ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 Background & objectives: Thyroid teratomas are extremely rare neoplasms mostly presenting in newborns and their grading is based on the quantity of immature neuroectodermal tissue. Thyroblastoma is a recently described embryonal neoplasm of adults resembling thyroid parenchyma within the first intrauterine trimester. Methods: A 18-day-old female was delivered by a cesarean section at 36th gestational week due to ultrasonographically detected pleu- ral effusion. At the time of birth, a palpable mass was observed in the neck. Computerized tomography revealed a neck mass, within the thyroid tissue. The patient underwent a left thyroid lobectomy after a FNAB diagnosis of an “immature teratoma”. Results: On H&E, thyroid was almost completely replaced by the tumour. Pseudostratified ciliated columnar, intestinal and squamous epithelium; smooth/striated muscle, adipous tissue, mature cartilage, neuroglial elements and immature neuroectodermal component (INEC) were present. TTF-1/PAX8 confirmed the presence of mature residual thyroid tissue around the tumour. GFAP was positive in the INEC and the glial tissues. B-HCG, CD30, Glypican3 and OCT3/4 were negative. Ki67 index was 70% in the INEC, which occupied 10 low-power fields (LPFs). It was diagnosed as a “malignant teratoma” (grade 3) according to 2017 WHO Classification of Endocrine Tumours which recommends grading tumours with more than 4 LPFs of INEC, mitoses, and/or pleomorphism as grade 3/malignant teratoma. Conclusion: The last (2022) WHO Classification of Endocrine & Neuroendocrine Tumours states that thyroid tumours with more than 4 LPFs of INEC should be reclassified as thyroblastoma. How- ever, thyroblastoma is defined as a tumour composed of foetal-type primitive-appearing thyroid follicles, and primitive spindle cells arranged into fascicles which are absent in this tumour. We want to emphasize that there are very rare thyroid tumours that are unaware of the fact that the WHO classification has changed. E-PS-08-022 Next generation sequencing in follicular cell-derived thyroid carcinomas with poor prognosis M.R. Bella-Cueto*, R. Carrera-Salas, Á. Bonilla-Sánchez, M. Cano-Hernández, M.R. Rodríguez-Millán, J.A. Vázquez-Luque, M.d.C. Ramos-Guijo, R. Onieva Carbajo, B. Bella-Burgos, F.J. Guirao-Garriga, C.M. Blázquez-Mañá *Hospital Universitari Parc Taulí. I3PT. UAB, Spain Background & objectives: Despite the good overall prognosis, some thyroid cancer types may show unfavourable evolution (UE). Our objective is to determine the frequency and type of genetic alterations that can provide prognostic and therapeutic information in a series of cases with UE. Methods: Retrospective observational study. Subjects: patients with differentiated thyroid cancer with unfavourable evolution, poorly differentiated and anaplastic carcinomas, treated at our insti- tution between 2001 and 2019, both inclusive. Methodology: case identification, extraction of DNA, PCR, library preparation, purifi- cation and massive sequencing of optimal samples using AmpliSeq Focus Panel, AmpliSeq Library PLUS on MiSeq sequencer (illu- mina), bioinformatics analysis on Variant Interpreter (illumina). Results: Seventeen cases with optimal samples could be studied: 3 papillary carcinomas (PTC) and 2 follicular carcinomas (FTC) with UE, 5 poorly differentiated carcinomas (PDTC), three of them with UE, 3 anaplastic carcinomas (ATC), all of them with UE, 1 PTC with a minor component of PDTC and good evolution, 1 PTC with a minor component of ATC and UE, and 2 PDTC with a minor component of FTC and UE. Ten cases had pathogenic/ variant of unknown significance point mutations: 5 in NRAS (3 p.Gln61Arg and 2 p.Gln61Lys), 2 in BRAF (p.Val600Glu), 1 in EGFR (p.Arg297Cys), 1 in BRAF (p.Val600Glu) and PIK3CA (p.Glu545Lys), and 1 in NRAS (p.Gln61Arg) and BRAF (p.Asp594Asn). Conclusion: Massive sequencing has provided information about pathogenic or variants of unknown significance mutations in 10 of the 17 cases studied, although in 7 of them the alterations detected could have been identified by simpler and cheaper methods, as they correspond to NRAS mutations and BRAF V600E mutation. In two cases more than one mutation could be detected. The meaning and clinical implications of these concomitant mutations need further investigation. Funding: Fundació Parc Taulí grant. E-PS-08-023 Adrenal gland composite pheochromocytoma – ganglioneu- roma: a case report A. Stofas*, A. Patereli, K. Palamaris, H. Gakiopoulou, P. Korkolopoulou *1st Department of Pathology, School of Medicine, National and Kapodistrian University of Athens, Greece Background & objectives: Composite pheochromocytoma of the adre- nal medulla is a rare neuroendocrine tumour that represents the 1-9% of pheochromocytomas. Little is known about its biologic potential, as only seventy cases have been reported previously in the literature. Methods: We descr ibe a case of adrenal composite pheochromocytoma -ganglioneuroma in a 66-year-old female patient. After surgery, the right adrenal gland specimen was processed and examined by standard H&E technique and immunohistochemistry. Cut surface showed a grey - brown lesion measuring 4 cm. Results: Histologically, the tumour was composed of two distinct patterns. One pattern was composed of polygonal cells arranged in well-defined nests surrounded by a delicate fibrovascular stroma consistent with pheochromocytoma. The other pattern consisted of ganglion cells embedded in a schwannian stroma which was consistent with ganglioneuroma. Both components were positive for Chromogranin A and Synaptophysin but with variable inten- sities. Ganglion cells within the ganglioneuroma component and sustentacular cells within the pheochromocytoma component were positive for S-100 protein. Melan A, p504s, AE1/AE3 και Inhibin were negative. The mitotic index was <5%. Conclusion: The frequency of composite adrenal-pheochromocy- toma tumours has been reported as ranging from less than 3% of all adrenal gland neoplasms. They are treated in principle by complete surgical resection. An adequate clinical follow-up is advised for the potentially malignant neoplasms. It is difficult to predict the clinical behaviour. There are no absolute criteria for malignancy. However, features more frequently noted in malignant tumours are the presence of necrosis, vascular invasion and/or extensive local invasion, cytological atypia and high mitotic index. E-PS-08-024 Papillary thyroid microcarcinoma: characteristics at presenta- tion and evaluation of recurrence histological features M.M. Hamzaoui*, O. Belhadj, H. Azouz, B. Chelly, A. Ayari, A. Mediouni, A. Zehani, I. Chelly, K. Bellil, S. Haouet *Department of Pathology, La Rabta Hospital, Tunis, Tunisia Background & objectives: Papillary thyroid microcarcinoma (PTMC) is defined as a thyroid tumour measuring 1 cm or less and it usually S254