ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 Background & objectives: Follicular Cell–Derived Thyroid Carcinomas (FCDTC) harbour targetable molecular alterations according to their histology. It has been proposed that molecular screening to drive treatments should be based on histological classification. However, we found that distant metastases histology can bemisleading. Methods: We review the features of distant metastases of FCDTC registered in our centre from 2010 to nowadays, blinded to the primary tumour. Histological criteria evaluated included the presence of follicular pattern, colloid, papillae, psammoma bodies, squamous differentia- tion, tumour necrosis, prominent mitoses, and nuclear features of papillary carcinomas. Then, a presumed diagnosis was stablished and compared with the original primary tumour. Results: We review 15 metastases, located in bone (8), skin (3), soft tissues (1), liver (1), lung (1), and cerebellum (1). Our presumed diagnosis was follicular variant of papillary carcinoma (7 biopsies), another variant of papillary carcinoma (3 biopsies), and follicular carcinoma (3 biopsies). Two biopsies had insufficient material. Our diagnosis was concordant with the primary in 7 cases (54%) and discordant in 6 (46%). Among discrepant cases, three primary follicular carcinomas were identified as papillary carcinomas by their nuclear features. Moreover, three primary poorly differentiated carcinomas were identified as papillary carcinomas (2) and follicular carcinoma (1). Conclusion: Identification of primary FCDTC based on the histo- logical features of distant metastases can be misleading in almost half of cases. Most common causes of discrepancy are the presence of nuclear features of papillary carcinomas in the metastases and the difficulty to determine characteristics of poorly differentiated thyroid carcinomas in the metastases. PS-14-004 Peculiar facets of medullary thyroid carcinoma S.E. Giusca*, C. Andriescu, I.D. Caruntu, L. Lozneanu, D. Ciobanu-Apostol *"Grigore T. Popa" University of Medicine and Pharmacy, Romania Background & objectives: Medullary thyroid carcinoma (MTC) is characterized by a relatively aggressive biological behaviour, respon- sible for a high number of deaths compared to other thyroid cancers. We aimed to analyse the clinicopathological profile of MTC, pointing on cases with increased oncological risk. Methods: The study group comprised a single centre case series of 59 patients diagnosed at a referral hospital in North-Eastern region of Romania. The histological diagnosis of MTC was confirmed by immunohistochemical exam. Correlations between the classical clin- ico-pathological variables and three parameters considered elements of aggressiveness (thyroid capsular invasion, lympho-vascular invasion and lymph node metastasis) were settled by using statistical analysis. Results: Histopathologically, we identified the following types of MCT: conventional (35 cases/59.32%), spindle cell (12 cases/20.33%), oncocytic (5 cases/8.47%), follicular/glandular (3 cases/5.08%), pseudopapillary (2 cases/3.38%), with giant cells (1 case/1.69%) and with small cells (1 case/1.69%). Statistical analysis revealed significant correlations between tumour size and lympho-vascular invasion (p <0.0001), and lymph node metasta- sis (p=0.0220); tumour focality was significantly correlated with lymph node metastasis (p=0.0230). The chances of risk for lym- pho-vascular invasion and lymph node metastasis were associated with tumour size over 40 mm (OR=13.69, respectively OR=6). In addition, the chance of risk for lymph node metastasis was associ- ated with multifocal primary tumour (OR=9.428). Conclusion: Our results indicate that, despite the variability of histological MTC subtypes, they do not significantly influence the prognosis. A particular aspect identified in our MTC series was the association, in 7 cases, with papillary thyroid carcinoma, tumour with different cell origin; the coexistence of the two thyroid malignancies is rarely reported in the literature. Moreover, our data confirm that lympho-vascular invasion and lymph node metasta- sis are relevant indicators for aggressiveness, whose presence can explain the worse course of disease. PS-14-005 Non-syndromic familial non-medullary thyroid carcinoma in the area of Santiago de Compostela (northwest Spain) J.M. Cameselle Teijeiro*, C. Beiras-Sarasquete, I. Abdulkader- Nallib, M. Sánchez-Ares, M. Piso-Neira, G. Rodríguez-Carnero, V. Pubul-Núñez, J.A. Puñal Rodríguez *Clinical University Hospital, University of Santiago de Com- postela and Galician Healthcare Service (SERGAS), Spain Background & objectives: Non-syndromic familial non-medullary thyroid carcinomas (NSFNMTCs) are a heterogeneous group of hereditary cancers whose genetic basis is poorly understood. It has been suggested that some of their clinicopathological features may suggest a familial character. We investigated a series of NSFNMTCs. Methods: Follicular cell-derived thyroid carcinoma was identi- fied in ≥ 2 first-degree relatives in 43 cases. Most patients were women (69.76%), with a female-to-male ratio of 3:1.3. The mean and median age (and range) was 42.5 and 67 (25-73) years for women, 43.08 and 43 (18-68) for men and 42.33 and 41 (18-68) for the total number of patients, respectively. Results: All cases (97.67%) were papillary thyroid carcinomas (PTCs) except one case of oncocytic thyroid carcinoma. PTC subtypes were: follicular (54.76%), conventional (28.57%), tall cell (11.9%), oncocytic (2.38%) and Warthin-like variant (2.38%). Multifocality was detected in 31/43 cases (72.09%) and bilaterality in 24/42 cases (57.14%). Tumour size ranged from 3 to 56 mm (mean 17.55; median 12). Venous invasion was found in 1 case (2.32%); extrathyroidal extension in 6 (13.95%) and lymph node metastases in 10 (23.25%). Follicular nodular disease and/or follicular adenoma was detected in 30 cases (69.76%); lymphocytic thyroiditis in 13 (30.23%); Graves disease in 2 (4.65%); intrathyroidal parathyroid in 3 (6.97%) and thymic tissue in 1 case (2.32%). Conclusion: NSFNMTCs are typically PTCs, mainly of the follicular, conventional and tall cell variants, associated with multifocality and bilaterality, as well as with a high frequency of extrathyroidal extension. The combination of PTC with a background of benign lesions is also frequent. Funding: Partially supported (JMC-T) by grant PI19/01316- FEDER, Instituto de Salud Carlos III, Spain. PS-14-006 The incidence trend of non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) in Mures county, Romania, five years after the introduction of this new entity: a retrospective cohort study D. Burlacu*, A. Nechifor- Boila, E. Szasz, R. Catana, A. Borda *Pathology Department, Emergency County Hospital Tg. Mure ș , Romania Background & objectives: NIFTP nomenclature was proposed in 2016 and revised in 2018. The aim of our study was to retrospectively assess the incidence and the epidemiological trend of NIFTP in Mures county, Romania, five years after the introduction of this new entity. S138