A Case of Medullary Thyroid Carcinoma Diagnosed With Sustained High Level of Procalcitonin in a Critically Ill Patient. The Importance of Clinical Suspicion

Abstract

Medullary thyroid carcinoma (MTC) is a thyroid cancer that originates from the parafollicular C cells and accounts less than five percent of all thyroid cancer cases [1]. It can be sporadic or part of a familial syndrome [2]. Diagnosis in the routine clinical practice is difficult since the detection rate is low with fine needle aspiration and the ultrasonographic features are not reliable [3]. Although serum calcitonin is the most accurate marker for the diagnosis there is no specific cut off for excluding MTC with certainty and different potential cutoff values have been reported in literature [4]. There are also few cases of MTC without calcitonin elevation in the literature [5]. Serum calcitonin levels can vary during the day because of its pulsatile secretion [6]. Calcitonin also can be in different immunoreactive isoforms leading different results with different assays. Moreover, calcitonin is an unstable peptide and is rapidly degraded by protease enzymes in the room temperature. Even it is refrigerated 23% decays in the first twelve hours that can lead a false test result [7].