Synchronous Hürthle cell and medullary thyroid carcinomas

Hürthle cell carcinoma (HCC) and medullary thyroid carcinomas (MTC) are uncommon histological subtypes of thyroid cancers, each accounting for around 3% of all thyroid cancers. A septuagenarian woman with a history of multiple primary cancer diagnoses presented with a growing left-sided neck lump. A diagnostic left thyroid lobectomy was performed, and pathological examination found two separate malignant foci: one HCC and an MTC. The patient developed left-sided HCC nodal metastasis, and following several multidisciplinary team discussions, a right completion lobectomy with left lateral neck dissection was performed, revealing further intrathyroidal MTC and extranodal extension of HCC. We present this as the first reported case of a collision tumour of HCC and MTC, and review the available literature regarding collision tumours and their management.