A case report of anaplastic thyroid cancer and papillary thyroid cancer lymph node metastasis: an unusual presentation as an invasive hypopharyngeal mass.

Anaplastic thyroid carcinoma is a rare undifferentiated tumour of the thyroid follicular epithelium. It almost always develops from a pre-existing well-differentiated thyroid cancer with a co-existent thyroid malignancy varying from 5 to 17% . The co-existence of papillary thyroid cancer (PTC) with anaplastic thyroid cancer is a rare occurrence in metastases outside the primary thyroid lesion.