ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 occurred in patients 15-66 years old (average=32, median=9), in femur (26,36.6%), proximal tibia (11,15.5%), distal radius (9,12.6%), pelvis, including sacrum (8,11.2%) and other bones (17,23.9% ), including a single multicentric case. Results: Out of 67 GCTBs, wherein H3F3G34W immunostaining worked, 55(82.1%) cases showed positive staining in the mononu- clear cells, including tumours with fibrous histiocytoma-like areas, sparing the osteoclast-like giant cells. The average percentage of tumour cells showing positive immunostaining was 69%, with 3+ staining intensity in 42/55(76.4%) cases and 2+ in 13(23.6%) GCTBs. All 4/4(100%) malignant GCTBs showed positive staining, including the mononuclear and pleomorphic/sarcomatous cells. Three(4.3%) cases developed metastasis(axillary nodes, mediasti- num and lung). All 3/3(100%) metastatic GCTBs showed positive immunostaining in the metastatic lesions. Out of seven post-den- osumab treated GCTBs, four showed no residual giant cells and lacked H3.3G34W immunostaining. None of the other 37 “giant cell-rich” lesions displayed H3.3G34W immunostaining. Conclusion: The diagnostic sensitivity of H3.3G34W for GCTB was 82.1% and specificity was 100%. The present study, constitut- ing one of the first reports from our country, further validates the value of H3.3G34W in differentiating GCTB, including metastatic and malignant type from its diagnostic mimics. Its utility in iden- tifying residual tumour cells in post-denosumab treated GCTBs is worth exploring. Funding: Intramural grant, Tata memorial Hospital, Parel, Mumbai OFP-04-009 COVID-19 placentitis in pregnant women may be complicated by foetal death P. Babál*, L. Krivošíková, I. Deckov, M. Ondrejka, P. Martanovic, P. Janega *Institute of Pathological Anatomy, Comenius University, Brati- slava, Slovakia Background & objectives: Dominant clinical manifestations of the SARS-CoV-2 infection are in the lungs, however, pathological consequences of COVID-19 in different organs have been docu- mented in multiple studies. Only limited data are available about the outcome of this infection in pregnant women. Methods: Two cases of intrauterine death of the foetus in mothers after overcoming COVID-19 with mild symptoms were studied in detail. Placentas hebd. 38 and 35, respectively, were nodular, hard- elastic, with whitish to dark pink areas affecting 70 – 80%. Autopsy of the babies was performed. No pathological abnormalities were grossly identified in either case. Results: Microscopic evaluation of the placental tissue revealed broad intervillous and perivillous deposits of fibrin with marked histiocytic infiltration, scant lymphocytes and focally with neutro- phils, especially in areas of forming infarctions. Inflammation of villi was not prominent. Immunohistochemistry and in-situ hybridi- zation proved the ongoing presence of syncytiotrophoblast infec- tion by the SARS-CoV-2 virus. This finding was also confirmed by the +PCR test from placental tissue samples. Histological evalu- ation of tissues of the foetuses showed only mild interstitial lym- phocytic infiltration in lungs and sporadic immunohistochemical and in-situ hybridization positivity of SARS-CoV-2 in individual cells in lungs and kidneys, which was also confirmed by the +PCR test in lung tissue samples. Conclusion: The two presented cases documented the development of placentitis caused by SARS-CoV-2 infection after uncomplicated COVID-19. This process is associated with massive deposition of intervillous fibrin and placental infarctions with consequent ischemia and death of the foetus. Although the vertical transfer of the infection was documented, the SARS-CoV-2 virus infection did not contribute to the foetal demise in the presented cases. This rare complication of pregnancy appears to be independent of the seriousness of COVID-19 clinical course in the mother. Funding: Supported by APVV grant PP-COVID-20-051. OFP-04-010 Histological and molecular features of placental and foetal tissues in pregnancies with SARS-CoV-2- positive mothers during second and third trimester: the Bergamo experience in vertical transmission D. Morotti*, L. Patane, M. Cadamuro, V. Poletti de Chaurand, M. Arosio, L. Goisis, G. Massazza, E. Rigoli, P. Tebaldi, A. Gianatti *Department of Pathology, Papa Giovanni XXIII Hospital, Italy Background & objectives: Intrauter ine transplacental transmission of SARS-CoV-2 to the foetus is rare but possible in infected pregnant women. According to WHO 2021 classification criteria, both stillborn and liveborn neonates appear to have the possibility to acquire transplacental COVID-19 infection prior to delivery. Methods: During the first pandemic wave, two Covid-19 posi- tive women delivered two positive babies at third trimester. In September 2021 a case of second trimester twin stillbirth have found positives to SarS-Cov-2 from an asymptomatic infected mother. All specimens collected were analysed by real time PCR, immunohistochemistry and in situ hybridization RNA in order to detect and to localize SARS-CoV-2. Results: All placentas showed unusual pathology abnormalities that include chronic histiocytic intervillositis with presence of CD68+ macrophages, syncytiotrophoblast necrosis and positiv- ity of the syncytiotrophoblast for SARS-CoV-2 antigen or RNA. Notably, Hofbauer cells do not resulted infected by viral particles as outlined by double staining for CD163+(marker for Hofbauer cells) and ISH for SARS-CoV-2 (spike protein) RNA. Foetal autopsies didn’t show any malformations. The lung of the first foetus only showed interstitial pneumonia features with vascular congestion and neutrophilic infiltrate. Viral genome sequenc- ing identified the lineage B.1.1 in two women who delivered in March 2020, while in the third positive woman, who aborted during the third pandemic wave, was detected B.1.36 lineage. Conclusion: We gave evidence that SARS-CoV-2 vertical trans- mission mother-foetus is possible also in second trimester of pregnancy and in asymptomatic pregnant women and can lead to severe morbidity. We found a specific histologic pattern in all infected placentas and our studies ruled out the pathogenic involvement of Hofbauer cells. Furthermore, as far as we know, it does not appear that different genetic variants of the virus affect its possible transplacental vertical transmission. OFP-04-011 Diagnostic value of ITS sequencing in mucormycosis – a retro- spective single-centre study M. Zacharias*, A. Thüringer, K. Kashofer, R. Krause, G. Gorkiewicz *Diagnostic and Research Institute of Pathology, Medical Univer- sity of Graz, Austria Background & objectives: Mucormycosis is a fast-progressing disease with a high mortality rate. Rapid and accurate diagnosis is of utmost importance, but microbiological culture may lack sen- sitivity. Molecular techniques are therefore increasingly recom- mended; however, real-world data about their value are still sparse. Methods: Between 2015 and 2022, we performed internal transcribed spacer (ITS) sequencing in 491 tissue and body S17