ECP 2023 Abstracts

S245 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Background & objectives: Anaplastic thyroid carcinoma (ATC) with osteoclast-like giant cells is an exceptionally rare entity. It can resemble other tumours with giant cell feature arising in the neck or elsewhere. Establishing the thyroid origin is crucial given prognostic and treatment implications. Methods: We report the case of a 78 year-old female admitted to the hospital for a rapidly growing tumour mass on the left lobe of the thy- roid with compressive symptoms like dysphagia, dysphonia, shortness of breath. As FNA cytology was malignant, a total thyroidectomy with lymph-node dissection was performed, and the specimen was sent to the Pathology Department. Results: On macroscopy, the left right lobe was almost entirely replaced by a whitish tumour widely crossing the resection limit. On microscopy, the tumour was made of highly pleomorphic spindle and epitheloid cells, interspread with numerous osteocleast-like giant cells. More than 10 mitosis/mm² were counted, and no necrosis. A small contingent of tall cell variant of papillary thyroid carcinoma (TC-PTC) was noticed. No transition between ATC and TC-PTC was observed. On immunohistochemistry the anaplastic cells were negative for AE1- AE2, TTF1, PAX8, Thyroglobuline and positive for P53 and BRAF (BRAF V600 E mutation confirmed by IDYLLA technique). TC-PTC cells were positive for all markers, except P53. The osteoclast-like-cells were positive for CD68. Conclusion: BRAF positivity, confirmed by PCR based molecular testing of the BRAF mutation is of capital importance in establishing the thyroid origin of ATC with osteoclast-like giant cells, as all other markers witnessing the follicular origin of the tumour are negative. This is an important step in order to etablish an accurate management of patients exhibiting this very aggressive and deadly cancer. Funding: FDI project 2023 - Internationalization of higher education E-PS-09-004 Reclassification of papillary thyroid carcinomas into differentiated high-grade thyroid carcinomas using criteria of the WHO classifi- cation of Endocrine and Neuroendocrine Tumours (5th ed.) V. Cancer Huerva*, A. Pinedo Estalayo, B.S. Pacheco Martinez, M. Pinedo Estalayo, C. Vasquez-Dongo *Hospital Universitari de Girona Doctor Josep Trueta, Spain Background & objectives: High-grade follicular cell-derived non- anaplastic thyroid carcinoma arises as an entity in the latest WHO clas- sification establishing criteria for Differentiated High-Grade Thyroid Carcinoma (DHGTC) diagnosis. We aim to identify and characterise DHGTC in our series of Papillary Thyroid Carcinomas (PTC). Methods: Retrospective and descriptive revision of 117 thyroid surgi- cal specimens with histopathological diagnosis of PTC from 2015 to 2019. Reclassification performed according to the latest WHO clas- sification applying the following criteria: presence of necrosis and/or ≥5 mitosis per 10 high-power fields (2 mm²). Statistical analysis was performed using chi-squared test. Results: 11 cases (9.4%) were reclassified as DHGTC with a mean age of 54 years (35-85y) and higher prevalence in women (8:1). Tumour size ranged from 1.4 cm to 3.9 cm. Histologically, six (5.2%) met necrosis criteria, accounting for up to 5% of the tumour, and five (4.2%) had high mitotic count. Classic PTC (8) architectural pattern was predominant followed by tall cell (1), solid-trabecular (1) and fol- licular (1). Seven (63%) cases presented lymphovascular invasion and nine (81%) extrathyroidal extension. Six (55%) staged as pT3 or above and five (45%) presented nodal metastasis. Within 4 years after the diagnosis, 27% DHGTC recurred without demise whereas 12.5% PTC recurred with <1% mortality. Conclusion: In our series, DHGTC had significantly higher rates of lymphovascular invasion and extrathyroidal extension than PTC (p<0.05). Moreover, we found that DHGTC presented with higher tumour diagnostic stages than PTC (p<0.05) regardless of nodal metastasis. These findings are consistent with the need of categorisa- tion of high-grade tumours. However, our results did not show statisti- cal difference in recurrence or sex distribution between these groups. The tumour necrosis percentage was low, further studies can elucidate whether a cut off value is necessary. E-PS-09-005 Papillary thyroid carcinoma presented as a hypercaptant nodule: a case report J. Caschili*, M.L. Lai, C. Gerosa, R. Murru, P. Baldussu, A. Canino, L. Secci, P.G. Calò, D. Fanni *Department of Medical Sciences and Public Health, University of Cagliari, Italy Background & objectives: Hot thyroid nodules are mostly benign and rarely show a malignant nature. Here we present the case of a 45-year-old man with papillary thyroid carcinoma that presented as a hot nodule on scintigraphy. Methods: The Fine Needle Aspiration (FNA) allowed the cytologi- cal examination of the nodule, including the immunohistochemical analysis for HBME-1 and Galectin-3 by cell block technique. Samples of the surgical specimen were formalin-fixed and paraffin-embedded to perform serial sections for H&E staining, BRAF V600E, and p53 immunohistochemical analysis. Results: Cytology revealed thyrocytes aggregated in sheets and pap- illary-like fragments with voluminous and moderately pleomorphic nuclei with finely distributed chromatin, grooves and rare pseudo inclusions. Immunohistochemical analyses performed on cell blocks showed positivity for Galectin-3 and HBME-1. Thus, the patient underwent thyroidectomy. The gross specimen showed a nodule (2.6x3x1.8 cm) occupying almost the entire left lobe. Histologically the neoplasm, lacking a capsule, showed an infiltrative pattern without margin or vascular invasion. Immunohistochemical analysis revealed a positive BRAF V600E staining and focal overexpression of p53 staining. Conclusion: Although hypercaptant thyroid nodules on scintigraphy support a benign origin of the lesion, we report the case of a papillary thyroid carcinoma presenting as a hot nodule. E-PS-09-006 Papillary thyroid carcinoma before and during Covid-19. What has changed? R. Catana*, S. Emoke-Andrea, D. Militaru, A. Borda *George Emil Palade University of Medicine, Pharmacy, Science, and Technology of Targu Mures, Romania Background & objectives: The COVID-19 pandemic declared by the WHO on 11 March 2020, produced major changes in the healthcare systems. The aim of the study was to investigate the incidence of papil- lary thyroid cancer before and during Covid-19-period in a university hospital. Methods: Patients’ clinicopathological characteristics were obtained from database registries of the Department of Pathology, Emergency County Clinical Hospital, Târgu-Mure ș , Romania. Papillary thyroid carcinoma (PTC) and all its histological variants were classified according to the 2017 WHO criteria. We analysed the data in a com- parative way between two groups: before Covid-19 (2 years 2018-2019) and Covid-19-period (2 years 2020-2021). Results: We observed a 45% decrease of the total thyroid surgeries: from 403 before Covid-19, to 219 in the Covid-19-period. The distribution of the patients from the two groups according to gen- der (W/M ratio) was: 7,7:1 vs. 6,8:1 and the average age was: 52.33 years vs. 49.89 years. The incidence of PTC, increased from 22.58% between 2018-2019, to 33.33% in the Covid-19-period. The conventional variant of PTC