Mixed medullary-follicular thyroid cancer treated with surgery and radioiodine ablation: An illustrative case

Abstract

Introduction: Differentiated thyroid cancer is the commonest cancer affecting thyroid gland. Medullary thyroid carcinoma (MTC) constitutes only 2-8% of all thyroid cancers. Simultaneous occurrence of mixed medullary and follicular thyroid carcinoma (mixed MTC-FTC) is rare. This may pose challenges in diagnosis, treatment, follow up and future prediction of prognosis. Case presentation: A 24 -year-old female presented with a neck swelling that increased in size over 2 months period. She was clinically and biochemically euthyroid. Thyroid Technetium Pertechnetate (99mTcO 4 ) scan showed a cold nodule in the right lobe and ultrasound thyroid confirmed the presence of hypo-echoic well defined lesion. Fine needle aspiration biopsy (FNAB) revealed a medullary thyroid cancer. She underwent total thyroidectomy and lymph node dissection. The histopathology showed a solitary tumor with mixed features, predominantly medullary with areas of follicular architecture, confirmed by immunohistochemical staining as mixed MTC-FTC. Work up for MEN II and RET-proto-oncogen was negative. Postoperative isotope scan showed an increased uptake in the remnant thyroid tissue. She was treated with adjuvant radioactive iodine therapy. Her initial calcitonin level post operatively was 13.4 pg/ml (NR < 5.0), CEA 36 ng/ml (NR <3.8), and thyroglobulin was 0.7 ng/ml (NR <1). On follow up visits, the thyroglobulin as well as calcitonin and CEA levels were all suppressed. Conclusion: Cases of mixed follicular and medullary cancer present significant diagnostic and management challenges. Although we have managed our case surgically as well as by radioactive iodine and we are satisfied that follow up with calcitonin and thyroglobulin did not show any evidence of recurrence, we propose that mixed tumors be included in thyroid cancer management guidelines.