"Triple-negative" non-secretory medullary thyroid cancer: uncommon pathological findings in a rare disease.

Abstract

Medullary thyroid cancer (MTC) is a neuroendocrine tumor that arises from the calcitonin (CT)-producing thyroid parafollicular C cells, accounting for 3–4% of all thyroid cancers [1, 2]. CT constitutes the most specific and sensitive serum biomarker of MTC and correlates with tumor size [3], whereas different markers markers, such as carcinoembryonic antigen (CEA) and chromogranin A (CgA), are specific but often co-secreted by the tumor [2, 3]. Compared with other thyroid malignancies, MTC exhibits distinctive histopathological features, and the most important immunohistochemical markers are CT and CEA; in fact, in the absence of CT expression, the diagnosis of MTC should be questioned [4]. Also, amyloid material is often present at the histological examination [4]. Calcitonin-negative medullary thyroid cancer (CNMTC), determined by normal serum levels of CT, is a very rare presentation of MTC and only a few cases have been described in the literature [5]. Moreover, CNMTC is often positive for CT immunostaining [6]. In the current case, we report a CNMTC with negative CT, CEA and amyloid substance at the histopathological examination