Isolated poorly differentiated cancer (insular) in a thyroglossal cyst: a case report

A 23-year-old young man presented with a painless neck mass that he noticed slowly growing over the past 4 years. Neck imaging showed an irregular 5 x 5 cm mixed solid and cystic mass in mid neck that looked suspicious but normal looking thyroid and no neck lymphadenopathy. Thyroid uptake scan was within normal also. Fine needle biopsy (FNA) from thyroglossal cyst (TGC) was malignant, Bethesda VI. Multi-disciplinary meeting discussed the case and advised for removal of both the TGC cancer and total thyroidectomy. After patient counseling, he underwent Sistrunk procedure for excision of the TGC mass and total thyroidectomy. histopathological examination revealed a poorly differentiated carcinoma of insular type in TGC with unremarkable thyroid gland. Patient recovery was uneventful. Post-operative multi-disciplinary meeting discussed the histopathology results and advised for post-operative radioactive iodine therapy (RAI) and thyroxine suppression followed by serum thyroid stimulating hormone (TSH) and thyroglobulin (TG). We shall review the diagnostic and management considerations of our case having this rare cancer.