ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 she expectorated massive sputum which keeps the dendritic shape like a bronchus. The histological examination of the sputum demonstrated adenocarcinoma cell clusters with fibrin formation. Immunohistochemically, CD4- or CD8-positive, tumour-infiltrating lymphocytes (TILs) were observed in the clusters of cancer cells as well as around them. The pulmonary adenocarcinoma cells showed immuno-expressions of PD-L1 and TTF-1. After one cycle of pembrolizumab, the symptoms improved, and chest radiography showed remarkable remission. Conclusion: To our knowledge, this is the first report eliciting the presence of intratumoral lymphocytes within the pulmonary tissues at the maximal timing of pseudoprogression. Notably, it was hard to distinguish pseudoprogression from hyper-progression because of the huge infiltrative shadow and exacerbating respiratory symptoms. Our current case suggested that progressive exacerbation within 4 weeks from the initiation of anti-PD-1 antibody displays the possibility of pseudoprogression, and the radiographic entity of pulmonary exacerbation could be explained by the presence of TILs. Funding: Tomonori Kawasaki is supported by Grants-in-Aid for Scientific Research (No. 21K06910 and No. 20K08131) from the Japanese Ministry of Education, Culture, Sports, Science and Technology and the National Hospital Organization (NHO) Grant (H29-NHO-01). E-PS-21-002 Uncommon primary pleural mesenchymal tumours: study of seven cases M. Garcia Martos*, C.M. Vieru, Y. Gómez Navarro, A. Panizo Santos *Hospital General Universitario Gregorio Marañón, Spain Background & objectives: Primary pleural tumours are uncommon but there is a wide variety of them, both benign and malignant, whose accurate diagnosis is very important. This study aimed to review the cases of mesenchymal pleural tumours in two Spanish institutions. Methods: We searched in two major hospitals for cases of uncom- mon primary pleural mesenchymal neoplasms over a period of 10 years (2012-2022). Seven cases (3 male and 4 female) were found, with a mean age of 57 years: two benign (schwannoma) and five malignant tumours (4 synovial sarcomas and 1 angiomatoid fibrous histiocytoma). We analysed clinical, histopathological, immunophenotypic and molecular features. Results: Schwannomas were incidental findings and malignant tumours symptomology were chest pain and dyspnea. Imaging studies of schwannomas and angiomatoid fibrous histiocytoma showed pleural confined tumours, whereas two out of four synovial sarcomas were poorly defined pleuropulmonary pseudocyst masses. Grossly, the latter, were lesions with cystic change, calcification and necrosis. Histologically, benign morphology and S100 posi- tive helped schwannomas diagnoses. On the other hand, synovial sarcomas consisted of dense fascicles of monomorphic spindle cell without epithelial component, all of them positive for CD99, two of them partially for EMA and Bcl2 and 1 positive for TLE-1. FISH studies showed SS78-SSX fusion in synovial sarcomas and EWSR1 gene rearrangement in angiomatoid fibrous histiocytoma. Conclusion: Primary pleural mesenchymal neoplasms are uncom- mon. It is important to recognize, as long as its prognosis and ther- apy could be different from the one of the most common neoplasms of the pleura, metastatic cancers and diffuse malignant mesothe- lioma. A pleural spindle cell neoplasm has a broad differential diagnosis, and although immunostaining and molecular advances are helpful, the knowledge of these rare lesions and its morphol- ogy together with clinical correlation, continue to be the key issue. E-PS-21-003 Thymomas sub-classification – WHO 5th classification application J. Madeira*, V. Almeida, V. Sousa, L. Carvalho *Centro Hospitalar e Universitário, Portugal Background & objectives: Thymomas are indolent neoplasias with an incidence of 1.7 cases/million in Europe and surgery is the gold standard for resectable disease. WHO 5th edition corroborates wide tumoral sampling for searching patterns, as well as surgical margins invasion evaluation. Methods: We present a Portuguese case series of resectable thy- momas concerning surgical biopsies/resections between 2016 and 2020, reviewed and updated according to WHO 5th edition classification. All cases were staged according to current rec- ommendations. Statistical analysis was performed to examine contingency tables and compare medians between groups. Results: Our sample comprises 48 thymomas corresponding to 25 women and 23 men; patients’ median age at diagnosis was 65-years-old. In this series, 33 thymomas were in stage I by AJCC, 10 of which showed transcapsular microscopic invasion (Masaoka stage II); 45 cases (93.8%) were staged pT1a, and 3 patients presented lung invasion (pT3). AB thymoma was the most prevalent histopathologic subtype, accounting for 31.3% of all cases, followed by predominantly B1 thymomas (27.1%). Commonly it was possible to recognize at least two patterns in each tumour, even observed in the same slide, depending on the tumoral sampling. Conclusion: Surgical resection status was the most important pre- dictor of outcome, achieved in 45 cases (93,8%); 2 cases were R1 and one specimen could not be evaluated due to extensive fragmentation. Median age of 65-years-old was observed, higher than 58-years-old reported in literature. All subtypes frequencies were within published data ranges. Masaoka staging is still the most widely accepted system for clinicians, requiring further studies to establish prognosis impact. Surgical margins status registries were the most important prognostic feature. E-PS-21-004 Idiopathic lymphoid interstitial pneumonia misdiagnosed as lung tuberculosis. Case report. M. Mnikhovich, A. Romanov*, L. Erofeeva *Central Pathology Laboratory, Research Institute of Human Morphology, Russia Background & objectives: Idiopathic lymphoid interstitial pneumonia is an interstitial lung disease not associated with autoimmune diseases (Sjogren’s syndrome, rheumatoid arthritis) or infections (HIV) unlike typical LIP. We present a case of ILIP, misdiagnosed as tuberculosis, in a young woman, 23 years old. Methods: A case of ILIP is presented in a 23-year-old female patient who was initially diagnosed with pulmonary tuberculosis. CT showed chronic cavity formation in the first and second segments of the left lung. Resection of the corresponding segments of the lung was performed, followed by grossing and microscopic examinations. S329