Concurrent Lymph Node Metastases of Medullary and Papillary Thyroid Carcinoma in a Case With Ret Proto-Oncogene Germline Mutation

Introduction: The simultaneous occurrence of medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC) is rare with a reported prevalence of 0.28–2.6%. Adding to the rarity is the concurrent lesion within the same lymph node with RET proto-oncogene germline mutation. Case Report: A 36-year-old male, presented with spells of headache, palpitations, abdominal pain for 1 week with no significant family history. On examination, he was found to have accelerated hypertension with solitary thyroid nodule in right lobe with no syndromic features. On evaluation, he had bilateral pheochromocytoma and MTC. Calcium profile was normal. Functional imaging showed no evidence of metastasis. A probable diagnosis of multiple endocrine neoplasia 2 was made and genetic analysis sent. Following stabilisation of acute condition and alpha blockade, patient underwent bilateral adrenalectomy with total thyroidectomy, cervical lymph node dissection under stress steroid cover with no untoward complication. Histology showed bilateral pheochromocytoma with multifocal MTC involving both lobes of thyroid with classic PTC in right lobe, few central cervical lymph nodes showing dual tumour deposits. Genetic analysis showed missense high-risk RET (p Cys634Arg) mutation. Family screening showed similar mutation in his asymptomatic son, later underwent prophylactic thyroidectomy. Discussion: The generally accepted hypotheses for coexistence of MTC and PTC are stem cell, collision effect, and hostage theories. Collision effect theory figures the tumour to be composed of two different and asunder moieties. Conclusion: Systematic evaluation of patient symptoms is important. Early identification by genetic screening and prophylactic total thyroidectomy avoided the occurrence of complications of aggressive MTC.