Metastatic Moderately Differentiated Neuroendocrine Carcinoma Of The Larynx Mimicking Medullary Thyroid Cancer

ABSTRACT Objective: The objective of this report is to describe a case of metastatic moderately differentiated neuroendocrine carcinoma (MDNC) of the larynx with markedly elevated serum calcitonin levels mimicking medullary thyroid carcinoma. Methods: We present the clinical, laboratory, and radiologic findings in a patient with an unusual clinical course of metastatic MDNC of the larynx, as well as a review of the relevant literature. Results: A 72-year-old male presented with an enlarging right neck mass. Positron emission tomography–computed tomography of the neck revealed enlarged right level III lymph nodes with compressive effect on the right internal jugular vein. Surgical resection of the lymph nodes was consistent with metastatic medullary carcinoma. Immunohistochemical staining was positive for cytokeratin, synaptophysin, chromogranin, and calcitonin, but negative for thyroid transcription factor-1 (TTF-1). No focus of medullary thyroid cancer or evidence of C-cell hyperplasia was identified after total thyroidectomy. Review of a prior vocal cord biopsy was consistent with neuroendocrine carcinoma; cells showed strong immunoreactivity for cytokeratin, synaptophysin, chromogranin, and calcitonin, and were negative for TTF-1, S100 protein, and cytokeratin 20. Based on these findings, the presentation was consistent with metastatic MDNC. Conclusion: The unique presentation emphasizes that identifying the origin of metastatic disease and understanding the immunohistochemical pattern is important in distinguishing between metastatic medullary thyroid cancer and MDNC of the larynx. Abbreviations: MDNC moderately differentiated neuroendocrine carcinoma; MTC medullary thyroid carcinoma; TTF-1 thyroid transcription factor-1