ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 bladder neck. TUR of the prostate and bladder tumour was per- formed for the second time. Results: Histologically, TUR tissue revealed an ill-defined, infiltrative tumour composed of bland spindle cells within an abundant myxoid matrix interspersed with prominent vessels. Immunohistochemically, the spindle cells were positive for pro- gesterone receptor and negative for oestrogen receptor. The his- topathology was the same as that of the initial TUR specimen. The diagnosis of recurrent deep angiomyxoma of the bladder neck was confirmed. Conclusion: Though rare, deep angiomyxoma of the bladder neck should be considered as a cause of obstructive urinary symptoms. E-PS-24-026 Primary Ewing sarcoma/primitive neuroectodermal tumour of the kidney: a rare case report J. Baena-Del Valle*, D.M. Bertel-Rodriguez, M.A. Palau-Lazaro *Fundacion Santa Fe De Bogota, Universidad De Los Andes, Colombia Background & objectives: Ewing sarcoma/Primitive neuroectodermal tumour (ES/PNET) are undifferentiated tumours that originate from neuroectoderm. The occurrence in kidney is extremely rare (<1% of renal tumours), with less than 150 cases reported. We present a case of a young adult with a renal-ES/PNET. Methods: A 18-year-old woman presented with abdominal pain and haematuria. A computed tomography showed a 20 x 14 x 10 cm mass on the left kidney. A left radical nephrectomy was performed. Histology showed a small round cell malignant tumour with areas of necrosis and frequent mitosis. Results: Tumour cells were positive for CD99, synaptophysin and Fli-1. TLE-1, S100, AE1/AE3, EMA, CD34, desmin, CD45, GATA- 3, WT-1 and PAX-8 were negative. Ki-67 was 20%. Fluorescence in situ hybridization for the translocation EWS-FLI1/t(11;22) was negative. Due to the rarity of this tumour, neoplasms like blastemal-Wilms tumour, neuroblastoma, lymphoma, small cell carcinoma, rhabdoid tumour, desmoplastic small round cell tumour and synovial sarcoma, must to be excluded. Immunohistochemistry is helpful, but there could be immunophenotypic overlap that requires molecular testing. t(11;22) has been reported in approximately 70% of the kidney ES/ PNET, but other members of the ETS genes have less frequently been reported as variants, supporting the diagnosis in this case. Conclusion: The diagnosis of ES/PNET of the kidney depends on an integrated approach that includes histology, immunohisto- chemistry and molecular/genetic testing. Accuracy in the diagnosis is critical because compared to other primary renal tumours, ES/ PNET have a poor prognosis and an specific multimodal therapy. E-PS-24-027 Paraganglioma of the urinary bladder: two cases report J. Baena-Del Valle*, D.M. Bertel-Rodriguez, C.A. Medina-Mar- quez, M. Plata-Salazar, M.A. Palau-Lazaro *Fundacion Santa Fe De Bogota, Universidad De Los Andes, Colombia Background & objectives: Paragangliomas are rare, especially in the bladder. They represent 0.05% of bladder tumours and less than 1% of paragangliomas. Due to its rarity and symptomatic variability, preoperative diagnosis is often difficult. We present two cases of bladder paragangliomas in adults. Methods: 2 women, 54 and 59 years-old, presented with abdominal pain. Laboratory studies were normal. In both cases a cystoscopy revealed lesions less than 5 cm in the bladder wall, and a tran- surethral resection was performed. Histology showed solid nests and sheets of small granular cells with salt-and-pepper chromatin. Mitotic rate was low, and no necrosis or lymphovascular invasion was identified. Results: Tumour cells were positive for chromogranin, synapto- physin, CD56 and GATA-3. S100 highlighted the sustentacular cells, and Ki-67 was 2 - 5%. Keratin markers were negative. These findings were consistent with nonfunctional paragangliomas, and no recurrence has been reported so far. Bladder paragangliomas arise from the chromaffin cells of the bladder, explaining their intramural location. In nonfunctional cases the most important differential diagnosis is urothelial car- cinoma. Reactivity for CD56, chromogranin, synaptophysin, and S-100 are helpful in this distinction. Also, lack of reactivity with keratins, specially CK7, helps rule out other neuroendocrine neoplasms. Conclusion: Bladder paragangliomas may present clinical, radio- logical and pathological features similar to bladder cancer, with few cases reported in the literature. Early and correct identification is key to avoid misdiagnosis and overtreatment. Complete surgical removal of the lesion is considered the definitive treatment, either by transurethral resection or partial cystectomy, but long clinical and biological follow-up is warranted, as local recurrence can occur very late after the surgery. E-PS-24-028 Intermediate-risk solitary fibrous tumour of the prostate pre- senting as an intravesical prostatic protrusion: a case report J. Baena-Del Valle*, D.M. Bertel-Rodriguez, M. Plata-Salazar, M.A. Palau-Lazaro *Fundacion Santa Fe De Bogota, Universidad De Los Andes, Colombia Background & objectives: Solitary Fibrous Tumour (SFT) of the prostate is rare, with approximately 50 cases reported, 14 confirmed after the discovery of the NAD2-STAT6 fusion. We present a case of a middle-age-adult with a SFT presenting as an Intravesical Prostatic Protrusion (IPP). Methods: A 42-year-old man with a 5-year history of urinary reten- tion and suprapubic pain, was diagnosed with a benign prostatic hyperplasia, and treated with alpha-blockers. One year later he had persistence of the symptoms and an ultrasound revealed an enlarged prostate with a lesion protruding into the urinary bladder lumen (17 mm). A transurethral resection of the prostate was performed. Results: Microscopic examination showed a mesenchymal neo- plasm with variably cellular patternless pattern, cells were spin- dled to ovoid with uniform nuclei, branching staghorn vessels, and areas of fibrosis, without necrosis. 7 mitosis per mm2 were identified. Neoplastic cells were diffusely positive for STAT6 and CD34, and Ki-67 rate was 7%. A diagnosis of intermediate- risk SFT was made. Patient is currently being followed up with no evidence of recurrence or metastasis. Prostate-SFT mean age of presentation is 55 years, and most patients present with obstructive urinary symptoms. Presenting as an IPP is extremely unusual. Morphologic features are similar to extraprostatic SFTs and most of them are positive for STAT6, CD34, Bcl-2 and CD99. Conclusion: Many metastatic risk models have been developed; the most widely used, also validated in extra thoracic SFTs, includes mitosis, patient age, and tumour size to classify tumours into low, intermediate, and high risk. Recurrence and metastasis are rare. S356