The Importance of Lymph Node Dissection in Medullary Thyroid Carcinoma Management

Abstract

\n Medullary thyroid carcinoma (MTC) is a rare endocrine malignancy that arises from calcitonin (Ct) parafollicular C-cells. Most cases are sporadic with frequent presentation being a solitary thyroid nodule. Total thyroidectomy with central neck dissection of lymph nodes (LN) is the standard treatment for MTC. The need for lateral neck dissection is controversial, with poor efficacy of non-surgical treatments presenting a problem. We present a case of MTC with preoperative Ct >500 pg/mL and negative imaging for metastases who underwent total thyroidectomy without LN exploration with an excellent postoperative biochemical response.\n This is a case of a 52-year-old female with a three-year history of anterior neck growth. The repeat fine needle aspiration (FNA) of a, previously negative for malignancy, growing nodule was consistent with MTC. Preoperative Ct and CEA levels were significantly elevated, 834.0 pg/mL and 11.2 ng/dL, respectively; a preoperative pan- CT scan did not reveal any suspicious LN or metastatic lesions and a negative RET oncogene mutation with normal plasma normetanephrines and metanephrines suggested a spontaneous rather than familial MTC. Patient underwent total thyroidectomy without LN exploration. Pathology confirmed MTC stage T1b. The one and three months postoperative follow up showed a significant downtrend with no normalization of Ct and CEA levels, 9.1 – 9.2 and 11.1 – 1.2, respectively. Reoperation for central and lateral neck dissection was considered; however, given the excellent biochemical response as well as the lack of radiographic evidence of disease, it was decided to continue monitoring of Ct and CEA levels for now.\n MTC response is monitored by the postoperative serum Ct and CEA levels when compared to the preoperative values. Serum Ct serves as a sensitive tumor marker, which is thought to have correlation with malignancy mass size and its cellular differentiation. The term biochemically cured, refers to the postoperative normalization of CEA and undetectable levels of Ct which carries a 5-year recurrence of 5%. It is believed that the higher the levels and the faster doubling time of these tumor markers the worse is the prognosis. In addition, it is suggested that patient’s age and extent of disease at the time of surgery are proportionally correlated with disease recurrence. However, there are reports of large MTC metastatic deposits with low serum Ct and CEA, rising up the hypothesis that levels reflect cell production potential for tumor markers rather than the number of cells. Reoperation rarely results in biochemical cure, but it may slow disease progression. Normal postoperative Ct levels predict cure; however, the clinical course of those with upper normal limit levels postoperatively is markedly variable. Careful regular biochemical and imaging follow-up will be of the utmost importance for the patient presented in this case.