ECP 2022 Abstract Book

Virchows Archiv (2022) 481 (Suppl 1):S1–S364 13 Complete surgical resection is the treatment of choice and the most important prognostic factor. Chemotherapy and/or radiotherapy should be considered as palliative treatment. E-PS-24-029 Spontaneous regression of primary renal cell carcinoma: two cases S. Kılar Kösemen*, G. Gümrükçü *Haydarpasa Numune Training and Research Hospital, Turkey Background & objectives: Renal cell carcinoma (RCC) accounts for 2% of all new cancer cases in adults. Although spontaneous regression in primary RCC and metastases is rare, it is a well-known phenomenon. Methods: We report two cases of spontaneous regression of RCC in an 81-year-old and a 70-year-old male that underwent partial nephrectomy for an incidental kidney mass. The entire lesion was sampled in both cases, and immunohistochemistry studies were performed. Results: In the first case, a 4.5 cm haemorrhagic and necrotic mass separated from the parenchyma by a smooth thick fibrous capsule was observed macroscopically. No viable tumour cells were observed in H&E sections and immunohistochemistry studies. The case was evaluated as RCC showing spontaneous regression. Sub- type couldn’t be determined. In the second case, a 2.5 cm, off-white, hard tumoral mass surrounded by thin parenchyma was observed macroscopically. Tubular structures formed by cells with clear cytoplasm, which can hardly be distinguished between hyalinized and calcified areas, were seen in H&E sections. Cytoplasmic membranous staining with CA-IX was demonstrated by immunohistochemistry. The case was diagnosed as RCC-clear cell type showing spontaneous regression. Conclusion: Spontaneous regression was reported in partial or complete RCC metastases from time to time. However, spontaneous regression of primary RCC is extremely rare. Only 4 cases have been reported in the literature. Regressed renal cell carcinomas should be considered in the differential diagnosis of solitary renal lesions and the entire lesion should be sampled. E-PS-24-030 Tubulocystic renal cell carcinoma – a malignant entity with bland features and good prognosis G. Fontinha*, R. Almeida, J. Gama, V. Sousa *Centro Hospitalar e Universitario de Coimbra, Department of Pathology, Portugal Background & objectives: The differential diagnosis for multicystic renal neoplasms includes adult cystic nephroma and the recently described multilocular cystic renal neoplasm of low malignant potential and tubulocystic renal cell carcinoma. The latter is an indolent entity with few reported cases. Methods: In this case report we present the case of an otherwise healthy 66-year-old male with an incidental finding of a Bosniak IIF-III cystic renal lesion with 2.8 cm. The growing of the mass in subsequent imaging studies prompted a partial left nephrectomy in this asymptomatic patient. Results: The gross examination showed a well circumscribed and completely excised multilocular cystic lesion with 3x2.6x0.9 cm. Histology revealed multiple cysts lined by a single layer of hobnail cells with conspicuous nucleoli at 100x magnification and eosino- philic cytoplasm. No clear cell type of lining, areas of epithelial proliferation or intracystic structures were present. In the cyst walls there were tubular structures lined by flattened to cuboidal cell with no to little atypia. Immunochemical CD10, CK7, CK19, AMACR stains were positive in neoplastic cells while CD117, car- bonic anhydrase IX and oestrogen and progesterone receptors were negative. Ki67 stain was positive in 1% of tumour cells. There was no colloidal iron staining. Conclusion: While having good prognosis in most cases the exclu- sion of non-malignant entities is warranted since recurrence and metastasis have been reported. This case underlines the incidental diagnostic aspect of this carcinoma which is assonant with its indo- lent course. Recent studies have showed the tubulocystic renal cell carcinoma distinct genomic profile, but more is to be done in order to assert the prognosis of pure tubulocystic renal cell carcinoma and when in association to other entities. E-PS-24-031 Basal cell carcinoma of Prostate with MSMB-NCOA4 fusion and a probable basal cell carcinoma in-situ: case report A.C. Loya*, V. Pedersen, K.S. Petersen, O. Østrup, K. Brasso *Rigshospitalet, Denmark Background & objectives: Basal cell carcinomas of prostate (BCCP) is very rare. Lower urinary tract symptoms, normal PSA & rarity of tumour renders diagnosis difficult. This is an attempt to describe a non-existent Basal cell carcinoma in situ (BCCIS) for first time ever. Methods: Prostatectomy material from a 74-old man was evaluated histologically, immunohistochemically and molecular studies (Archer FusionPlex Solid Tumour panel, whole genome sequencing & Single Nucleotide Polymorphism Arrays). Needle biopsies of abdominal wall metastasis and prostatic needle biopsy performed in 2005 were also evaluated. Results: Histology revealed a diffusely infiltrative tumour with solid growth pattern and glandular structures representing BCCIS. Tumour cells were positive for P40/P63/CK5/ & Vimentin. PSA/NKX 3,1/CK7/ CK20/GATA3/ & Uroplakin 2 were negative. A diagnosis of BCCP was rendered. Additionally, the glandular structures were seen 2-lay- ered, the adluminal NKX 3,1 & PSA positive single cell layer of normal cubical cells and abluminal broader neoplastic cell layer positive for basal cell markers (Figures 3 and 4). These glands with prominent bilayering, noninfiltrative character, and a stiff basement membrane highlights a probable “Basal carcinoma in situ (BCCIS). Molecular examination detected MSMB-NCOA4 fusion. Patient had metastasis to abdominal wall 8 months later and showed similar features. Conclusion: BCCP is an aggressive type of prostate cancer challeng- ing to diagnose based on routine protocols. This results in delayed diagnosis & treatment and thus poorer prognosis. Patients with this subtype of prostate cancer need appropriately designed, and maybe a totally different follow-up regimen independent of PSA, as it’s of no use in BCCP patients. Finally, diagnosis of BCCIS, if agreed upon, needs to be studied in a larger cohort to justify its existence and its role as a precursor lesion. E-PS-24-032 Primary urothelial carcinoma of the prostate. Case report and review of literature L. Berdica*, T. Bushati, A. Ndoja, E. Sukaj *American Hospital, Albania Background & objectives: Primary urothelial carcinoma of the pros- tate is a very rare tumour accounting < 2 % of prostatic neoplasia. It has a poor prognosis even with in-situ disease only and 20% have distant metastases, commonly to bone, lung, liver. S357