ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 capsule invasion was found in 5 cases. In one case, vascular invasion was reported. A total of 17cases could be classified as pMT according to the Pp. One patient developed pulmonary metastasis and local recurrence. Conclusion: Although the use of the term of pMT could reduce the psychological stress among patients and clinicians, it doesn’t seem to be of high interest in cases of concurrent ipsi or contralteral invasive papillary carcinoma since the patient’s prognosis is that of the invasive tumour. Further studies with large sample size and molecular analysis are also needed in order to definitively validate and generalize the use of Porto proposal. E-PS-08-004 Utility of intraoperative frozen section analysis on Bethesda category III-IV-V thyroid nodules and the effect of concurrent imprint cytology E. Hacihasanoglu*, F. Ozkan *Yeditepe University, Turkey Background & objectives: Bethesda category III-IV-V thyroid nodules represent therapeutic difficulty. This study aims to determine the utility of frozen section analysis (FS) on Bethesda category III- IV-V thyroid nodules and to investigate the effect of concurrent imprint cytology on diagnostic performance of FS. Methods: FS results and final diagnostic reports of all patients with Bethesda category III-IV-V nodule who underwent partial thyroidectomy or nodule resection with FS were scanned from hospital electronical database. Demographic information, size of the nodule and presence of concurrent imprint cytology were noted. Results: There were 81 patients fulfilling the criteria, with mean age of 43,5 years, female/male ratio of 3,2:1 and mean nodule size of 21 mm. In 20 cases, concurrent imprint cytology was performed and evaluated during FS. The overall sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of FS was 71,4%, 95%, 83,3% and 90,4%, respectively, with a diagnostic accuracy of 88,8%. When cases were separated as those with and without concurrent imprint cytology; sensitivity, specificity, PPV and NPV of FS with imprint cytology were 80%, 93,3%, 80% and 93,3%, respectively. For FS without imprint cytology; sensitivity, specificity, PPV and NPV were 68,7%, 95%, 83,3% and 90,4%, respectively. Conclusion: Bethesda category III-IV-V nodules have variable rates of malignancy and low concordance among pathologists, which causes difficulties in follow-up and treatment decisions. Use of FS is thought as a way to eliminate these difficulties. Overall, FS has low sensitivity for detecting malignancy in Bethesda category III-IV-V nodules. However, concurrent imprint cytology could help to increase the ability of FS to correctly identify malignancy. Larger studies regarding this aspect are needed. E-PS-08-006 Update regarding the role of PD-L1 in oncocytic thyroid lesions on cytological samples P. Tralongo*, M. Dell’Aquila, A. Granitto, M. Martini, M. Cura- tolo, V. Fiorentino, A. Pontecorvi, M. Raffaelli, L.M. Larocca, E.D. Rossi *Division of Anatomic Pathology and Histology - Fondazione Policlinico Universitario“Agostino Gemelli”-IRCCS, Rome, Italy Background & objectives: Few articles demonstrated a correlation between PD-L1 and papillary thyroid carcinoma (PTC) on thyroid fine needle aspiration cytology (FNAC). Its role in oncocytic thyroid lesions remains controversial, therefore we examined PD-L1 immunostaining in liquid-based cytology (LBC) of these lesions. Methods: From January 2019 to March 2021, 114 thyroid lesions diagnosed by FNAC as lesions with a predominant oncocytic com- ponent, were evaluated with PD-L1 immunostaining on both LBC and histology samples. FNAC cohort included 51 benign (B, negative controls), 4 Atypia of undetermined significance/Follicular lesions of undetermined significance (AUS/FLUS), 57 follicular lesions (FN/ SFN), and 2 suspicious for malignancy (SFM) cases. Results: Fifty-four cases (11B, 2 AUS/FLUS, 39 FN/SFN and 2 SFM) had histological follow-up: 1B case resulted as an oxyphilic nodule in Hashimoto Thyroiditis (HT), 10 B as goiters, 2 AUS/FLUSs as oncocytic adenomas (OAs); 39 FN/ SFNs included 27 OAs, 4 FA, and 8 oncocytic carcinoma (OC). The 2 SFMs were diagnosed as OAs. Increased plasma membrane and cytoplasmic PD-L1 expression were found in 47 LBC cases (41.2%). Among the histological series, 67.3% of OAs and 75 % of OC had PD-L1 expression, whilst nega- tive PD-L1 was found in oncocytic cells in HT. A positivity in >30% of the neoplastic cells was found in 72.9% of the cases including six OC. Conclusion: These data suggest that PD-L1 is expressed in onco- cytic thyroid lesions. While weak PD-L1 expression failed to dis- criminate benign from malignant lesions, OC demonstrated more intense cytoplasmic and membranous expression. E-PS-08-007 Papillary carcinoma of thyroid gland with CA 19-9 positivity. A case report E. Koniaris*, A. Mellou, E. Mortakis, M. Martzikou, G. Kafiri *Pathology department, General hospital of Athens "Hippokratio", Greece Background & objectives: Elevated levels of carbohydrate antigen 19-9 (CA 19-9), serologically and immunohistochemically, usually pre- sent with worse outcome and prognosis, especially in malignant cases. Usually, elevated levels of CA 19-9 have been associated mainly with malignancy and with medullary thyroid carcinomas. Methods: A 74-year-old female patient, presented with mul- tiple suspicious thyroid nodules measuring 0.5-6 cm, in both lobes. Microscopically the nodules were multiple foci of papillary carcinoma, sclerotic and oxyphil type, with severe perithyroidal extension, necrosis, perineural infiltration and calcifications. Two lymph nodes had metastases from the carcinoma. Results: Serological exams showed that the patient had increased levels of CA 19-9, thus indicating related immunohistochemical expression on the lesion. On IHC, it was confirmed a diffuse and widespread stain of CA 19-9 was confirmed. The lesions were also developed on the background of severe autoimmune thyroiditis. Conclusion: CA 19-9 might be of importance in predicting the prognostic outcome of a thyroid lesion, either benign (e.g., thyroiditis, Hashimoto thyroiditis and Graves disease) or malignant (e.g., papillary carcinoma). More specifically, increased expression of this antibody has been shown to demonstrate higher mortality rate than the control group. Some studies have correlated this phenotype with the tumour size, multifocality, local and distant metastasis and also RET mutation. E-PS-08-008 Clinico-morphologic characteristics of thyroid cancer with fol- licular morphology S249