical lymph nodes, metastatic medullary carcinoma was noted. Confirmation of the presence of calcitonin in the MTC component and thyroglobulin expression in the PTC component through immunohistochemistry illustrated the importance of using meticulous histopathological and immunohistochemical analysis in making accurate diagnoses and providing individualized treatment options.