Poorly differentiated carcinoma of thyroid: Case report of an uncommon entity.

Malignant thyroid tumors of follicular origin comprise a spectrum, with the indolent well-differentiated thyroid carcinoma (WDTC) at one end and lethal anaplastic thyroid carcinoma (ATC) at the other. Poorly differentiated thyroid carcinoma (PDTC) lies intermediately between WDTC and ATC in terms of morphology and prognostic standpoint. This thyroglobulin producing neoplasm accounts for 4-7% of all thyroid malignancies. PDTC has been controversial due to lack of defined diagnostic criteria. We hereby report a case of PDTC in a 42-year-old female presenting with neck swelling, pain, and dysphagia for 10 months. She was diagnosed as colloid goiter on fine-needle aspiration cytology. On imaging, a large complex thyroid with central neck nodes was seen. Total thyroidectomy and central neck node dissection were done. Based on the morphology, immunostaining, and the diagnostic criteria, a diagnosis of PDTC was made. PDTC is a diagnostic challenge due to its rarity and previous equivocal diagnostic criteria.