Diagnostic Dilemma in a Thyroid Incidentaloma: Second Primary versus Metastatic Nodule?

• Published in: Journal of clinical and diagnostic research Vol. 10; no. 6; pp. PD10 - PD12
• Main Authors: Mirza, Abid Ali, Pai, Esha, Srinivas, Kodaganur Gopinath, Amarendra, Shankarappa, Gopinath, K.S
• Format: Journal Article
• Language: English
• Published: Delhi, India JCDR Research and Publications (P) Limited 01.06.2016
• Subjects: Surgery Section
• ISSN: 2249-782X; 0973-709X
• DOI: 10.7860/JCDR/2016/18279.8011

With the increasing use of 18F-Fluro-Deoxyglucose (FDG) Positron Emission Tomography (PET) the number of thyroid incidentalomas is on the rise. Focal thyroid incidentalomas identified by FDG-PET have been reported to have a high incidence of malignancy. Neuroendocrine tumours of the thyroid are rare entities. The most common neuroendocrine tumour of the thyroid is medullary carcinoma. A thyroid nodule in a patient with a known neuroendocrine tumour must be differentiated from a primary medullary carcinoma which can present as a diagnostic challenge to the clinician. A 65-year-old female patient was referred for thyroidectomy for a FNAC diagnosed follicular neoplasm of the left lobe of the thyroid, detected on FDG PET follow up. She was a known case of neuroendocrine tumour of the pancreas with no features suggestive of familial Multiple Endocrine Neoplasia (MEN) syndrome. The patient had undergone Whipple’s procedure elsewhere, 5 years back. Following total thyroidectomy, the final histopathology report was suggestive of a primary neuroendocrine tumour. We present this case to highlight the clinical dilemma in diagnosing a thyroid incidentaloma as a second primary neuroendocrine tumour versus a solitary metastatic nodule in the background of metastatic gastroentero pancreatic neuroendocrine tumour. Although clinically, a metastatic nodule should have been the obvious diagnosis, the histopathological and immunohistochemical features were in favour of a primary non-medullary Neuroendocrine Tumor (NET) of the thyroid.