Endocrine Abstracts

Introduction: Medullary thyroid carcinoma (MTC) is a relatively uncommon tumour of the thyroid as compared with papillary thyroid carcinoma (PTC). Concurrent of medullary thyroid carcinoma (MTC) and papillary thyroid carcinoma (PTC) in a single patient is a rare.

Case: Forty-nine year-old male patient was referred to endocrinology for multinodular goiter evaluation. He had no palpable nodules. There was no apparent family history of endocrine disorders or external radiation therapy. The thyroid ultrasound showed an isoechoic nodüle 9 mm in size, in the left lobe and two hypoechoic nodes on the right lobe 4.4 and 7 mm in size, with accompanying linear calcification. The patient was euthyroid, serum calcium level and antithyroid autoantibodies were normal. Fine needle aspirations cytology demonstrated a suspicious for PTC. The patient underwent total thyroidectomy. The histology and immunohistochemistry showed multifocal papillary microcarcinoma (5mm- in the right lobe/7mm in the left lobe) and medullary microcarcinoma (3 mm-in the right lobe). Postoperatively calcitonin level < 0.2 pg/ml, and thyroglobulin level <0.1 ng/ml. Radioiodine treatment was not performed. Urinary metanephrines levels were in normal ranges. RET protooncogene was found to be negative.

Discussion: The simultaneous occurrence of MTC and DTC in thyroid gland can be observed in two main settings: a mixed tumor showing dual differentiation or a collision tumor showing two separate different carcinomas. The latter category nodules with MTC and PTC were detected distinct locations, seperated by normal thyroid area. Pathogenesis of these tumors is unclear. The collision theory is suggested that two independent tumors are located in the gland by coincidental. Other possible explanations for these tumors the presence of RET protooncogene mutation in both type thyroid cells. Recent studies and our case suggested that MTC and PTC are usually coincidental and independent. Endocrinologist and pathologist should to be alert in this condition.