ECP 2023 Abstracts

S372 Virchows Archiv (2023) 483 (Suppl 1):S1–S391 13 the TVT are often clinically mistaken with benign entities, which can result in delayed diagnosis. We will present a 3-case mesothelioma series. Methods: Histopathological findings and immunohistochemistry were used for diagnosis. For immunohistochemical markers 4μm thick sec- tions were taken from the blocks. Sectioned slides were kept in an oven at 65°C for 30 minutes, deparaffinized and tissues were adhered to the slides. The primary antibodies used in the study were in ready-to-use form and were automatically studied in the Ventana BenchMark Ultra device. Results: In our study, we examined three cases aged 60, 35 and 54 years, 2 of whom were known to have asbestos exposure, with com- plaints of mass in their testicles. Their hormone levels were normal in the laboratory. Histopathologically, it was observed that the tumour consisted of epithelioid-like cells with large, hyperchromatic nuclei, eosinophilic cytoplasm, some of which formed tubular, glandular or adenomatoid structures, some of which made nests. Immunohisto- chemically, the tumours were PAN-CK, calretinin, CK5/6, WT1 posi- tive, SALL4, PLAP, CD117, MELAN A and inhibin negative. The cases were diagnosed as malignant mesothelioma based on clinical information, asbestos exposure history, histopathological and immu- nohistochemical findings. Conclusion: Paratesticular mesothelioma is a rare tumour with nonspe- cific symptoms, clinical and radiological findings. There are a number of histological presentations to be aware of and pitfalls to be avoided, and caution should be exercised in the differential diagnosis. It is com- mon in middled-aged older men with asbestos exposure. Histologi- cally, it is often observed in epithelioid morphology. The cases will be presented with literature information because it is rarely seen in the paratesticular area. E-PS-24-021 Periampullary metastasis of renal cell carcinoma: a case report and review of the literature A. Dutta*, S.S. Nayak, V. Pradeep *Homi Bhabha Cancer Hospital and Research Centre, Visakhapatnam, India Background & objectives: Renal cell carcinoma (RCC) has potential to metastasize to almost any site and this may occur many years fol- lowing nephrectomy. The most common metastatic sites are lung, bone and liver. Periampullary metastasis of RCC is an extremely uncommon clinical scenario. Methods: A 49-year-old woman presented with fatigue, shortness of breath on exertion and melena of two months’ duration. She had undergone right nephrectomy for clear cell RCC 2 years ago. CECT scan showed an enhancing 4.6 x 4.2 cm periampullary lesion and two other lesions in body of pancreas. CT guided biopsy was done from the periampullary lesion. Results: Histological examination showed tissue cores infiltrated by a tumour arranged in sheets with interspersed thin walled blood vessels. The tumour cells were polygonal, had abundant amount of clear cytoplasm with well-defined cell border and round to oval, hyperchromatic nuclei. On immunohistochemistry, the tumour was diffusely positive for cytokeratin (AE1/AE3), PAX8 and focally positive for CD10. Final diagnosis was metastatic clear cell RCC. Thereafter, the patient was treated with palliative intent and started on sunitinib. The patient developed brain metastasis a month later and was offered whole brain radiotherapy. The patient eventually died after a month. Conclusion: Metastatic involvement of the periampullary region and other unusual sites should be suspected in any patient with a history of RCC. Optimal management is challenging because of high risk of relapse following treatment, leaving such cases with a very poor prognosis. E-PS-24-022 Sarcomatoid urothelial carcinoma on ureteral urothelial carcinoma in situ: a case report C. Esquina*, È. Iglesias Martínez, N. Santiago-Quispe, M.M. Buda, A. Sifre-Ruiz, A.M. Cordovilla-Moreno, M.J. De-Diego-Rivas *Clinical Department Unit of Pathological Anatomy, OSI Araba, Araba University Hospital; Bioaraba Health Research Institute, Vitoria- Gasteiz, Alava, Spain Background & objectives: Sarcomatoid urothelial carcinoma rep- resents 0.3% of urinary epithelial tumours. This is one of the most aggressive neoplasms of the urinary tract, developing in elderly patients and smokers. They are variants with possible heterologous differentia- tion with a more aggressive behaviour. Methods: We report a 61-year-old man with a history of pT1 uretheral carcinoma with tumour–like mass adhered to the psoas. Intraoperative biopsy was performed with a positive result for carcinoma. Right neph- roureterectomy was carried out with subsequent pathological study and literature review. Results: Gross examination of surgical specimen revealed marked thickening of the ureteral wall and the renal pelvis. The histopatho- logical study showed an urothelial carcinoma in situ and an infiltrating tumour with extension to the periureteral adipose tissue. This consisted of an atypical proliferation of spindle and epithelioid cells with exten- sive necrosis that was immunohistochemically positive for CKAE1/ AE3, p63, vimentin and focally for GATA-3. Was negative for S-100, desmin, CD45 and actine. The proliferative index Ki-67 was 90%. A definitive diagnosis of sarcomatoid urothelial carcinoma was made. Conclusion: Urothelial carcinoma exhibits multiple histological subtypes, including the sarcomatoid variant, characterized by areas indistinguishable from sarcoma. The differential diagnosis includes other entities, such as rhabdomyosarcoma, pleomorphic sarcoma and leiomyosarcoma. The presence of conventional urothelial carcinoma, as occurred in our case, and the compatible immunohistochemical study supports this diagnosis. In any case, even if there is a loss of expression of urothelial markers, priority should be given to histopathological findings after an exhaustive study. E-PS-24-023 Primary testicular lymphoma: a clinical, morphological and immu- nohistochemical characterisation of a long multicentre series B. Garzón*, J.d.B. Machuca Aguado, T. Cano, E. Montijano, G.A. Pastrana, Á. Gutiérrez *Juan Ramón Jiménez University Hospital, Huelva, Spain Background & objectives: Primary testicular lymphoma represents 1-2% of extranodal non-Hodgkin lymphomas, with diffuse large B-cell lymphoma (LBDC) being the most common histological subtype. Our objective is to make a clinical-pathological correlation of the diagnosed cases, comparing them with the literature. Methods: The series includes 25 cases, from three hospitals, diagnosed between 2005 and 2022 in orchiectomy specimens. Clinical data (age, laterality, stage, and follow-up) were collected. An immunohistochemi- cal study was carried out with CD20, CD79a, CD3, CD5, CD43, CD10, BCL2, BCL6, MUM-1, cyclin D1, granzyme B, C-MYC and Ki67. Results: All the patients debuted with a testicular whitish mass sized 7 to 10 cm that occupied the testicular parenchyma. N=25, age range from 35 to 89 years. 23 cases were diagnosed as DLBCL (8 germinal-centre immunophenotype, and 15 with activated immunophenotype, following Hans algorithm). At diagnosis, 9 were in stage I-II, 14 in stage III-IV and 2 unknown cases. 5 patients suffered CNS or testis relapse after treatment (all LGDLB). Survival at 5 years was 35%, being 75% in neoplasms limited to the testis at diagnosis, versus 17% in cases of disseminated disease at diagnosis. 36% (9/25) patients died from lymphoma. Of the rest, 24% (6/25) are in complete remission.