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INTRODUCTION Diffuse sclerosing variant of PTC (DSV-PTC) is an uncommon subtype of thyroid cancer. Although an aggressive behavior is often recognized, prognostic significance is still under debate. OBJECTIVES To describe the clinicopathological features and outcomes of a series of DSV-PTC patients. METHODS Retrospective data collection regarding 33 patients diagnosed with DSV-PTC followed at the Endocrine Department of the Portuguese Institute of Oncology in Lisbon between 1981 and 2020. RESULTS 26 patients (78.8%) were females with a mean age at presentation of 29.4±11.7 years-old. Mean time of follow-up was 19.5±10.6 years (range 0.5 to 39). Histologically, bilateral tumors were present in 72.7% patients (n=24), thyroid capsular invasion was documented in 57.6% (n=19), 45.4% (n=15) had extrathyroidal extension (ETE), and 42.4% (n=14) had lymphovascular invasion. Most patients were staged pT3 (42.4%, n=14) and pN1 (81.8%, n=27). Median lymph nodes resected were 16. None of the patients showed distant metastases at presentation. All patients were treated at least once with 131I. During follow-up, 4 patients (14.8%), with persistent neck disease, were diagnosed with distant metastases, all of them in the lung. Two patients (1.8%) presented recurrent disease in the neck after being considered with no evidence of disease. At the last appointment, 18 patients (54.5%) were in remission, 4 (12.1%) had biochemical evidence of disease, 6 had structural disease, and for 5 patients disease status was considered as undetermined. There was no disease related mortality. DISCUSSION/CONCLUSION Our study confirms that DSV-PTC is diagnosed more often in young patients and exhibits a local extensive disease at presentation. On the other hand, even in the presence of distant metastases, no patient died during follow-up.