[ANAPLASTIC TRANSFORMATION OF METASTATIC PAPILLARY THYROID CARCINOMA IN A CERVICAL LYMPH NODE - A TIMELINE].

Anaplastic thyroid cancer (ATC) is accepted as transformation of a pre-existing glandular papillary thyroid carcinoma (PTC). Anaplastic transformation within a neck PTC metastasis is extraordinary. We present a patient with an exceptional timeline of an untreated neck PTC recurrence and its rare anaplastic transformation. In 2010, a 68-year-old patient with PTC and neck metastasis, (Stage III/Stage II 7th/8th AJCC, respectively) underwent thyroidectomy and neck dissection followed with radioiodine treatment (150 mCi). In 2012, he received an additional 150 mCi following an iodine scan suggested right neck recurrence. In late 2013, ultrasound revealed a 2.3 cm, suspicious right neck lymph node (level II-III). Only in 2017, after growing to 2.7 cm, the patient consented to undergoing a fine needle aspiration. PTC was verified, yet intervention was declined. In June 2018, he presented with a rapid growing neck mass occupying right levels II,III, carotid artery encasement and jugular vein involvement. A large bore needle biopsy revealed a highly malignant tumor, surrounded by necrosis, positive for cytokeratin (CK MNF 116), thyroid lineage marker (PAX8), negative for TTF-1 and thyroglobulin, i.e., ATC. The patient passed away in November 2018. In comparison, a patient with an identical primary staging received equivalent primary treatment. Yet, among the PTC nodular metastasis found in the neck specimen, one had ATC transformation. Over a 12-year follow-up there was no recurrence. To conclude, untreated PTC neck recurrence may have long-term consequences, such as rare anaplastic transformation. Although a case study, it advocates treating PTC neck recurrence.