Abstract 166: Tall cell subtype of papillary thyroid carcinoma- A case report of long- term follow up and literature review

Introduction: Tall cells subtype of papillary thyroid carcinoma (TC-PTC) is the most frequent aggressivevariant of PTC. Several meta-analyses have consistently reported aggressive features of thetall cell subtype as compared to conventional PTC. Consequently, 2015 American thyroid association guidelines have attributed the 'intermediate risk' category to the presence of tall cell histology alone. However, there is considerable inter-observer variability in thehistological diagnosis of TC-PTC. Moreover, the diagnostic thresholds for Tall Cell definition (in terms of height to width ratio of cells and percentage of such tall cells) have undergone revisions from time to time. We hereby describe a remarkably benign 11 years course of a young patient with TC-PTC. Case Report: A 23-year-old woman (at the time of diagnosis in 2011) underwent evaluation for a palpable thyroid nodule. USG showed 2 cm x 1 cm solid nodule in left lobe of thyroid. FNAC wasreported as lymphocytic thyroiditis. However, the patient chose to undergo surgery. A total thyroidectomy was done. Histopathology described the presence of an infiltrating neoplasm with cells arranged in both papillary and follicular patterns in the background of Hashimoto's thyroiditis. The cells were described as large, and tall with abundant eosinophilic cytoplasm and ground glass nuclei. The final impression was given as 'papillary thyroid carcinoma with probably a tall cell variant”. She underwent a diagnostic I131 iodine scan which revealed no uptake in the neck or elsewhere because of which remnant ablative dose was deferred. In the 11 years interval of follow-up, she underwent periodic diagnostic RAI scan with stimulated thyroglobulin levels which showed excellent response as per the ATA dynamic risk stratification. Discussion: Through this case, we wish to take the opportunity to discuss several clinically relevant questions regarding of TC-PTC with the appropriate search of literature including relevant meta-analysis and large volume single-center studies. Difficulties in diagnosis: Could the diagnosis be suggested pre-operatively by USG or on FNAC? What were the deficiencies in histopathology report? Prognostication of TC-PTC: Literature comparison.