CLINICAL AND PATHOLOGICAL FEATURES OF AGGRESSIVE VARIANTS OF PAPILLARY THYROID CARCINOMA: A CASE SERIES AT A BRAZILIAN INSTITUTION

Introduction: Papillary thyroid carcinoma (PTC) is the most common endocrine malignancy with aggressive variants being recognized. Some of these variants can have higher rates of metastasis, recurrence, resistance to radioactive iodine therapy. Objective: Here we report our case series of aggressive variants of PTC, focusing in frequency and clinical and pathologic characteristics. Methods: Retrospective study was performed from all thyroid specimens registered at Oswaldo Cruz German Hospital from 2016 to 2020. Pathologic reports with CAP based checklist data were reviewed as one of aggressive variants recognized in literature: tall cell, hobnail, diffuse sclerosing, solid variants. Pathological information (tumor size, multifocality, margin status, pT, pN stage) clinical data (age, sex, comorbidities) were evaluated by reviewing the medical records. Results: A total of 664 thyroidectomies were performed with 322 (48%) cases of PTC. From these, 57 (17.7%) were recognized as aggressive variants: 35 (61%) tall cell variant, 4 (7%) hobnail variant, 9 (16%) diffuse sclerosing variant, 9 (16%) solid variant. Among these, 68% females, median age at diagnosis 46.5 years (range 24–81 years), 29 (51%) pts had no comorbidities and only 6 had smoking history. On pathological examination, 31 (54%) disclosed multifocality, 24 (42%) present in both thyroid lobes. Thirty five (61%) had direct extension into perithyroidal soft tissue, 24 (42%)lymphatic vessel invasion, 14 (25%) blood vessel invasion, 8 had both, 3 perineural invasion. Across 8th AJCC, our cases were classified as stage I (50 cases, 88%), II (7 cases, 12%) and 26 (46%) pts were treated with one dose of adjuvant radioactive iodine. Conclusion: Aggressive variants of PTC are a frequent pathologic diagnosis in our cancer center and careful examination of surgical specimen is important to their recognition. Our practice is focused in private healthcare system therefore the majority of patients were diagnosed in stage I disease owing to ultrasound wide availability. Long term follow-up data and comparison with non-aggressive variants will be necessary to evaluate the clinical relevance of a precise diagnosis of these variants in our context.