Outcome after surgery and radioactive 131- iodine ablation/treatment of Papillary Thyroid Carcinoma with Desmoplastic Reaction, Our Experience Ali, I1. Abd El-Gaid, S2. Nasr, I3. Hussein, I4 and Abd Al-Monem, S5. 1Radiology Department, Faculty of medicine, Zagazig University. 2Nuclear Medicine Unit, National Cancer Institute, Cairo University. 3Oncology and Nuclear Medicine Department, Faculty of Medicine, Zagazig University. 4Pathology Department, National Cancer Institute, Cairo University. 5Otolaryngology Head and Neck Surgery Department Faculty of Medicine, Zagazig University, Egypt Egyptian J. Nucl. Med., Vol. 14, No. 1, June 2017 ABSTRACT Aim of the work: To evaluate the results of radio-active I-131treatment and the prognostic variables of papillary thyroid carcinoma with desmoplastic reaction after long-term follow-up. Material and Methods: This retrospective study includes analysis of 272 patients, post-surgery and radio-active I-131treatment of papillary thyroid carcinoma with desmoplastic reaction. Follow up period of twelve years with calculation of ten-year recurrence free and the overall survival together with the analysis of the risk factors. RESULTS: 238 Out of 272 (87.5%), showed complete response to the treatment (CR), while 34 patients (12.5%) did not have complete response. Out of these 34 patient 20 (7.4%) showed partial response (PR), 6 patients (2.2%) showed stationary disease (SD), while 8 patients (2.9%) showed progressive disease (PD). Six patients (2.2%) died during the long follow up period. The overall and the ten-year recurrence free survival was 97.5% and 89.9% respectively, in those patients with CR. Recurrence occurred within 5 years in 83.3% of patients who developed local recurrence. Conclusion: Although desmoplasia is a feature of tumor invasiveness, the prognosis of papillary cancer thyroid with desmoplastic reaction in the present study was excellent with high ten years recurrence free and overall survival. Bad prognostic factors include large tumor size, lymph node involvement, old age, vascular and capsular invasion, extra-thyroidal extension, distant metastasis and high thyroglobulin level. Key words: Differentiated thyroid carcinoma (DTC), papillary thyroid carcinoma (PTC), desmoplastic reaction, follicular thyroid carcinoma (FTC), thyroglobulin (TG).