The classification working group of the International Society of Urological Pathology consensus conference on renal neoplasia was in charge of making recommendations regarding additions and changes to the current World Health Organization Classification of Renal Tumors (2004). Members of the group performed an exhaustive literature review, assessed the results of the preconference survey and participated in the consensus conference discussion and polling activities. On the basis of the above inputs, there was consensus that 5 entities should be recognized as new distinct epithelial tumors within the classification system: tubulocystic renal cell carcinoma (RCC), acquired cystic disease-associated RCC, clear cell (tubulo) papillary RCC, the MiT family translocation RCCs (in particular t(6;11) RCC), and hereditary leiomyomatosis RCC syndrome-associated RCC. In addition, there are 3 rare carcinomas that were considered as emerging or provisional new entities: thyroid-like follicular RCC; succinate dehydrogenase B deficiency-associated RCC; and ALK translocation RCC. Further reports of these entities are required to better understand the nature and behavior of these highly unusual tumors. There were a number of new concepts and suggested modifications to the existing World Health Organization 2004 categories. Within the clear cell RCC group, it was agreed upon that multicystic clear cell RCC is best considered as a neoplasm of low malignant potential. There was agreement that subtyping of papillary RCC is of value and that the oncocytic variant of papillary RCC should not be considered as a distinct entity. The hybrid oncocytic chromophobe tumor, which is an indolent tumor that occurs in 3 settings, namely Birt-Hogg-Dubé Syndrome, renal oncocytosis, and as a sporadic neoplasm, was placed, for the time being, within the chromophobe RCC category. Recent advances related to collecting duct carcinoma, renal medullary carcinoma, and mucinous spindle cell and tubular RCC were elucidated. Outside of the epithelial category, advances in our understanding of angiomyolipoma, including the epithelioid and epithelial cystic variants, were considered. In addition, the apparent relationship between cystic nephroma and mixed epithelial and stromal tumor was discussed, with the consensus that these tumors form a spectrum of neoplasia. Finally, it was thought that the synovial sarcoma should be removed from the mixed epithelial and mesenchymal category and placed within the sarcoma group. The new classification is to be referred to as the International Society of Urological Pathology Vancouver Classification of Renal Neoplasia.

The International Society of Urological Pathology 2012 Consensus Conference made recommendations regarding classification, prognostic factors, staging, and immunohistochemical and molecular assessment of adult renal tumors. Issues relating to prognostic factors were coordinated by a workgroup who identified tumor morphotype, sarcomatoid/rhabdoid differentiation, tumor necrosis, grading, and microvascular invasion as potential prognostic parameters. There was consensus that the main morphotypes of renal cell carcinoma (RCC) were of prognostic significance, that subtyping of papillary RCC (types 1 and 2) provided additional prognostic information, and that clear cell tubulopapillary RCC was associated with a more favorable outcome. For tumors showing sarcomatoid or rhabdoid differentiation, there was consensus that a minimum proportion of tumor was not required for diagnostic purposes. It was also agreed upon that the underlying subtype of carcinoma should be reported. For sarcomatoid carcinoma, it was further agreed upon that if the underlying carcinoma subtype was absent the tumor should be classified as a grade 4 unclassified carcinoma with a sarcomatoid component. Tumor necrosis was considered to have prognostic significance, with assessment based on macroscopic and microscopic examination of the tumor. It was recommended that for clear cell RCC the amount of necrosis should be quantified. There was consensus that nucleolar prominence defined grades 1 to 3 of clear cell and papillary RCCs, whereas extreme nuclear pleomorphism or sarcomatoid and/or rhabdoid differentiation defined grade 4 tumors. It was agreed upon that chromophobe RCC should not be graded. There was consensus that microvascular invasion should not be included as a staging criterion for RCC.

Hereditary leiomyomatosis and renal cell carcinoma syndrome-associated renal cell carcinomas (RCC) are difficult to diagnose prospectively. We used immunohistochemistry (IHC) to identify fumarate hydratase (FH)-deficient tumors (defined as FH negative, 2-succinocysteine [2SC] positive) in cases diagnosed as "unclassified RCC, high grade or with papillary pattern," or "papillary RCC type 2," from multiple institutions. A total of 124 tumors (from 118 patients) were evaluated by IHC for FH and 2SC. An FH deficiency was found in 24/124 (19%) cases. An indeterminate result (only 1 marker abnormal) was found in 27/124 (22%) cases. In a tissue microarray of 776 RCCs of different types, only 2 (0.5%) tumors, initially considered papillary type 2, were FH deficient. FH mutations were found in 19/21 FH-deficient tumors (with confirmed germline mutations in 9 of 9 tumors in which germline status could be assessed) and in 1/26 FH-indeterminate tumors identified by IHC. No FH mutations were found in 2/21 FH-deficient RCCs, 25/26 FH-indeterminate RCCs, and 10/10 RCCs demonstrating FH expression by IHC. Patients with FH-deficient RCC had a median age of 44 years (range, 21 to 65 y). Average tumor size was 8.2 cm (range, 0.9 to 18 cm). FH-deficient RCCs were characterized by at least focal macronucleoli and demonstrated 2 or more growth patterns in 93% cases. Papillary was the most common (74%) and dominant (59%) pattern, whereas other common patterns included: solid (44%), tubulocystic (41%), cribriform (41%), and cystic (33%). At presentation, 57% were stage ≥pT3, 52% had positive nodes, and 19% had distant metastases. After a mean follow-up of 27 months (range, 1 to 114 mo), 39% of patients were dead of disease, and 26% had disease progression. We conclude that FH and 2SC are useful IHC ancillary tools, which allow recognition of FH-deficient RCC.

Both preemptive therapy and universal prophylaxis are used to prevent cytomegalovirus (CMV) disease after transplantation. Randomized trials comparing both strategies are sparse. Renal transplant recipients at risk for CMV (D+/R−, D+/R+, D−/R+) were randomized to 3-month prophylaxis with valacyclovir (2 g q.i.d., n = 34) or preemptive therapy with valganciclovir (900 mg b.i.d. for a minimum of 14 days, n = 36) for significant CMV DNAemia (≥2000 copies/mL by quantitative PCR in whole blood) assessed weekly for 16 weeks and at 5, 6, 9 and 12 months. The 12-month incidence of CMV DNAemia was higher in the preemptive group (92% vs. 59%, p < 0.001) while the incidence of CMV disease was not different (6% vs. 9%, p = 0.567). The onset of CMV DNAemia was delayed in the valacyclovir group (37 ± 22 vs. 187 ± 110 days, p < 0.001). Significantly higher rate of biopsy-proven acute rejection during 12 months was observed in the preemptive group (36% vs. 15%, p = 0.034). The average CMV-associated costs per patient were $5525 and $2629 in preemptive therapy and valacyclovir, respectively (p < 0.001). However, assuming the cost of $60 per PCR test, there was no difference in overall costs. In conclusion, preemptive valganciclovir therapy and valacyclovir prophylaxis are equally effective in the prevention of CMV disease after renal transplantation.

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Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome secondary to germline fumarate hydratase (FH) mutation presents with cutaneous and uterine leiomyomas, and a distinctive aggressive renal carcinoma. Identification of HLRCC patients presenting first with uterine leiomyomas may allow early intervention for renal carcinoma. We reviewed the morphology and immunohistochemical (IHC) findings in patients with uterine leiomyomas and confirmed or presumed HLRCC. IHC was also performed on a tissue microarray of unselected uterine leiomyomas and leiomyosarcomas. FH-deficient leiomyomas underwent Sanger and massively parallel sequencing on formalin-fixed paraffin-embedded tissue. All 5 patients with HLRCC had at least 1 FH-deficient leiomyoma: defined as completely negative FH staining with positive internal controls. One percent (12/1152) of unselected uterine leiomyomas but 0 of 88 leiomyosarcomas were FH deficient. FH-deficient leiomyoma patients were younger (42.7 vs. 48.8 y, P=0.024) and commonly demonstrated a distinctive hemangiopericytomatous vasculature. Other features reported to be associated with FH-deficient leiomyomas (hypercellularity, nuclear atypia, inclusion-like nucleoli, stromal edema) were inconstantly present. Somatic FH mutations were identified in 6 of 10 informative unselected FH-deficient leiomyomas. None of these mutations were found in the germline. We conclude that, while the great majority of patients with HLRCC will have FH-deficient leiomyomas, 1% of all uterine leiomyomas are FH deficient usually due to somatic inactivation. Although IHC screening for FH may have a role in confirming patients at high risk for hereditary disease before genetic testing, prospective identification of FH-deficient leiomyomas is of limited clinical benefit in screening unselected patients because of the relatively high incidence of somatic mutations.

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...

Renal medullary carcinomas (RMCs) and collecting duct carcinomas (CDCs) are rare subsets of lethal high-stage, high-grade distal nephron-related adenocarcinomas with a predilection for the renal medullary region. Recent findings have established an emerging group of fumarate hydratase (FH)-deficient tumors related to hereditary leiomyomatosis and renal cell carcinoma (HLRCC-RCCs) syndrome within this morphologic spectrum. Recently developed, reliable ancillary testing has enabled consistent separation between these tumor types. Here, we present the clinicopathologic features and differences in the morphologic patterns between RMC, CDC, and FH-deficient RCC in consequence of these recent developments. This study included a total of 100 cases classified using contemporary criteria and ancillary tests. Thirty-three RMCs (SMARCB1/INI1-deficient, hemoglobinopathy), 38 CDCs (SMARCB1/INI1-retained), and 29 RCCs defined by the FH-deficient phenotype (FH/2SC or FH/2SC with FH mutation, regardless of HLRCC syndromic stigmata/history) were selected. The spectrum of morphologic patterns was critically evaluated, and the differences between the morphologic patterns present in the 3 groups were analyzed statistically. Twenty-five percent of cases initially diagnosed as CDC were reclassified as FH-deficient RCC on the basis of our contemporary diagnostic approach. Among the different overlapping morphologic patterns, sieve-like/cribriform and reticular/yolk sac tumor-like patterns favored RMCs, whereas intracystic papillary and tubulocystic patterns favored FH-deficient RCC. The tubulopapillary pattern favored both CDCs and FH-deficient RCCs, and the multinodular infiltrating papillary pattern favored CDCs. Infiltrating glandular and solid sheets/cords/nested patterns were not statistically different among the 3 groups. Viral inclusion-like macronucleoli, considered as a hallmark of HLRCC-RCCs, were observed significantly more frequently in FH-deficient RCCs. Despite the overlapping morphology found among these clinically aggressive infiltrating high-grade adenocarcinomas of the kidney, reproducible differences in morphology emerged between these categories after rigorous characterization. Finally, we recommend that definitive diagnosis of CDC should only be made if RMC and FH-deficient RCC are excluded.