ECP 2023 Abstracts

S23 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 Methods: Retrospective study assessing papillary carcinomas diag- nosed in surgical specimens from 2005 to 2020 in a central university hospital. We recorded sex, age and tumour size. The clinical evolution of tumours with ≤5 mm and their clinical evolution was registered. Those associated with other thyroid neoplasms (malignant or low-risk) were excluded. Results: 1288 total cases of papillary carcinoma 557 of which were microcarcinomas. Of those 20 were excluded due to a concurrent malignant or low-risk thyroid neoplasm. 311 of the remaining cases had ≤5 mm. 265 patients were female and 46 male. The follow-up average period was 70.8 months and the age 58.2. 32 died during the follow-up, all unrelated to the microcarcinoma. 10 had focal invasion of extrathyroid tissue and 3 were pN1 at the diagnosis. During the follow- up there were 0 recurrences, 1 lymph node and 1 lymph node and bone metastasizing averaging 7 months after diagnosis. All of these patients were female. One case of pN1 showed tall cells. Conclusion: In this series of 311 cases of papillary microcarcinoma with ≤5 mm 1.6% of patients developed lymph node or distant metas- tasis. Despite these cases no patient died due to thyroid disease. No matter the size it seems that papillary carcinoma of the thyroid gland can spread and some aspects like the presence of tall cell com- ponent should be searched when studying this specimens as they are known predictors of worse prognosis. OFP-06-002 Utility of HAND2 immunohistochemistry in the differential diag- nosis of neuroendocrine neoplasms M. Manethova*, V. Stejskal, J. Drugda, M. Hácová, H. Hornychová, D. Netuka, T. Česák, F. Gabalec, A. Ryška, J. Soukup *The Fingerland Department of Pathology, Charles University, Fac- ulty of Medicine in Hradec Králové and University Hospital Hradec Králové, Czech Republic Background & objectives: Together with Phox2B and GATA3, Hand2 is a transcription factor responsible for terminal chromaffin differentiation of neuroendocrine cells. However, there are no data to this date addressing the immunoreactivity of Hand2 in different neuroendocrine neoplasms. Methods: Tissue microarrays or whole sections of 64 well differ- entiated neuroendocrine tumours (WDNET), 29 neuroendocrine carcinomas (NEC), 47 paragangliomas (PG), 6 olfactory neuro- blastomas (ONB) and 21 cauda equina neuroendocrine tumours (CENET) were stained with Hand2 antibody (EPR19451, 1:150, Abcam). The percentage of positive cells and staining intensity was assessed as H-score by two independent observer pathologists. Results: All examined PGs (100%, 47/47) were Hand2+ (median H-score 175; IQR 90-280), while only 12.5% (8/64) of WDNETs were Hand2+ (5 lung and 3 appendix tumours, median 11; IQR 5.7-15.3). Rare positive cells were noted in 9.5% (2/21) of CEN- ETs and 3.2% (1/29) NECs (all H-score 2), while all ONBs were negative. Compared to WDNETs, PGs showed significantly higher H-score (P<0.001) and parasympathetic PGs had significantly higher H-score, compared to sympathetic PGs (median 280 vs 122.8; p<0.001). For a positive identification of PG, the ROC analysis proposed cut off values of H-score 21,5 (sensitivity 89,4%, specificity 100%) and cut off values of positive cell percentage 8,3% (sensitivity 95,8%, specificity 100%). Conclusion: In neuroendocrine neoplasms, Hand2 is consistently observed in paragangliomas, while it is only rarely seen in other neu- roendocrine tumours. This might be of diagnostic use. Funding: BBMRI-CZ LM2023033; Charles University Cooperatio Program, research area DIAG and METD; Czech Ministry of Defense MO 1012; The European Regional Development Fund-Project BBMRI-CZ Biobank network – a versatile platform for the research of the etiopathogenesis of diseases, No: EF16_013/0001674. OFP-06-003 How far can we go grading medullary thyroid carcinoma on fine needle aspiration? C. Ariño-Palao*, A. Ferrer-Gomez, M.R. Meléndez Gispert, H. Pian-Arias, A. Benito-Berlinches, I. Ruz-Caracuel *Pathology, Ramón y Cajal University Hospital, IRYCIS, Madrid, Spain Background & objectives: Latest WHO Classification of Endocrine Tumours has included histopathological grading of medullary thyroid carcinoma (MTC) but its use is still discouraged on fine needle aspi- ration (FNA) due to the absence of studies. We aim to study grading features on FNA. Methods: FNA smears from 18 patients with MTC diagnosed on surgical specimens, were blindly reviewed. We annotated cytologi- cal features such as predominant pattern, necrosis, mitosis, amyloid, and pleomorphic cells. The value of different cytological stains was also assessed. Lastly, we compared our findings with histopathological grade and other features of their surgical counterparts. Results: Our series comprises 4 high-grade and 14 low-grade MTC. At FNA, we identified mitosis in 2 out of 4 samples from high-grade carci- nomas. Necrosis was identified in only one of these two FNA. We didn’t find any mitotic figures in low-grade cases. Nuclear characteristics and mitosis were easier to identify on Papanicolaou smears. Spindle cell pat- tern was predominant in 5 cases while 13 showed epithelioid/plasmacytoid morphology, with no distinction between grades. Amyloid was present on 14 resections, while we only identified it on 9 FNA cases with no clear dif- ference on grade. Occasional pleomorphic and multinucleated cells were present in both categories but appeared on all high-grade cases. Conclusion: We were not able to identify all high-grade carcinomas on FNA. However, the two cases with the highest proliferation index (above 6%) in the surgical specimen, were identified by the presence of few mitosis on smears. Although MTC grading cannot be performed on FNA, the identification of mitotic figures should be highlighted as suspicious of high grade MTC. In this setting, Papanicolau staining can facilitate mitosis identification. OFP-06-004 Are prognostic cutoff values for WHO grade parameters and foci of vascular invasion accurate when applied to papillary thyroid carcinoma? A case control validation analysis G. Tallini*, P. Mancuso, G. Besutti, A. De Leo, S. Coluccelli, T. Maloberti, F. Chiarucci, D. Giordano, F. Torricelli, A. Ciarrocchi, D. de Biase, A. Frasoldati, S. Piana, P. Giorgi Rossi, M. Ragazzi *Department of Medical and Surgical Sciences (DIMEC), University of Bologna Medical Center, Bologna, Pathology-IRCCS Azienda Ospedaliero-Universitaria di Bologna, Italy Background & objectives: Necrosis and/or mitoses define high- grade papillary thyroid carcinoma (PTC). It is unclear whether extent of angioinvasion is prognostic. Cutoffs at ≥5 mitoses/2mm2 and >4 angioinvasive foci are empirically defined. We aim to identify optimal cutoff values predictive of distant metastases. Methods: We analysed 50 consecutive PTC cases with distant metas- tases (DM-PTC): 16 synchronous, 34 metachronous. One-hundred- eight matched cases with non-metastatic PTC (N-DM-PTC, 10-year minimum follow-up) were used as controls. Necrosis, mitoses, and angioinvasion were quantified. ROC analysis was performed and area under the curve (AUC) values determined to define the best sensitivity and specificity cutoffs predictive of distant metastases. Results: Metastases were associated with necrosis (any, no cutoff: 43.8% all DM-PTC, 53.1% metachronous DM-PTC vs 5% N-DM-PTC; p<0.001), mitoses (p<0.001), angioinvasion (p<0.001). Cutoff ≥5 has optimal parameters based on sensitivity/specificity AUC values for