ECP 2023 Abstracts

S82 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 chromophobe/amphophilic cytoplasm. The Ki-67 proliferation index ranged between 7-12%. Immunohistochemically, full expression of the transcription factor PIT-1 was observed, with an accompanying lim- ited expression of GH, TSH and PRL hormones as well as α-subunit expression. Overexpression of the cell cycle protein Cyclin D1 was observed in one patient. Loss of nuclear expression of ATRX protein was observed in 2 patients. Menin protein expression was retained in all patients. In all patients there was recurrence of the neuroendocrine tumour within a two-year period. Conclusion: PIT1-lineage pituitary neuroendocrine tumours include a wide spectrum of neuroendocrine tumours, the most aggressive of which is the Immature PIT1-lineage tumour/adenoma. The differential diagnosis is based mainly on the morphological features of the tumour and the representation of all three hormones of the PIT-1 cellular lineage. PS-09-004 NKX2.2 expression in several tumour types M.A. Bani*, P. Khneisser*, C. Ngo, A. Al Ghuzlan, M. Faron, J. Scoazec *Department of Medical Biology and Pathology, Morphological pathology laboratory, Gustave Roussy Cancer Campus, Villejuif, France; Paris-Saclay University, Gustave Roussy Cancer Centre, Inserm US23, CNRS UMS3655, AMMICa, Villejuif, France Background & objectives: NKX2.2 is a transcription factor that plays a role in cell differentiation in many tissues. It has been proposed as a marker for Ewing sarcoma. This study aims to determine the spectrum of expression of NKX2.2 in several tumour types. Methods: We evaluated, by immunohistochemistry, the expression of NKX2.2, neuroendocrine markers, and various transcription factors (chromogranin A and B, synaptophysin, INSM1, CD56, CDX2; PDX1, GATA3, PAX8 and TTF1) in several tumour types including neuroendo- crine neoplasms and other epithelial or mesenchymal tumours, originat- ing in different organs, diagnosed in our institution between 2021-2023. Results: We evaluated 154 cases, including 72 neuroendocrine neo- plasms (NEN), 19 Ewing sarcomas, 10 carcinomas with neuroendo- crine differentiation, 6 adenocarcinomas, 5 osteosarcomas, 4 neuroblas- tomas, 3 olfactory neuroblastomas, 4 paragangliomas, 2 Merkel cell carcinomas, 2 rhabdomyosarcomas, 2 mesenchymal chondrosarcomas. NKX2.2 showed variable expression intensity in 71 cases (49.3%). Strong diffuse staining was observed in 20 neuroendocrine tumours, 13 Ewing sarcomas, all olfactory neuroblastomas, 1 mesenchymal chondrosarcoma, [SJ1]2 poorly differentiated carcinomas. NKX2.2 expression was correlated with specific tumour types (p<0.001), the expression of INSM1 (p=0.005), chromogranin A (p=0.045), and other neuroendocrine markers. Among all NEN, NKX2.2 expression was predominantly seen in tumours originating from the pancreas and small intestines (p=0.004). Conclusion: Our preliminary results show that NKX2.2 is signifi- cantly expressed in Ewing sarcomas, NEN, olfactory neuroblastomas and mesenchymal chondrosarcoma. Among all NEN, pancreatic and small intestinal primaries were the most positive. Breast carcinomas with neuroendocrine differentiation were usually negative despite the expression of chromogranin A and synaptophysin. Correlation of NKX2.2 expression with clinicopathological features is under investigation. PS-09-005 Clinicopathological characteristics of non-syndromic familial non- medullary thyroid cancer in Santiago de Compostela (northwest Spain) J.M. Cameselle-Teijeiro*, G. Rodríguez-Carnero, C. Beiras-Sarasquete, I. Abdulkader-Nallib, M. Sánchez-Ares, M. Piso Neira, V. Pubul- Núñez, J.M. Cabezas-Agrícola, J.A. Puñal-Rodríguez *Clinical University Hospital of Santiago de Compostela, Universidad de Santiago de Compostela and Galician Healthcare Service (SER- GAS), Santiago de Compostela, Spain Background & objectives: Non-syndromic familial non-medullary thyroid cancer (NSFNMTC) is a group of hereditary carcinomas whose aetiology remains poorly understood. We investigate the char- acteristics of a case series of NSFNMTCs in comparison with spo- radic follicular-derived thyroid carcinomas (SFTCs) from the same geographical area. Methods: From our institution’s records of diagnosed thyroid carci- noma (TCs) (1991-2015), all NSFNMTCs were selected following the 5th edition WHO thyroid tumour classification (follicular cell derived carcinoma in ≥3 first-degree relatives or papillary carcinoma [PTC] in ≥2 first-degree relatives, in the absence of radiation exposure and inherited cancer syndromes). The clinicopathological features of NSFNMTCs were compared with those of the SFTCs. Results: Of the 880 follicular-derived TCs reviewed, 44 cases (5%) were NSFNMTCs and 836 (95%) SFTCs. The mean age was 42.8 years in NSFNMTCs and 52.2 in the SFTCs (p=0.006). The NSFNMTCs included 93.2% PTCs, 4.5% follicular carcinomas (FTCs) and 2.3% oncocytic carcinoma (OTC), while the SFTC group included 81.5% PTCs, 9.2% FTCs, 5.9% OTCs, 1.7% poorly differentiated carcino- mas and 1.8% anaplastic carcinomas. PTCs measuring ≤1 cm were more common in the SFTC group (45.5% versus 22.7%, p=0.001). Multifocality and bilaterality were more common in NSFNMTCs (24[54.6%] and 20[45.5%] versus 199[25.4%] and 149[19%] respec- tively, p=0.000). No significant differences were detected in tumour size, angioinvasion or associated thyroid pathology. Conclusion: NSFNMTC accounts for 5% of follicular-derived thyroid carcinomas. These patients usually present at a younger age (average ≈9 years) than with SFTCs. NSFNMTC are differentiated carcinomas, mainly PTCs, with a higher rate of multicentricity and bilaterality than SFTCs. This study has been funded by Instituto de Salud Carlos III (ISCIII) through the project PI19/01316 and co-funded by the European Union. PS-09-006 Papillary thyroid carcinoma and thyroid follicular nodular disease: a retrospective cross-sectional study of 672 cases M. de Brito Pereira*, É. Almeida, R. Ilgenfritz, A. Alves *CUF Descobertas Hospital, Portugal Background & objectives: Thyroid follicular nodular disease (FND) is a benign proliferation composed of multiple clonal and nonclonal nod- ules (1). This study aims to study the coexistence of clinicopathological features of papillary thyroid carcinoma (PTC) and FND. Methods: In a 3-year period (from 2019 to 2022), in one institution, papillary thyroid carcinoma was diagnosed in 672 cases. Those reports were revalued, the epidemiological data and the information on the anatomopathological report was collected. The epidemiological data of PTC with associated FND was compared to the cases of PTC without associated FND. The data was analysed through JASP software. Results: Of the 672 cases, 282 cases (42,0%) had PTC with FND. The average age was 54.6 years with FND vs. 46.6 without FND. The patients were predominantly women in both groups (82,7% in FND vs 76,1%). The most common presentation of PTC was unifocal lesions (61,7% in FND vs 66,2%), followed by multifocal lesions and bifocal lesions. The rate of extra-thyroidal extension was 14.2% in FND vs 18.7% with- out FND. The rate of metastases in central lymph nodes was 12.1% in FND vs 21.3%.Regarding the staging, 71.6% cases with FND vs. 62.6%