The microphthalmia transcription factor/transcription factor E (TFE)-family translocation renal cell carcinomas bear specific translocations that result in overexpression of TFE3 or TFEB. TFE3 fusion gene product overexpression occurs as consequence of different translocations involving chromosome Xp11.2, whereas TFEB overexpression is the result of the specific translocation t(6;11)(p21;q12), which fuses the Alpha gene to TFEB. Both TFE3 and TFEB are closely related members of the microphthalmia transcription factor/TFE-family, which also includes TFEC and microphthalmia transcription factor. These transcription factors have overlapping transcriptional targets. Overexpression of microphthalmia transcription factor has been shown to mediate the expression of cathepsin-K in osteoclasts. We hypothesize that the overexpression of the related TFE3 fusion proteins and TFEB in translocation renal cell carcinomas may have the same effect. We studied cathepsin-K in 17 cytogenetically confirmed microphthalmia transcription factor/TFE-family translocation renal cell carcinomas. Seven cases showed a t(6;11)(p21;q12), ten cases showed translocations involving Xp11.2; five cases t(X;1)(p11;q21) resulting in a PRCC-TFE3 gene fusion; three cases t(X;1)(p11;p34) resulting in a PSF-TFE3 gene fusion, one t(X;17)(p11;q25) resulting in an ASPL-TFE3 gene fusion, and one t(X;3)(p11;q23) with an unknown TFE3 gene fusion. As control we analyzed cathepsin-K in 210 clear cell, 40 papillary, 25 chromophobe renal cell carcinomas and 30 oncocytomas. All seven TFEB translocation renal cell carcinomas were labeled for cathepsin-K. Among the cytogenetically confirmed TFE3 translocation renal cell carcinomas, 6 out of 10 were positive. None of the other renal neoplasms expressed cathepsin-K. We conclude the following: (1) cathepsin-K is consistently and strongly expressed in TFEB translocation renal cell carcinomas and in 6 of 10 TFE3 translocation renal cell carcinomas. (2) Cathepsin-K immunolabeling in both TFE3 and TFEB translocation renal cell carcinomas distinguishes these neoplasms from the more common adult renal cell carcinomas, and may be a specific marker of these neoplasms. (3) These results further support the concept that the overexpression of TFE3 or TFEB in these neoplasms activates the expression of genes normally regulated by microphthalmia transcription factor in other cell types. Keywords: cathepsin-K; TFE3; TFEB; translocation; renal cell carcinoma; immunohistochemistryThe recently described microphthalmia transcription factor/transcription factor E (MiTF/TFE) family translocation renal cell carcinomas comprise the majority of pediatric renal cell carcinomas but also occur in adults. MiTF/TFE family translocation renal cell carcinomas are characterized by specific chromosome aberrations involving the genes transcription factor E3 (TFE3) and transcription factor EB (TFEB). The TFE3 transcription factor gene maps to chromosomal region Xp11.2, whereas the TFEB transcription factor gene maps to chromosome 6p21. 1,2 Several disti...

We have demonstrated the impact of PI3K/Akt/mTOR alteration on the biological behaviour of bladder tumours. Proper immunohistochemical examination of the PI3K/Akt/mTOR pathway can provide useful prognostic information, and the findings may represent an additional therapeutic avenue in the treatment of bladder cancers.

KIT (CD117), a tyrosine kinase receptor, has not been widely studied in epithelial tumours. In a systematic immunohistochemical survey of KIT expression on tissue arrays incorporating 671 cases, it was found that thymic carcinomas frequently express KIT. Twenty-two thymic carcinomas, 110 thymomas, and 16 non-neoplastic thymus glands were retrieved for further analyses. Immunohistochemically, 19 (86%) thymic carcinomas revealed heterogeneous to diffuse membranous positivity, whereas no thymomas or normal thymus glands contained positive epithelial cells. Using reverse transcriptase-polymerase chain reaction (RT-PCR), c-kit transcripts could be demonstrated in all immunohistochemically positive cases. PCR amplification and direct sequencing of the c-kit juxtamembrane domains (exons 9 and 11) and tyrosine kinase domain (exons 13 and 17) were also performed on the thymic carcinomas but mutations were not found. Some non-thymic epithelial tumours showed frequent KIT expression including adenoid cystic carcinomas of the salivary gland (100% positive), chromophobe renal cell carcinomas (94%), renal oncocytomas (67%), and neuroendocrine tumours (34%). Other carcinomas were infrequently immunoreactive for KIT. The findings of this study suggest that KIT is involved in the pathogenesis of thymic carcinomas. The overexpression of KIT in thymic carcinomas has potential diagnostic utility in differentiating these tumours from thymomas and carcinomas arising from other sites, which express KIT infrequently.

To verify prognostic significance of the 2004 World Health Organization (WHO)/International Society of Urological Pathology (ISUP) grading systems, we retrospectively studied the tumors of 1,515 patients who underwent transurethral resection of primary non-muscle-invasive urothelial tumors (pTa, 1,006 patients; pT1, 509 patients) confined to the bladder. Cases were classified according to the 2004 WHO/ISUP systems as 212 cases of papillary urothelial neoplasm of low malignant potential (PUNLMP), 706 low-grade papillary urothelial carcinomas (LPUCs), and 597 high-grade papillary urothelial carcinomas (HPUCs). PUNLMP showed the statistically significantly lowest recurrence cumulative incidence compared with the other tumor types. There were significant differences and trends for higher progression and cancer-specific mortality cumulative incidence in the following order: PUNLMP, LPUC, pTa HPUC, and pT1 HPUC. No differences of progression and cancer-specific mortality cumulative incidence were found between pTa and pT1 LPUC. Our study validates the usefulness of the 2004 WHO/ISUP system to classify urothelial tumors into prognostically distinct categories that would contribute to the design of therapeutic and monitoring strategies for patients with non-muscle-invasive bladder urothelial tumors.

The Gleason score is the most important prognostic marker for prostate cancer patients, but it suffers from significant observer variability. Artificial intelligence (AI) systems based on deep learning can achieve pathologist-level performance at Gleason grading. However, the performance of such systems can degrade in the presence of artifacts, foreign tissue, or other anomalies. Pathologists integrating their expertise with feedback from an AI system could result in a synergy that outperforms both the individual pathologist and the system. Despite the hype around AI assistance, existing literature on this topic within the pathology domain is limited. We investigated the value of AI assistance for grading prostate biopsies. A panel of 14 observers graded 160 biopsies with and without AI assistance. Using AI, the agreement of the panel with an expert reference standard increased significantly (quadratically weighted Cohen's kappa, 0.799 vs. 0.872; p = 0.019). On an external validation set of 87 cases, the panel showed a significant increase in agreement with a panel of international experts in prostate pathology (quadratically weighted Cohen's kappa, 0.733 vs. 0.786; p = 0.003). In both experiments, on a grouplevel, AI-assisted pathologists outperformed the unassisted pathologists and the standalone AI system. Our results show the potential of AI systems for Gleason grading, but more importantly, show the benefits of pathologist-AI synergy. Members of the ISUP Pathology Imagebase Expert Panel are listed below Acknowledgements.