ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 literature. We report a case of a young female with a kidney mass, highlighting the microscopic characteristics of this tumour. Methods: A 30-year-old female patient with an incidental tumour mass in her left kidney was admitted for surgical treatment. The abdominal computed tomography and MRI examinations revealed a well-defined heterogeneous enhancing lesion measuring 2.62 × 2.38 cm located in the peripheric medial zone of the left kidney. Radical nephrectomy with locoregional lymphadenectomy was performed and microscopic evaluation was requested. Results: The paraffin-embedded tissue demonstrated a nodular neo- plasm composed of monomorphic round cells with eosinophilic cyto- plasm and centrally located nuclei, admixed with delicate-branching vascular spaces and smooth muscle fibres. No evidence of increased mitotic index or necrosis was found. The neoplastic cells were positive for CD34, smooth muscle actin, desmin, calponin, CD117, and colla- gen IV in a characteristic pericellular pattern. In contrast, tumour cells were negative for Melan A, HMB-45, S100, synaptophysin, cytokeratin AE1/AE3, CD31, and CD57. The Ki-67 staining index was 1%. Peri- odic acid-Schiff (PAS) staining revealed well-defined cytoplasmatic membranes of the neoplastic cells. The morphological features and the immunohistochemical profile indicated a benign glomus tumour of the kidney, glomangiomyoma-subtype. Conclusion: Primary glomus tumours of the kidney are rare, and they can mimic other renal neoplasms radiologically. By adding another case to the literature, we emphasize the histological and immunohistochemical features of this entity. A long-term follow-up is recommended despite its benign nature. It would be wise to investigate such rare cases of sporadic glomangiomas arising in young patients for an oncogenic mutation (BRAF and KRAS mutations or NOTCH gene rearrangement), but further research in this field is needed. E-PS-24-004 Amphicrine carcinoma of the urinary bladder: a case report G.M. Pini*, G. Finzi, L. Nicolini, S. Gianazza, A. Coppola, E. Zaffuto, F. Dehò, S. Uccella *University of Insubria, Italy Background & objectives: Amphicrine carcinoma (AC) is a rare neoplasm with hybrid exocrine and neuroendocrine morphological, immunohistochemical and ultrastructural features. We present the case of an 82-year-old man which, to our knowledge, is the first report of an AC of the urinary bladder. Methods: In May 2018 an 82-year-old man presented with painless gross haematuria at Circolo Hospital, ASST-Sette Laghi, Varese (Italy). Trans-urethral resection of the bladder (TURB) showed endoscopic evidence of a mass involving the posterior vesical wall which was biopsied. The patient also underwent cystoprostatectomy. Results: TURB specimen revealed a muscolaris-propria- infiltrating neoplasia with tumoral necrosis, cytoplasmatic g ranular ity, extra- and intra-cellular Alcian+ mucins. I mmu n o h i s t o c h em i c a l p h e n o t y p e wa s a s f o l l ows : synaptophysin+, chromogranin+, INSM1+, MUC5AC+, MUC2+ (patchy), MUC6-, abnormal (hyper-expressed) p53, Rb1-, p16+. Proliferative index (Ki-67): 90%. The concomitant presence of dense-core neuroendocrine and exocrine mucinous vesicles within the same neoplastic cell was confirmed with the use of transmission electron microscope and with colloidal-gold ultrastructural immunocytochemistry. Final diagnosis was AC of the vesical bladder. Similar results were present in the cystoprostatectomy specimens which brought to a pT3b pN0 pathologic staging. The patient eventually died after 434 days from bioptical diag- nosis of AC for multiple systemic infections. Conclusion: We present the first reported case of bona fide AC of the urinary bladder. While the differential diagnosis with metastatic adenocarcinoma and urachal carcinoma is of paramount importance, recognizing the hybrid exocrine- neuroendocrine nature of these neoplasms is key with regard to the acquisition of further knowledge on this rare entity. E-PS-24-006 V600E BRAF mutation in Rosai-Dorfman disease with testis- brain localization N.P. Tenace*, M.G. Cangi, R. Lucianò, L. Pecciarini, G. Grassini, G. Magliacane, M. Ponzoni, C. Doglioni, M. Colecchia *Vita-Salute San Raffaele University, Milan, Italy Background & objectives: Rosai Dorfman disease (RDD) is a rare form of systemic non-Langerhans cell histiocytosis. RDD classical presentation is with lymphadenomegaly, but extranodal sites may be involved. We described the immunohistochemical and molecular pro- file of an unusual testicular/cerebral RDD. Methods: A 54-year-old male patient presented at San Raffaele Hospital with an unusual testicular enlargement and neurological alterations characterized by gait disorders, dysarthria, and dys- esthesia in the four limbs dating since a year. On MRI, a pontine mass was found, with PET enhancement, detected bilaterally in the testes and at the root of abdominal aortic arterial branches. Monolateral orchiectomy was performed. Results: On macroscopic examination, the testis appeared to be slightly increased in size with the presence of interspersed miliary-shaped yellowish formations in the parenchyma. Histologically, nodules of large, pale histiocytes (S-100+/ CD163+/CD68+/CD207-/CD1a-) with emperipolesis were observed. Diagnosis of Rosai-Dorfman disease, extranodal subtype, was made. Molecular analysis performed on testicular tissue detected V600E BRAF gene mutation; the same mutation was detected in cerebrospinal fluid. Conclusion: RDD usually has an indolent course, characterized by frequent spontaneous remission. RDD localization to the tes- ticular parenchyma is extremely rare and our case is the first with synchronous presentation to the central nervous system. The V600E BRAF gene mutation is extremely rare in RDD; it has been described till now only in brain RDD localizations. BRAF mutation in our case, besides relevant clinical opportunities, sug- gests a testis-brain axis for this form of RDD E-PS-24-007 Basaloid carcinoma of the bladder: is it a new variant with poor prognosis? Case report I. Elouarith*, K. Znati, A. Jahid, Z. Bernoussi, F. Zouaidia *Ibn Sina University Hospital Center, Morocco Background & objectives: Basaloid carcinoma is an exceptional vari- ant of squamous cell carcinoma of the bladder. We aim through this case, the 4th in the literature, to describe the pathological features of this entity and highlight its poor prognosis according to our experience. Methods: A 51-year-old patient consulted for haematuria with bladder mass on imaging. So, he underwent a cystprostatectomy. Histological study confirmed the diagnosis of basaloid squamous cell carcinoma of the bladder. The patient subsequently benefited from chemotherapy, but died after the third session. S350