Abstract
Background : Undifferentiated carcinoma of the thyroid usually arises from papillary or follicular carcinoma and is associated with a very poor prognosis. We report a rare case of undifferentiated carcinoma of the thyroid with a rhabdoid phenotype.
Case : A 64-year-old man presented with hoarseness of the voice caused by vocal cord paralysis. Ultrasonography revealed a large mass occupying the entire right lobe of the thyroid and 18F-FDG-PET/CT showed increased tracer uptake in this mass lesion. In preoperative aspiration cytology, highly atypical cells with bizarre nuclei were observed in a necrotic background. In addition, rhabdoid cells with globoid hyaline inclusions and abundant eosinophilic cytoplasm, eccentric nuclei and prominent nucleoli were scattered among the tumor cells. Total thyroidectomy and neck dissection were performed. Histological examination of surgically resected tissues revealed that the tumor consisted mostly of undifferentiated carcinoma with scattered foci of papillary carcinoma. In addition, rhabdoid cells were also found in the undifferentiated carcinoma component. The patient died of the disease 2 and a half months after he first presented with hoarseness.
Conclusion : A rare case of undifferentiated carcinoma of the thyroid with a rhabdoid phenotype is reported. The very poor prognosis of this rare type tumor should be borne in mind in the field of thyroid surgical pathology.
