ECP 2023 Abstracts

S246 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 was the most common histological form in both groups (70.32% vs. 57.53%). A total of 32.96% and 21.91% of the PTC cases in the pre- Covid-19-period and Covid-19-period, respectively, were diagnosed as microcarcinomas. Conclusion: Social isolation, online health consultations recognized as important protections against the spread of the new virus, reduced access to investigations and to elective treatment of thyroid pathology are reflected in the decrease of the thyroid surgeries during Covid-19- period. The increased incidence of PTC in 2020-2021 could be due to a bet- ter screening of patients with thyroid pathology for surgical treatment and perhaps to the delay in diagnosis and treatment of these patients. Funding: FDI Internationalization of higher education E-PS-09-007 Spindle cell metaplasia in benign nodular goiter: a rare lesion mim- icking neoplasia E.E. Cetiner*, I.E. Cakir, K. Kurt, T. Cakir, A. Kahraman *Izmir Katip Celebi University, Ataturk Training and Research Hospi- tal, Department of Pathology, Turkey Background & objectives: Spindle cell metaplasia of the thyroid gland is rarely reported and associated both with reactive processes and malignant neoplasms. Recognition of this entity and determina- tion of the cellular origin has an important clinical implication for the therapy and prognosis. Methods: In this report, we described, a rare case of benign nodu- lar goiter with non-neoplastic spindle cell component. A 50-year-old woman was admitted to the hospital with multinodular goiter. Serum levels of fT3, fT4 and thyroid-stimulating hormone were: 4,23pg/ml (2-4,4), 1,11ng/dl (0,93-1,7) and 0,124uIU/ml (0,27-4,2) respectively. Scintigraphy confirmed the diagnosis of multiple nodules with cold areas. The patient underwent total thyroidectomy. Results: Microscopic examination showed typical appearance of benign nodular goiter except the biggest nodule located in the left lobe. His- tologically, this nodule, was composed of proliferation of spindle cells showing haphazard distribution. Spindle cells exhibited bland appear- ing-elongated plump nuclei with no prominent nucleoli, atypia and mitotic figures. They were intimately intermingled with various sized thyroid follicles. Characteristic features of papillary carcinoma were not seen. Capsule of the nodule was evaluated but there was no capsular or vascular invasion. Immunoreactivity with thyroglobulin, TTF1 and extremely low Ki-67 indexes proved that the spindle cell proliferation was follicular origin and non-neoplastic. CD34, calcitonin, synaptophy- sin, chromogranin, desmin and smooth muscle actin were all negative. Conclusion: There are only a few cases of benign nodular goiter asso- ciated with spindle cell component in English literature. Non-neoplastic spindle cell metaplasia can occur in follicular cells of benign nodular goiter. Detailed morphologic and immunohistochemical analyses are required to achieve an accurate histopathologic diagnosis in spindle cell lesions of the thyroid. E-PS-09-008 Mixed corticomedullary tumour: an unusual finding in an organ harvesting and literature review R. D’amato Pascarella*, S. Uccella, M. Testa, E. Di Lauro, O. Mete, S. La Rosa *Unit of Pathology, Dept. of Medicine and Technological Innovation, University of Insubria, Varese, Italy Background & objectives: Mixed corticomedullary tumours (MCMTs) are extremely rare with only 29 cases described since 1969. Ours would be the 1 st case, as far as we are aware, to be incidentally discovered during organ harvesting. Methods: Herein, we report the gross and histopathological findings of an unexpected tumour in a 77-year-old donor male, with no relevant past medical history, during organ-removal. Frozen sections underwent pathological examination and subsequently the rest of the tumour was entirely sampled, formalin-fixed and paraffin-embedded. Furthermore, a literature review on MCMTs with the related epidemiological and clinicopathological features is hereby provided. Results: During organ-removal the pathologist on call reported a primary adrenal tumour with low malignant potential and the trans- plantation procedure was performed. The surgical specimen measured 6x5,5x2,5 cm and comprised a well-circumscribed, yellow to tawny- brown 3 cm-sized nodule, with focal areas of haemorrhage. Micro- scopically, the lesion was composed of two intimately intermingled components showing morphological and immunohistochemical fea- tures of cortical (SF1, inhibin) and medullary (chromogranin, VMAT2, GATA3, TH) cells, respectively. A MCMT was diagnosed. Neither morphological or immunohistochemical signs of malignancy were observed. In addition to ours, 28 reported cases were found in litera- ture; no data was retrievable from one additional Japanese case-report with no English version available. Conclusion: MCMTs are most common in females (20/29) and most patients occurred to be symptomatic (23/29). The mean age was 49,41 years and the mean tumour diameter 71,53 mm. Hypertension and Cushing Syndrome were reported in 20 and 12 cases, respectively, with 9 patients presenting both. Localization in adrenal glands was almost equal. Although MCMTs mostly have an indolent clinical behaviour, malignant potential should always be ruled out. Only four malignant MCMTs were reported, all of which with a poor prognosis. E-PS-09-009 Thyroid hyalinising trabecular tumour: an easily misinterpreted diagnosis O. El Mnif*, A. Zehani, H. Azzouz, B. Chelly, A. Ayari, I. Chelly, K. Bellil, S. Haouet *La Rabta pathology department Tunis, Tunisia Background & objectives: Thyroid hyalinizing trabecular tumour is a benign thyroid neoplasm that that could mimic multiple malignant thyroid neoplasms we present a case report of a 44-year-old female who had a total thyroidectomy for a highly suspicion of a thyroid carcinoma. Methods: We analysed the medical file of a 44-year-old patient with no medical history, presented a suspicious thyroid nodule classified as EUTRADS 5 with clinical and laboratory euthyroidism. The patient had a thyroid cytopunction that concluded to a papillary thyroid car- cinoma. A total thyroidectomy is performed with frozen section pro- cedures. Representative sections of the specimen were examined later under H&E stains. Results: Cytological features of the nodule were suggestive of a papil- lary carcinoma, including presence of monotonous, spindle-shaped cells with clear cytoplasm nuclear grooves and nuclear pseudoinclusions. Macroscopic examination revealed a fleshy nodule measuring 2 cm in long axis and frozen section examination revealed a proliferation organ- ized in trabeculae and in small clusters made of medium-sized cells with large nuclei sometimes presenting incisures and pseudoinclusions. The final microscopic examination showed that this proliferation was well limited without capsular invasion. It was organized in trabeculae and cords mostly with the presence of stromal amorphous material. The diagnosis of thyroid hyalinized trabecular tumour was then made. Conclusion: HTT can be challenging to diagnose preoperatively, and it can be easily misinterpreted as other thyroid neoplasms, such as medullary thyroid carcinoma or follicular variant of papillary thyroid carcinoma. E-PS-09-010 Immunohistochemistry a valuable tool for detecting BRAFV600E mutation: validation in papillary thyroid carcinomas S. Emoke-Andrea*, A. Nechifor-Boila, R. Catana, A. Borda