Sporadic Micromedullary Thyroid Carcinoma With Bone Metastases At Diagnosis: A Case Report And Review Of The Literature

Abstract

Objective: Describe a case of sporadic micromedullary thyroid carcinoma (mMTC) found to have bone metastases at the first presentation. Methods: We present the initial clinical manifestations, pathology findings, laboratory results, and management of a patient with mMTC. Literature related to mMTC and its presentation was reviewed. Results: A 35-year-old female presented with a neck mass in 2012 and was found to have a left level IV cervical lymphadenopathy. Fine needle aspiration (FNA) revealed benign lymphoid tissue. She was kept under observation but a repeat FNA of the same persistent lymph node one year later revealed a low-grade neuroendocrine tumor. Serum calcitonin was 1,996 pg/mL (reference range: 0.0 to 5.1 pg/mL) at this time. Computerized tomography demonstrated multiple sclerotic lesions in the spine, ribs, and pelvis that were suspicious for metastatic lesions. A neck ultrasound revealed a subcentimeter, hypoechoic thyroid nodule in the lower isthmus and suspicious neck lymph nodes. The patient underwent total thyroidectomy with bilateral modified radical neck dissection. Tumor stage was pT1a pN1b M1 based on the identification of a 2-mm mMTC in the left lobe with lymphovascular space invasion and metastatic medullary thyroid cancer (MTC) involving 17 left side neck lymph nodes. A biopsy of her right iliac bone lesion was consistent with metastatic MTC. She underwent adjuvant radiation therapy to the neck. She did not have a germline ret proto-oncogene mutation and preoperative catecholamines were normal. Conclusion: Sporadic mMTC can rarely have distant metastases at the initial presentation and is associated with poor prognosis. Abbreviations: ATA = American Thyroid Association; CT = computerized tomography; Ctn = calcitoninFDG = fluorodeoxyglucose; FNA = fine needle aspiration; mMTC = micromedullary thyroid carcinoma; MTC = medullary thyroid cancer; PET = positron emission tomography; RET = ret proto-oncogene