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Introduction: Medullary thyroid cancer (MTC) is a neuroendocrine tumor of the parafollicular or C cells of the thyroid gland, contributing to 1 to 2% of thyroid cancers. Calcitonin secreted by c cells is a sensitive tumor marker as it correlated with c cell mass and tumor burden. In this case report we would like to present a case of MTC with high calcitonin levels posing therapeutic challenge. Clinical Course: 29-year female patient presenting with 2-month history of neck swelling, ultrasound showed a 4*2 cm mass in right lobe of thyroid, with no symptoms of hypothyroidism, regular cycles and negative family history. On examination had mass in the right lobe with no palpable lymph nodes. FNAC of this lesion was Bethesda 4 with a calcitonin of 18041ng/ml. Management: Screening for pheochromocytoma and hyperparathyroidism was negative. Genetic analysis was positive for RET mutation at exon 11, p. Cys634Arg variant Ga68 DOTATOC scan was done to look for metastasis, SST positivity seen in thyroid and bilateral adrenals however plasma metanephrines were normal. Patient underwent total thyroidectomy with central compartment and bilateral neck dissection, following which patient was started on thyroxine, calcium and vitamin D supplements replacement. HPE was positive for MTC in both lobes, isthmus and the central group of nodes. Follow Up: On follow-up calcitonin levels are high (2965pg/ml 6 months post-surgery) F DOPA scan s/o avid uptake in bilateral adrenals. Chemotherapy with carbozantinib was started. 9 months post therapy, there is no significant benefit on biochemical response and hence stopped. However, after stopping chemotherapy there is no significant increase in calcitonin levels. Patient developed secondary amenorrhea 6-month post carbozantinib therapy, on evaluation has a FSH of 123.97mIU/ml. Discussion: MTC is an uncommon and aggressive thyroid cancer, total thyroidectomy with central node dissection is the main stay of treatment. TKIs have been found have promising results. However, this is a case of metastatic medullary thyroid not responding to TKIs. Treatment options in such are very few with no promising results, PRRT can be tried. Ovarian insufficiency due to TKI therapy although rare, as seen in our patient has been described in few studies. Hence has to be suspected when patient presents with irregular cycles. Conclusion: S. Calcitonin measurement predicts response to therapy and a marker of persisting disease. Functional imaging is useful in MTC to look for persistent and metastatic disease as well as diagnosing asymptomatic pheochromocytomas. Genetic analysis done preoperatively in MTC helps in risk stratification, it also guides in screening of family members. Premature ovarian insufficiency after chemotherapy is seen in this patient, women of reproductive age should be advised about oocyte preservation.
Segu et al. (Wed,) studied this question.