Case Report and Literature Review: Neuroendocrine Thyroid Carcinoma with Negative Calcitonin

Case presentation: 60 years old, male, presented right vocal cord injury; biopsy showed undifferentiated neoplasia and immunohistochemistry as poorly differentiated Neuroendocrine Carcinoma (AE1/AE3, thyroid transcription factor 1 and Sinaptofisin positive; KI-67 90%). Neck examination revealed mass in the right thyroid, hardened and with palpable lymph nodes. Cervical tomography with expansive formation in the thyroid gland extending to the upper mediastinal and to the right vocal cord, cervical adenomegaly. There was no history of previous radiation or family history of thyroid cancer. Laboratory tests with calcitonin values, carcinoembryonic antigen, thyroglobulin and normal thyroid stimulating hormone. In the case of a neuroendocrine thyroid carcinoma with negative calcitonin (T4aN1M0, IVA), he performed 6 cycles of cisplatin-etoposide, with partial response on cervical tomography; followed for 66Gy locorregional radiotherapy, with complete response on ct scans. After 3 months of finishing radiotherapy, she had clinical worsening, presenting multiple metastatic brain and cerebellar lesions and metastatic bone lesions in costal arches, left femur, left acetabulum, imaging. Underwent cerebral radiotherapy with 30Gy, followed by chemotherapy with Carboplatin-irotecane; but progresses to death within 2 months of relapse. It was 1 year and 2 months from diagnosis to death. Discussion: Neuroendocrine tumors of the thyroid gland are generally considered as derivatives of parafollicular neuroendocrine cells (C cells) and are commonly called medullary thyroid carcinomas (CMT). Calcitonin secretion is almost always a prerequisite for the clinical and pathological diagnosis of CMT. There are neuroendocrine thyroid carcinomas that do not produce calcitonin or calcitonin-related peptide. High-grade neuroendocrine thyroid carcinomas are rare and generally have a poor prognosis. . Given the rarity of these tumors, there are no standard guidelines for prognosis and treatment, which makes prospective work impossible, making their treatment and follow-up a challenge for cancer teams. Final comments: We present a rare case of neuroendocrine thyroid carcinoma with negative calcitonin, with a good initial response to chemotherapy and radiotherapy, but with a rapid recurrence and an unfavorable outcome confirming the poor prognosis of this type of tumor.