ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 therefore, control of digestive symptoms in patients with COVID- 19 is recommended. E-PS-13-015 Primary lymph node actinomycosis, a case report S. Mabrouk*, T. Tlili, Z. Lajmi, Y. Fejji, A. Ben Abdelkader, B. Sriha, M. Mokni *Department of pathology, Farhat Hached university hospital, Tunisia Background& objectives: Actinomycosis is a rare chronic bacterial infec- tion caused by Actinomyces species. It typically affects soft tissue of the cervicofacial region, pelvis and lungs. Primary involvement of lymph nodes is extremely uncommon. Only three cases have been reported so far. Methods: A 41-year-old man with unremarkable medical history presented with a 6-week history of painless cervical lump. Physical examination showed a mobile, non tender, left submandibular lymph node measuring 1.5 cm. The patient denied any history of recent dental extraction or oral manipulations. Neck ultrasound showed no other enlarged lymph nodes. An excisional lymph node biopsy was performed. Results: Grossly, the lymph node measured 1.3 cm in long axis. The cut surface was white yellow and showed no nodularity or necrosis. Histological examination revealed fibrous thickening of the capsule. Thick fibrous bands were also seen between the lym- phoid follicles, as well as rare small characteristic sulphur granules that were positive with Periodic acid Schiff and Grocott stains. Final cultures were positive for Actinomyces. The patient received long-term penicillin G therapy. Conclusion: Actinomyces is a commensal of oral cavity. After disruption of the oral mucosa, it typically spreads by direct destruction of tissue. Lymphatic spread leading to primary involvement of lymph nodes is extremely uncommon. Awareness of this rare misleading presentation is crucial to avoid erroneous diagnosis. Actinomycosis should be considered in case of persistent lymph node enlargement in patients with poor dental hygiene. Sulfur granules are highly suggestive but not pathognomonic of actinomycosis. Microbiologic examination is necessary for a definitive diagnosis. E-PS-13-016 The diagnosis of non-tuberculous mycobacterial infections on formalin fixed paraffin embedded tissues: a retrospective analysis M. Khaba*, L. Ndam, N. Makhado *Sefako Makgatho Health Sciences University, South Africa Background & objectives: The prevalence of nontuberculous myco- bacteria infection is increasing around the world with a negative impact on the health system. The histopathological features of mycobacterial tuberculosis and nontuberculous mycobacteria infection are indistin- guishable on tissue biopsy, hence the aim for this study. Methods: This was a retrospective study which consisted of all tissue biopsy from patients suspicious for mycobacterial infection which were diagnosed with granulomatous inflammation from 2018 - 2020. These cases were tested using GenoType Mycobac- terium CM/AS assay (Hain Life Sciences; Germany, Nehren) to identify mycobacterial species. Results: A total of 25 cases comprised the study cohort and con- sisted of 18 females and 7 males with mean age of 37.78 years. HIV seropositive was noted in 32% (8/25) of the cases. Biopsy sites were as follows: lymph nodes 52% (13/25), pleura 20% (5/25), breast 12% (3/25), testis and stomach 8% each (2/25). Microscopically, all the cases showed necrotizing granulomatous inflammation. Ziehl Neelsen staining was positive in 8% (2/25) of the cases. The identified mycobacterial species were as follows: M. fortuitum (76%), M. avium (4%), M. interjectum (4%), Myco- bacterium. spp (16%). Conclusion: Genotyping of mycobacterial species is very impor- tant as the morphological features and Ziehl Neelsen staining were unhelpful to distinguish between mycobacterial tuberculosis and non-tuberculosis mycobacterial infection in this study. Definite diagnosis of mycobacterial infection on paraffin embedded tissue sections has important treatment implication for the patient. E-PS-13-017 Immunohistochemistry (IHC) for SARS-CoV2 - identification of monoclonal antibodies (mAbs) to nucleoprotein, S1- and S2-spike protein subunits and analysis of differential expres- sion of viral proteins in formalin-fixed paraffin-embedded specimens A. Jungbluth*, W. Travis, D. Frosina, J. Bagha, E. Hernandez, J. Sauter, M. Szabolcs *Memorial Sloan Kettering Cancer Center, USA Background & objectives: Proper detection of the viral proteins to SARS-CoV2 is mandatory for the morphological assessment of Covid19-induced pathologic changes. We identified commercially available mAbs to NP, S1, and S2 SARS-CoV2 respectively. A com- parative expression analysis was performed in virally infected tissue. Methods: A tissue-independent testing method for screening mAbs was employed using HEK293 cells transfected with the various viral proteins). FFPE pellets of HEK293 cells transfected with NP, S1 and S2 proteins were generated and used for mAbs testing/selec- tion. MAbs were then tested on SARS-CoV2+ve specimens, and in-situ expression of NP, S1, S2 proteins was compared. Results: Several commercial anti-SARS-CoV2 mAbs were con- secutively tested. Most antibodies did not work in IHC and/or gen- erated unspecific reactivity with various viral proteins. Only 3/10 mAbs proved useful for IHC in FFPE material. The reagents were: mAb 001 (anti-NP; SinoBiological) mAb 1A9 (anti-S2; GeneTex), and mAb 1035206 (Anti-S1; Novus). All mAbs gave also strong and consistent staining in FFPE tissue. Comparative immunostain- ing in lung autopsy cases showed that NP was most abundant while S1/S2 proteins were less prevalent. Difference was less striking in biopsies. More congruent expression of viral proteins was seen in placenta. Overall the NP was most widely present, while S1 and S2 showed a much more restricted expression Conclusion: HEK-293 cells transfected with viral proteins are an excellent way to test anti SARS-CoV2 mAbs for specificity and suitability. Most commercial mAbs show unspecific staining and are unsuitable for IHC. Moreover, there are different expres- sion patterns for NP, versus S1 and S2 proteins in infected human specimens. Consequently, presence of SARS-CoV2 proteins may depend on which viral protein was analysed. Therefore, morpho- logical studies of Covid19-related changes are impacted by which viral protein was analysed and may have limited comparability. E-PS-13-018 Analysis of pathological changes in spontaneous abortions in pregnant women with IgM positive for Dengue, Chikungunya, Zika or with positive treponemal test for syphilis D. Nunes*, B. Sobreira Camilo Soares, A.R. Jucá Parente, J. Car- neiro Melo, A.N. Melo Cavalcante, R.L. Freitas de Almeida, G. Silva Bastos, R.V. Vasconcelos de Paula, P. Jorge Pires Viana, L.M. S297