[Clinicopathological features of BAP1 mutated clear cell renal cell carcinoma].

Objective: To investigate the clinicopathological characteristics, immunophenotypes, molecular features, and differential diagnosis of BAP1 mutated clear cell renal cell carcinoma (CCRCC) for better understanding this entity. Methods: Clinical data, histological morphology, immunophenotypes and molecular characteristics of 18 BAP1 mutated CCRCC cases diagnosed at the Department of Pathology, the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China from January 2020 to December 2022 were analyzed. The patients were followed up. Results: There were 17 males and 1 female patients, aged from 39 to 72 years, with an average age of 56.3 years. Sixteen patients with primary CCRCC were followed up for an average of 24 months, 7 patients had metastases occurred from 4 to 22 months postoperatively. Thirteen of the 16 patients were alive at the time of the last follow-up while 3 patients died 12, 15, and 20 months after the surgery, respectively. One patient underwent retroperitoneal mass resection, but had lung metastasis 32 months after surgery. One case received cervical tumor resection and died at 22 months after the surgery. Characteristic CCRCC regions were identified in 11 of the 18 cases. The tumor cells were arranged in papillary, alveolar, and large nest patterns. Abundant lymphoid tissue, necrosis, and psammoma bodies were seen. Tumor cells showed abundant eosinophilic cytoplasm, and sometimes exhibited rhabdoid differentiation. Round eosinophilic globules were located in the cytoplasm and extracellular matrix. There were 9 cases with WHO/International Society of Urological Pathology grade 3, and 9 cases with grade 4. PAX8 (18/18), carbonic anhydrase 9 (CA9, 16/18), CD10 (18/18), and vimentin (18/18) were positive in the vast majority of tumors.TFE3 was expressed in 5 cases, with strong expression in only 1 case. Eighteen cases were all positive for P504s. Twelve cases harbored a BAP1 mutation combined with von Hippel-Lindau (VHL) mutation, and 2 cases had mutations in BAP1, VHL and PBRM1 simultaneously. SETD2 mutation was not found in any of the cases. Conclusions: BAP1 mutated CCRCC contained papillary, alveolar, and large nest patterns, eosinophilic cytoplasm, high-grade nucleoli, and collagen globules, with P504s positivity. In practical work, when encountering CCRCC containing these features, pathologists should consider the possibility of BAP1 mutations and conduct related molecular tests.

[Several key and difficult issues related to the grading of urothelial carcinoma of urinary bladder].

Grading and staging are the most important prognostic factors for both non-invasive and invasive urothelial carcinomas, and are also one of the most common difficulties encountered by pathologists in the daily diagnostic practice of urothelial carcinoma. Recently, the International Society of Urological Pathology organized a survey and questionnaire conference on various issues related to the diagnosis, grading, and staging of urothelial carcinoma, and ultimately formed a series of consensus opinions. This article briefly summarizes the consensus opinions of this series, and combines them with the current pathological diagnosis status of urothelial carcinoma in China. It briefly comments on how to apply this series of consensus opinions in the daily diagnostic practice of pathologists, deeply understand relevant diagnostic problems, and carry out relevant clinical pathological research to further solve problems.

[CK7+/CD117- low grade oncocytic tumor of the kidney: a clinicopathological analysis].

Objective: To investigate the clinicopathological, immunohistochemical and molecular characteristics of low grade oncocytic tumors (LOT) of the kidney with CK7+/CD117- staining pattern for enhancing the understanding of renal LOT. Methods: The clinical data, histological morphology and immunophenotypes of seven renal LOT cases diagnosed at the Department of Pathology, the First Affiliated Hospital, Zhejiang University School of Medicine from January 2017 to April 2021 were analyzed. The patients were followed up. Among the seven patients, five underwent high-throughput DNA targeted sequencing, and their molecular characteristics were analyzed. Results: The patients' age ranged 59-82 years, with an average of 70 years. There were 2 males and 5 females. The boundary of the tumor was clear. The tumor cells had homogeneous eosinophilic cytoplasm and round or oval nuclei, with a perinuclear halo. Small basophilic nucleoli were conspicuous (WHO/International Society of Urological Pathology grade 2). In the hypercellular areas, the tumor cells were mainly arranged in dense solid or nest. In the stroma, there were dilated veins, thick-walled arterioles and thick collagen fiber bundles that divided the cells into pseudonodules. In the sparsely cellular area, the tumor cells were arranged in the so-called "tissue culture" fashion. In addition, the stroma contained fresh hemorrhagic foci and lymphoid aggregates. High-throughput sequencing of 5 cases revealed that one case harbored mTOR gene missense mutation and another case harbored TSC1 frameshift mutation. Conclusions: LOT of the kidney is an indolent tumor with an overall good prognosis. Pathologists should not misdiagnose it as renal oncocytoma and chromophobe renal cell carcinoma.

[Atypical renal cysts: a clinicopathological and molecular analysis of six cases].

Objective: To investigate the clinicopathological characteristics and molecular genetics of atypical renal cysts. Methods: Six cases of atypical renal cysts were collected from Zhejiang Provincial People's Hospital, Hangzhou, China, between February 2014 and February 2019. The clinicopathological characteristics and disease progression were analyzed. The 3p deletion and trisomy of chromosomes 7 and 17 were detected using fluorescence in situ hybridization (FISH). Results: All of the 6 patients were male, aged 43-63 years (median: 52 years). Preoperative Bosniak classification showed 4 cases of grade Ⅱ, 1 case of grade Ⅰ and 1 of grade Ⅲ. Histologically, atypical renal cysts appeared as unilocular or multilocular cysts, lined by multilayered flattened or cuboidal-shaped clear or eosinophilic cells. They often showed short papillary projections, and lacked solid or nodular growth of the lesional cells within the wall or septa of the cysts. Histologically, these cysts could be classified into three categories: acquired cystic disease-associated renal cell carcinoma (ACKD-RCC)-like (3 cases), clear cell type (2 cases), and eosinophilic papillary type (1 case). Two cases of ACKD-RCC-like atypical renal cysts were accompanied by clear cell renal cell carcinomas. On immunohistochemical staining, ACKD-RCC-like atypical renal cysts were focally CK7+/AMACR+/CD57+, the clear-cell type atypical renal cysts were CK7+/CAⅨ+, and eosinophilic papillary type atypical renal cysts were CK7+/AMACR+. FISH analyses showed that one case of ACKD-RCC-like atypical renal cysts had trisomy 17 and one case of clear cell type had 3p deletion, while no signal abnormality was detected in the other cases. The six patients were followed up for 13 to 70 months (median: 27 months), and no evidence of renal cell carcinoma was noted. Conclusion: Atypical renal cysts are a group of lesions that are heterogeneous in clinical, histological and immunophenotypical and molecular genetic features. FISH analyses suggest that a subset of the cases may be precursors of currently known renal cell carcinomas. Extensively sampling and careful observation of the histological characteristics of the cyst wall are important for distinguishing atypical renal cysts from extensively cystic renal cell carcinomas.

[Clinicopathologic features of glomus tumor of the kidney].

Objective: To investigate the clinicopathologic and differential diagnostic features of glomus tumor of the kidney. Methods: Four cases of glomus tumor of the kidney were collected from the archives of Peking University Third Hospital, the Second Hospital of Tianjin Medical University, Ningbo Yinzhou Second Hospital and Zhejiang Provincial People's Hospital between January 2012 to June 2017; the clinical and radiologic features, histomorphology, immunohistochemistry, ultrastucture and prognosis were analyzed and the relevant literature was reviewed. Results: Patients consisted of 2 men and 2 women with ages ranging from 37 years to 66 years (mean 55 years). Three patients had history of hypertensive disease (grade Ⅱ, 3 to 10 years). The tumors measured in maximum diameter from 3.0 cm to 4.0 cm (mean 3.6 cm) and showed gray-white to yellow and tan on cut surface. Macroscopical examinations showed all tumors were circumscribed but non-encapsulated. Histologically, 1 tumor presented as glomus tumor with extensive myxoid change, 1 as cellular and solid pattern glomus tumor, 1 as glomangioma with focal myopericytoma-like pattern and 1 as symplastic glomus tumor with areas resembling myopericytoma. The tumor cells in two cases showed scant cytoplasm and uniform, bland-appearing nuclei without mitoses. In one case, the tumor cells were epithelioid with abundant eosinophilic cytoplasm and relatively well-defined cell borders. There was an increased mitosis of 4/50 HPF; however, no evidence of atypical mitosis or nuclear atypia was noted. In the symplastic glomus tumor the tumor cells showed frequently nuclear pleomorphism without mitoses. By immunohistochemistry, all tumors showed strong and diffuse reactivities to at least 3 of the 4 muscle-associated markers (SMA, h-Caldesmon, MSA and Calponin), 3 tumors strongly and diffusely expressed collagen Ⅳ, 2 expressed CD34 and 1 focally expressed desmin; whereas markers including epithelial, neuroendocrine, nephrogenic, melanoma-associated, STAT6, S-100 protein, CD117 and ß-catenin all were negative in all the 4 tumors. Ultrastuctural analysis was done in 2 cases and showed prominent cytoplasmic actin bundles and pericellular basement membrane, and lacking of rhomboid renin crystals in both tumors. The hypertension persisted after surgical resection for all the 3 patients with this medical history. Follow-up information (range: 6-64 months, mean: 44 months)showed that no evidence of local recurrence or distant metastasis was identified in all 4 patients. Conclusions: Glomus tumor rarely occurs in the kidney and usually has a good prognosis. Careful attention to its morphology with the judicious use of immunohistochemistry and ultrastuctural analysis can be helpful for its diagnosis and differential diagnosis.