Expanding the spectrum of ALK-rearranged renal cell carcinomas in children: Identification of a novel HOOK1-ALK fusion transcript

ALK-Rearranged Renal Cell Carcinoma: A Multi-Institutional Study of 9 Cases With Expanding the Morphologic and Molecular Genetic Spectrum

ALK-rearranged renal cell carcinoma (ALK-RCC) is rare, molecularly defined RCC subtype in the recently published fifth edition of World Health Organization classification of tumors. In this study, we described 9 ALK-RCCs from a clinicopathologic, immunohistochemical, and molecular genetic aspect, supporting and extending upon the observations by previous studies regarding this rare subgroup of RCC. There were 6 male and 3 female patients with ages ranging from 14 to 59 years (mean, 34.4 years). None of the patients had sickle cell trait. The diagnosis was based on radical or partial nephrectomy specimen for 8 patients and on biopsy specimen for 1. Tumor size ranged from 2.5 to 7.2 cm (mean, 2.8 cm). Follow-up was available for 6 of 9 patients (6-36 months); 5 had no tumor recurrence or metastasis and 1 developed lung metastasis at 24 months. The patient was subsequently treated with resection of the metastatic tumor followed by crizotinib-targeted therapy, and he was alive without tumor 12 months later. Histologically, the tumors showed a mixed growth of multiple patterns, including papillary, solid, tubular, tubulocystic, cribriform, and corded, often set in a mucinous background. The neoplastic cells had predominantly eosinophilic cytoplasm. Focally, clear cytoplasm with polarized nuclei and subnuclear vacuoles (n = 1), and pale foamy cytoplasm (n = 1) were observed on the tumor cells. The biopsied tumor showed solid growth of elongated tubules merging with bland spindle cells. Other common and uncommon features included psammomatous microcalcifications (n = 5), rhabdoid cells (n = 4), prominent intracytoplasmic vacuoles (n = 4), prominent chronic inflammatory infiltrate (n = 3), signet ring cell morphology (n = 2), and pleomorphic cells (n = 2). By immunohistochemistry, all 9 tumors were diffusely positive for ALK(5A4) and 4 of 8 tested cases showed reactivity for TFE3 protein. By fluorescence in situ hybridization analysis, ALK rearrangement was identified in all the 9 tumors; none of the tested tumors harbored TFE3 rearrangement (0/4) or gains of chromosomes 7 and 17 (0/3). ALK fusion partners were identified by RNA-sequencing in all 8 cases analyzed, including EML4 (n = 2), STRN (n = 1), TPM3 (n = 1), KIF5B (n = 1), HOOK1 (n = 1), SLIT1 (n = 1), and TPM1(3' UTR) (n = 1). Our study further expands the morphologic and molecular genetic spectrum of ALK-RCC.

Update on Selected High-grade Renal Cell Carcinomas of the Kidney: FH-deficient, ALK-rearranged, and Medullary Carcinomas

High-grade renal cell carcinoma (RCC), often diagnosed at advanced stages, significantly contributes to renal cancer-related mortality. This review explores the progress in understanding specific subtypes of high-grade RCC, namely fumarate hydratase (FH)-deficient RCC, anaplastic lymphoma kinase (ALK)-rearranged RCC, and SMARCB1-deficient renal medullary carcinoma, all of which are now recognized as molecularly defined entities in the WHO classification system (2022). While these entities each exhibit a morphologic spectrum that overlaps with other high-grade RCC, ancillary tools developed based on their distinctive molecular alterations can help establish a specific diagnosis, underscoring the importance of integrating molecular findings into diagnostic paradigms. It is important to exclude these specific tumor types in cases with similar morphologic spectrum before rendering a diagnosis of high-grade papillary RCC, collecting duct carcinoma, or RCC, NOS. Several gray areas exist within the spectrum of high-grade uncommon types of RCC, necessitating continued research to enhance diagnostic precision and therapeutic options.

Genomic alterations and diagnosis of renal cancer

The application of molecular profiling has made substantial impact on the classification of urogenital tumors. Therefore, the 2022 World Health Organization incorporated the concept of molecularly defined renal tumor entities into its classification, including succinate dehydrogenase-deficient renal cell carcinoma (RCC), FH-deficient RCC, TFE3-rearranged RCC, TFEB-altered RCC, ALK-rearranged RCC, ELOC-mutated RCC, and renal medullary RCC, which are characterized by SMARCB1-deficiency. This review aims to provide an overview of the most important molecular alterations in renal cancer, with a specific focus on the diagnostic value of characteristic genomic aberrations, their chromosomal localization, and associations with renal tumor subtypes. It may not yet be the time to completely shift to a molecular RCC classification, but undoubtedly, the application of molecular profiling will enhance the accuracy of renal cancer diagnosis, and ultimately guide personalized treatment strategies for patients.

ALK-rearranged renal cell carcinoma (ALK-RCC): Evaluation of histomorphological and immunohistochemical features by analysis of 276 renal cell carcinoma cases in Turkey

Anaplastic lymphoma kinase (ALK) rearrangement-associated renal cell carcinoma (ALK-RCC) is characterized by ALK fusion at chromosome 2p23. It has recently been included as a recognized entity with the 5th edition of the WHO classification urinary and male genital tumor. However, our knowledge about ALK-RCC is limited due to the small number of reported cases. In our study, we aimed to contribute the histomorphological and immunohistochemical features of ALK-rearranged renal cell carcinoma cases. We reviewed 276 cases diagnosed as RCC in order to detect ALKRCCs.We used immunohistochemistry to screen ALK rearrangement and then confirmed the ALK rearrangement by fluorescence in situ hybridization (FISH) method. ALK was immunohistochemically positive in 8 of 276 cases. ALK rearrangement was detected by FISH in 3 of 8 cases. These cases were previously diagnosed as clear cell renal cell carcinoma (CRCC), papillary renal cell carcinoma (PRCC), and chromophobe renal cell carcinoma (ChRCC). Their histomorphological findings were diverse, and all three cases exhibited different immunohistochemical findings. Survival of these patients ranged between 6 and 24 months. ALK immunohistochemical findings were also different in each case as perinuclear, weak cytoplasmic, and membranous.ALK RCCs appear to be very rare tumors with heterogeneous histomorphological and immunohistochemical features. Although immunohistochemistry may be useful to detect ALK positivity, genetic evaluation is required to confirm the diagnosis. With identifying ALK-RCCs, ALK inhibitors, which are currently used in the treatment of lung adenocarcinomas, can be used as a targeted therapy option in ALK-RCCs.

HOOK1 Inhibits the Progression of Renal Cell Carcinoma via TGF-β and TNFSF13B/VEGF-A Axis

Accumulating evidence shows HOOK1 disordered in human malignancies. However, the clinicopathological and biological significance of HOOK1 in renal cell carcinoma (RCC) remains rarely studied. In this study, the authors demonstrate that HOOK1 is downregulated in RCC samples with predicted poorer clinical prognosis. Mechanistically, HOOK1 inhibits tumor growth and metastasis via canonical TGF-β/ALK5/p-Smad3 and non-canonical TGF-β/MEK/ERK/c-Myc pathway. At the same time, HOOK1 inhibits RCC angiogenesis and sunitinib resistance by promoting degradation of TNFSF13B through the ubiquitin-proteasome pathway. In addition, HOOK1 is transcriptionally regulated by nuclear factor E2F3 in VHL dependent manner. Notably, an agonist of HOOK1, meletin, is screened and it shows antitumor activity more effectively when combined with sunitinib or nivolumab than it is used alone. The findings reveal a pivotal role of HOOK1 in anti-cancer treatment, and identify a novel therapeutic strategy for renal cell carcinoma.

ALK-rearranged renal cell carcinoma with TPM3::ALK gene fusion and review of the literature

ALK-rearranged renal cell carcinoma (ALK-RCC) is a very rare novel molecularly defined entity in the recently published fifth edition of the World Health Organization classification of tumours. We describe a case of ALK-RCC in a 76-year-old female. The tumour was composed of discohesive rhabdoid cells and pleomorphic, multinucleated cells (equivalent to ISUP/WHO grade 4). The tumour showed expression with PAX8, Keratin 7 and alpha methylacyl CoA racemase. ALK (D5F3 clone) was strongly and diffusely positive. ALK-FISH showed significant split signals of ALK, confirming the diagnosis. RNA sequencing showed TPM3::ALK rearrangement. Including the current case, there are 14 reported ALK-RCC cases with the same TPM3 fusion partner gene. Review of these published cases highlights their morphological heterogeneity and stresses the importance of running ALK immunohistochemistry on difficult cases to classify renal tumours. This is important while identification of ALK-RCC has clinical significance due to the availability of targeted therapy with ALK inhibitors.

Activity of ALK Inhibitors in Renal Cancer with ALK Alterations: A Systematic Review

Renal cell carcinoma (RCC) associated with anaplastic lymphoma kinase (ALK) gene rearrangements (ALK-RCC) is currently considered an “emerging or provisional” tumor entity by the last World Health Organization classification published in 2016. Although several studies assessing ALK-RCC’s clinical and histological characteristics have been published in recent years, only a few publications have evaluated the activity of ALK inhibitors (ALK-i) in this subgroup of patients. Considering the well-recognized efficacy of this evolving class of targeted therapies in other ALK-positive tumors, we conducted a systematic review to evaluate the reported activity of ALK-i in the ALK-RCC subtype. MEDLINE was searched from its inception to 7 January 2022 for case reports and case series on adult metastatic ALK-RCC patients treated with ALK-i whose therapeutic outcomes were available. A virtual cohort of ALK-RCC patients was created. Our results showed a favorable activity of first- and second-generation ALK-i in pretreated ALK-RCC patients in terms of either radiological response or performance status improvement. We hope that the present work will prompt the creation of large, multi-institutional clinical trials to confirm these promising early data.

Translocation carcinomas of the kidney

The MiT subfamily of transcription factors includes TFE3, TFEB, TFEC, and MITF. Gene fusions involving two of these transcription factors have been well-characterized in renal cell carcinoma (RCC). The TFE3-rearranged RCC (also known as Xp11 translocation RCC) was first officially recognized in the 2004 World Health Organization (WHO) renal tumor classification. The TFEB-rearranged RCC, which typically harbor a t(6;11)(p21;q12) translocation which results in a MALAT1-TFEB gene fusion, were first officially recognized in the 2016 WHO renal tumor classification. These two subtypes of translocation RCC have many similarities. Both disproportionately involve young patients, although adult translocation RCC overall outnumber pediatric cases. Both often have unusual and distinctive morphologies; the TFE3-rearranged RCCs frequently have clear cells with papillary architecture and abundant psammoma bodies, while the TFEB-rearranged RCCs frequently have a biphasic appearance with both small and large epithelioid cells and nodules of basement membrane material. However, the morphology of these two neoplasms can overlap, with one mimicking the other or other more common renal neoplasms. Both of these RCC underexpress epithelial immunohistochemical markers, such as cytokeratin and epithelial membrane antigen, relative to most other RCC. Unlike other RCC, both frequently express the cysteine protease cathepsin k and often express melanocytic markers like HMB45 and Melan A. Finally, TFE3 and TFEB have overlapping functional activity as these two transcription factors frequently heterodimerize and bind to the same targets. Therefore, these two neoplasms are now grouped together under the heading of "MiT family translocation RCC." Approximately 50 renal cell carcinomas with gene fusions involving the anaplastic lymphoma kinase (ALK) gene have now been reported. While those with a Vinculin-ALK fusion have distinctive features (predilection to affect children with sickle cell trait and to show solid architecture with striking cytoplasmic vacuolization), other ALK-fusion RCCs have more varied clinical presentations and pathologic features. This review summarizes our current knowledge of these recently described RCC.

Pediatric onco-nephrology: time to spread the word : Part I: early kidney involvement in children with malignancy

Onco-nephrology has been a growing field within the adult nephrology scope of practice. Even though pediatric nephrologists have been increasingly involved in the care of children with different forms of malignancy, there has not been an emphasis on developing special expertise in this area. The fast pace of discovery in this field, including the development of new therapy protocols with their own kidney side effects and the introduction of the CD19-targeted chimeric antigen receptor T cell (CAR-T) therapy, has introduced new challenges for general pediatric nephrologists because of the unique effects of these treatments on the kidney. Moreover, with the improved outcomes in children receiving cancer therapy come an increased number of survivors at risk for chronic kidney disease related to both their cancer diagnosis and therapy. Therefore, it is time for pediatric onco-nephrology to take its spot on the expanding subspecialties map in pediatric nephrology.

Novel, emerging and provisional renal entities: The Genitourinary Pathology Society (GUPS) update on renal neoplasia

The Genitourinary Pathology Society (GUPS) undertook a critical review of the recent advances in renal neoplasia, particularly focusing on the newly accumulated evidence post-2016 World Health Organization (WHO) classification. In the era of evolving histo-molecular classification of renal neoplasia, morphology is still key. However, entities (or groups of entities) are increasingly characterized by specific molecular features, often associated either with recognizable, specific morphologies or constellations of morphologies and corresponding immunohistochemical profiles. The correct diagnosis has clinical implications leading to better prognosis, potential clinical management with targeted therapies, may identify hereditary or syndromic associations, which may necessitate appropriate genetic testing. We hope that this undertaking will further facilitate the identification of these entities in practice. We also hope that this update will bring more clarity regarding the evolving classification of renal neoplasia and will further reduce the category of "unclassifiable renal carcinomas/tumors". We propose three categories of novel entities: (1) "Novel entity", validated by multiple independent studies; (2) "Emerging entity", good compelling data available from at least two or more independent studies, but additional validation is needed; and (3) "Provisional entity", limited data available from one or two studies, with more work required to validate them. For some entities initially described using different names, we propose new terminologies, to facilitate their recognition and to avoid further diagnostic dilemmas. Following these criteria, we propose as novel entities: eosinophilic solid and cystic renal cell carcinoma (ESC RCC), renal cell carcinoma with fibromyomatous stroma (RCC FMS) (formerly RCC with leiomyomatous or smooth muscle stroma), and anaplastic lymphoma kinase rearrangement-associated renal cell carcinoma (ALK-RCC). Emerging entities include: eosinophilic vacuolated tumor (EVT) and thyroid-like follicular renal cell carcinoma (TLFRCC). Finally, as provisional entities, we propose low-grade oncocytic tumor (LOT), atrophic kidney-like lesion (AKLL), and biphasic hyalinizing psammomatous renal cell carcinoma (BHP RCC).

ALK-rearranged Renal Cell Carcinoma (RCC): A Report of 2 Cases and Review of the Literature Emphasizing the Distinction Between VCL-ALK and Non-VCL-ALK RCC

Anaplastic lymphoma kinase (ALK) rearrangement-associated renal cell carcinoma (ALK-rearranged RCC) is a new provisional entity that has been included in the 2016 World Health Organization classification of RCCs. We report 2 cases of ALK-rearranged RCC, 1 with a vinculin-ALK (VCL-ALK) fusion and the other with an EML4-ALK fusion. The VCL-ALK RCC occurred in a 14-year-old girl with sickle cell trait and showed features similar to previously described VCL-ALK RCCs, including medullary epicenter, solid architecture, and polygonal cells with cytoplasmic vacuoles. The EML4-ALK RCC occurred in a 14-year-old boy with no evidence of sickle cell trait and had multiple less-specific growth patterns comprising tubular, solid, and tubulopapillary architectures in the desmoplastic stroma, reminiscent of collecting duct carcinoma. Both tumors demonstrated cytoplasmic and membranous ALK protein expression by immunohistochemistry. Fluorescence in situ hybridization confirmed the ALK gene rearrangements in both cases. On review in the literature, we found that solid architecture and cytoplasmic vacuoles were present significantly more frequently in VCL-ALK RCC than in non-VCL-ALK RCC, supporting the distinctive nature of the former.

ALK rearranged renal cell carcinoma (ALK-RCC): a multi-institutional study of twelve cases with identification of novel partner genes CLIP1, KIF5B and KIAA1217

ALK rearranged renal cell carcinoma (ALK-RCC) has recently been included in 2016 WHO classification as a provisional entity. In this study, we describe 12 ALK-RCCs from 8 institutions, with detailed clinical, pathological, immunohistochemical (IHC), fluorescence in situ hybridization (FISH), and next generation sequencing (NGS) analyses. Patients' age ranged from 25 to 68 years (mean, 46.3 years). Seven patients were females and five were males (M:F = 1:1.4). Tumor size ranged from 17 to 70 mm (mean 31.5, median 25 mm). The pTNM stage included: pT1a (n = 7), pT1b (n = 1), and pT3a (n = 4). Follow-up was available for 9/12 patients (range: 2 to 153 months; mean 37.6 months); 8 patients were alive without disease and one was alive with distant metastases. The tumors demonstrated heterogeneous, 'difficult to classify' morphology in 10/12 cases, typically showing diverse architectural and cellular morphologies, including papillary, tubular, tubulocystic, solid, sarcomatoid (spindle cell), rhabdoid, signet-ring cell, and intracytoplasmic vacuoles, often set in a mucinous background. Of the remaining two tumors, one showed morphology resembling mucinous tubular and spindle cell renal cell carcinoma (MTSC RCC-like) and one was indistinguishable from metanephric adenoma. One additional case also showed a focal metanephric adenoma-like area, in an otherwise heterogeneous tumor. By IHC, all tumors were diffusely positive for ALK and PAX8. In both cases with metanephric adenoma-like features, WT1 and ALK were coexpressed. ALK rearrangement was identified in 9/11 tumors by FISH. ALK fusion partners were identified by NGS in all 12 cases, including the previously reported: STRN (n = 3), TPM3 (n = 3), EML4 (n = 2), and PLEKHA7 (n = 1), and also three novel fusion partners: CLIP1 (n = 1), KIF5B (n = 1), and KIAA1217 (n = 1). ALK-RCC represents a genetically distinct entity showing a heterogeneous histomorphology, expanded herein to include unreported metanephric adenoma-like and MTSC RCC-like variants. We advocate a routine ALK IHC screening for "unclassifiable RCCs" with heterogeneous features.

ALK rearrangement in TFE3-positive renal cell carcinoma: Alternative diagnostic option to exclude Xp11.2 translocation carcinoma

Anaplastic lymphoma kinase (ALK)-rearranged renal cell carcinoma (RCC) is a rare subtype of RCC with gene fusion involving ALK at 2p23. It was first included in the renal tumor classification system by WorldHealth organization (WHO) as a distinct emerging/provisional renal entity in 2016. To date, only a few cases of ALK-RCC have been reported. Here, we report an exceptional case of ALK-RCC in a 15-year-old girl and review the literature. The patient presented with gross hematuria and a tumor measured 7 cm × 6 cm was found in the left kidney by imaging examination. Then a laparoscopic radical nephrectomy combined with local lymph node dissection was performed. The pathologic stage of the tumor was pT1bN1Mx and postoperative pathology showed that the tumor corresponded to WHO/ISUP grade 3-4. Immunohistochemistry (IHC) demonstrated moderate nuclear expression of TFE3 protein. Interestingly, ALK gene rearrangement rather than TFE3 gene rearrangement was observed by fluorescence in situ hybridization (FISH). Now the girl is still alive without evidence of recurrence for 10 months follow-up. In conclusion, the positive expression of nuclear TFE3 in immunohistochemistry may be deceptive, the detection of ALK could be a diagnostic option if TFE3 was negative in FISH study. Large-scale and long-term studies are still needed to explore the biological behavior and molecular characteristic of ALK-RCC.

Report From the International Society of Urological Pathology (ISUP) Consultation Conference on Molecular Pathology of Urogenital Cancers: III: Molecular Pathology of Kidney Cancer

Renal cell carcinoma (RCC) subtypes are increasingly being discerned via their molecular underpinnings. Frequently this can be correlated to histologic and immunohistochemical surrogates, such that only simple targeted molecular assays, or none at all, are needed for diagnostic confirmation. In clear cell RCC, VHL mutation and 3p loss are well known; however, other genes with emerging important roles include SETD2, BAP1, and PBRM1, among others. Papillary RCC type 2 is now known to include likely several different molecular entities, such as fumarate hydratase (FH) deficient RCC. In MIT family translocation RCC, an increasing number of gene fusions are now described. Some TFE3 fusion partners, such as NONO, GRIPAP1, RBMX, and RBM10 may show a deceptive fluorescence in situ hybridization result due to the proximity of the genes on the same chromosome. FH and succinate dehydrogenase deficient RCC have implications for patient counseling due to heritable syndromes and the aggressiveness of FH-deficient RCC. Immunohistochemistry is increasingly available and helpful for recognizing both. Emerging tumor types with strong evidence for distinct diagnostic entities include eosinophilic solid and cystic RCC and TFEB/VEGFA/6p21 amplified RCC. Other emerging entities that are less clearly understood include TCEB1 mutated RCC, RCC with ALK rearrangement, renal neoplasms with mutations of TSC2 or MTOR, and RCC with fibromuscular stroma. In metastatic RCC, the role of molecular studies is not entirely defined at present, although there may be an increasing role for genomic analysis related to specific therapy pathways, such as for tyrosine kinase or MTOR inhibitors.

ALK-rearranged renal cell carcinoma with a novel PLEKHA7-ALK translocation and metanephric adenoma-like morphology

ALK-rearranged renal cell carcinoma is a provisional entity in the 2016 WHO Classification of Tumors of the Urinary System and Male Genital Organs. The reported fusion partners included VCL, TPM3, EML4, STRN, and HOOK1. Herein, we present a peculiar renal cell carcinoma morphologically resembling metanephric adenoma and harboring a novel PLEKHA7-ALK fusion. Microscopically, the tumor is composed of bland epithelial cells with scant to moderate amount of amphophilic cytoplasm, round and uniform nuclei, delicate chromatin, and inconspicuous nucleoli, arranged in tightly packed small acini and angulated tubules. Papillary formation, intraluminal glomeruloid tufts, microcysts, and solid nests were focally observed. Psammomatous calcifications were evident. The tumor cells were diffusely reactive for CK7, AMACR, PAX8, and ALK, while non-reactive for WT1, BRAF V600E, CD57, carbonic anhydrase IX, TFE3, and cathepsin K. Fluorescence in situ hybridization showed breaking apart of ALK. A novel PLEKHA7exon18-ALKexon20 fusion was detected using ArcherDX FusionPlex next-generation sequencing panel and was further confirmed with reverse-transcriptase PCR. Our case demonstrates that in contrast to prior cases showing high-grade tumor cells, ALK-rearranged renal cell carcinoma may also present as a low-grade renal tumor mimicking metanephric adenoma. Immunohistochemistry and molecular testing are helpful to identify this tumor, which may be eligible for ALK inhibitor-targeted therapy.

ESC, ALK, HOT and LOT: Three Letter Acronyms of Emerging Renal Entities Knocking on the Door of the WHO Classification

Kidney neoplasms are among the most heterogeneous and diverse tumors. Continuous advancement of this field is reflected in the emergence of new tumour entities and an increased recognition of the expanding morphologic, immunohistochemical, molecular, epidemiologic and clinical spectrum of renal tumors. Most recent advances after the 2016 World Health Organization (WHO) classification of renal cell tumors have provided new evidence on some emerging entities, such as anaplastic lymphoma kinase rearrangement-associated RCC (ALK-RCC), which has already been included in the WHO 2016 classification as a provisional entity. Additionally, several previously unrecognized entities, not currently included in the WHO classification, have also been introduced, such as eosinophilic solid and cystic renal cell carcinoma (ESC RCC), low-grade oncocytic renal tumor (LOT) and high-grade oncocytic renal tumor (HOT) of kidney. Although pathologists play a crucial role in the recognition and classification of these new tumor entities and are at the forefront of the efforts to characterize them, the awareness and the acceptance of these entities among clinicians will ultimately translate into more nuanced management and improved prognostication for individual patients. In this review, we summarise the current knowledge and the novel data on these emerging renal entities, with an aim to promote their increased diagnostic recognition and better characterization, and to facilitate further studies that will hopefully lead to their formal recognition and consideration in the future classifications of kidney tumors.

Molecular Genetics of Renal Cell Tumors: A Practical Diagnostic Approach

Renal epithelial cell tumors are composed of a heterogeneous group of tumors with variable morphologic, immunohistochemical, and molecular features. A "histo-molecular" approach is now an integral part of defining renal tumors, aiming to be clinically and therapeutically pertinent. Most renal epithelial tumors including the new and emerging entities have distinct molecular and genetic features which can be detected using various methods. Most renal epithelial tumors can be diagnosed easily based on pure histologic findings with or without immunohistochemical examination. Furthermore, molecular-genetic testing can be utilized to assist in arriving at an accurate diagnosis. In this review, we presented the most current knowledge concerning molecular-genetic aspects of renal epithelial neoplasms, which potentially can be used in daily diagnostic practice.

ALK-TPM3 rearrangement in adult renal cell carcinoma: a case report and literature review

BACKGROUND

Translocation-associated renal cell carcinoma involving ALK (ALK-tRCC) is a rare subtype of adult renal cell carcinoma (RCC) reported in recent years. It was recognized as a group of emerging /provisional RCC in the latest World Health Organization's classification (2016).

CASE PRESENTATION

A new Chinese case of ALK-tRCC was reported. The patient was a 58-year-old man with a tumor in kidney. The tumor was composed of sheets of large cells with abundant eosinophilic cytoplasm and indistinct cell borders but conspicuous intracytoplasmic vacuoles. The nuclei were enlarged with a nucleolar of grade 4. Immunohistochemically, tumor cells were diffusely positive for PAX8, keratin (AE1/AE3), epithelial membrane antigen (EMA) and CK7. Fluorescent in situ hybridization (FISH) showed a rearrangement of ALK in tumor cells.

CONCLUSION

ALK-tRCC is a rare subtype of adult RCC. Its diagnosis is very difficult because the histological spectrum is very wide. We suggested that RCCs should be screened for ALK expression by immunohistochemistry (IHC) for the patient might benefit from ALK inhibitors therapy.

Distinctive mechanisms underlie the loss of SMARCB1 protein expression in renal medullary carcinoma: morphologic and molecular analysis of 20 cases

Renal medullary carcinoma is a rare but highly aggressive type of renal cancer occurring in patients with sickle cell trait or rarely with other hemoglobinopathies. Loss of SMARCB1 protein expression, a core subunit of the switch/sucrose nonfermentable (SWI/SNF) chromatin remodeling complex, has emerged as a key diagnostic feature of these tumors. However, the molecular mechanism underlying this loss remains unclear. We retrospectively identified 20 patients diagnosed with renal medullary carcinoma at two institutions from 1996 to 2017. All patients were confirmed to have sickle cell trait, and all tumors exhibited a loss of SMARCB1 protein expression by immunohistochemistry. The status of SMARCB1 locus was examined by fluorescence in situ hybridization (FISH) using 3-color probes, and somatic alterations were detected by targeted next-generation sequencing platforms. FISH analysis of all 20 cases revealed 11 (55%) with concurrent hemizygous loss and translocation of SMARCB1, 6 (30%) with homozygous loss of SMARCB1, and 3 (15%) without structural or copy number alterations of SMARCB1 despite protein loss. Targeted sequencing revealed a pathogenic somatic mutation of SMARCB1 in one of these 3 cases that were negative by FISH. Tumors in the 3 subsets with different FISH findings largely exhibited similar clinicopathologic features, however, homozygous SMARCB1 deletion was found to show a significant association with the solid growth pattern, whereas tumors dominated by reticular/cribriform growth were enriched for SMARCB1 translocation. Taken together, we demonstrate that different molecular mechanisms underlie the loss of SMARCB1 expression in renal medullary carcinoma. Biallelic inactivation of SMARCB1 occurs in a large majority of cases either via concurrent hemizygous loss and translocation disrupting SMARCB1 or by homozygous loss.

ALK-positive histiocytosis: an expanded clinicopathologic spectrum and frequent presence of KIF5B-ALK fusion

In 2008, we presented three cases of ALK-positive histiocytosis as a novel systemic histiocytic proliferation of early infancy with hepatosplenomegaly and dramatic hematological disturbances. This series of 10 cases (including the original three cases) describes an expanded clinicopathological spectrum and the molecular findings of this histiocytic proliferation. Six patients had disseminated disease: five presented in early infancy with eventual disease resolution, and the sixth presented at 2 years of age and died of intestinal, bone marrow, and brain involvement. The other four patients had localized disease involving nasal skin, foot, breast, and intracranial cavernous sinus - the first three had no recurrence after surgical resection, while the cavernous sinus lesion showed complete resolution with crizotinib therapy. The lesional histiocytes were very large, with irregularly folded nuclei, fine chromatin, and abundant eosinophilic cytoplasm, sometimes with emperipolesis. There could be an increase in foamy histiocytes and Touton giant cells with time, resembling juvenile xanthogranuloma. Immunostaining showed that the histiocytes were positive for ALK, histiocytic markers (CD68, CD163) and variably S100, while being negative for CD1a, CD207, and BRAF-V600E. Next-generation sequencing-based anchored multiplex PCR (Archer® FusionPlex®) performed in six cases identified KIF5B-ALK gene fusion in five and COL1A2-ALK fusion in one. There was no correlation of gene fusion type with disease localization or dissemination. The clinicopathological spectrum of ALK-positive histiocytosis is broader than originally described, and this entity is characterized by frequent presence of KIF5B-ALK gene fusion. We recommend that every unusual histiocytic proliferative disorder, especially disseminated lesions, be tested for ALK expression because of the potential efficacy of ALK inhibitor therapy in unresectable or disseminated disease.

Anaplastic Lymphoma Kinase (ALK) Receptor Tyrosine Kinase: A Catalytic Receptor with Many Faces

The anaplastic lymphoma kinase (ALK) receptor is a membrane-bound tyrosine kinase. The pathogenesis of several cancers is closely related to aberrant forms of ALK or aberrant ALK expression, including ALK fusion proteins, ALK-activated point mutations, and ALK amplification. Clinical applications of different ALK inhibitors represent significant progress in targeted therapy. Knowledge of different aspects of ALK biology can provide significant information to further the understanding of this receptor tyrosine kinase. In this mini-review, we briefly summarize different features of ALK. We also summarize some recent research advances on ALK fusion proteins in cancers.

The classification of pediatric and young adult renal cell carcinomas registered on the children's oncology group (COG) protocol AREN03B2 after focused genetic testing

BACKGROUND

Renal cell carcinomas (RCCs) are rare in young patients. Knowledge of their pathologic and molecular spectrum remains limited, and no prospective studies have been performed to date in this population. This study analyzes patients diagnosed with RCC who were prospectively enrolled in the AREN03B2 Children's Oncology Group (COG). The objective was to classify these tumors with the aid of focused genetic testing and to characterize their features.

METHODS

All tumors registered as RCC by central review were retrospectively re-reviewed and underwent additional ancillary studies. Tumors were classified according to the 2016 World Health Organization classification system when possible.

RESULTS

In total, 212 tumors were identified, and these were classified as microphthalmia transcription factor (MiT) translocation RCC (MiT-RCC) (41.5%), papillary RCC (16.5%), renal medullary carcinoma (12.3%), chromophobe RCC (6.6%), clear cell RCC (3.3%), fumarate hydratase-deficient RCC (1.4%), and succinate dehydrogenase-deficient RCC (0.5%). Other subtypes included tuberous sclerosis-associated RCC (4.2%), anaplastic lymphoma kinase (ALK)-rearranged RCC (3.8%), thyroid-like RCC (1.4%), myoepithelial carcinoma (0.9%), and unclassified (7.5%). MiT-RCCs were classified as either transcription factor E3 (TFE3) (93.2%) or EB (TFEB) (6.8%) translocations, and characterization of fusion partners was possible in most tumors.

CONCLUSIONS

The current study delineates the frequency of distinct RCC subtypes in a large prospective series of young patients and contributes knowledge to the diagnostic, clinical, and genetic features of MiT-RCC, the most common subtype among this age group. The identification of rare subtypes expands the spectrum of RCC in young patients, supporting the need for a thorough diagnostic workup. These studies may aid in the introduction of specific therapies for different RCC subtypes in the future. Cancer 2018. © 2018 American Cancer Society.

ALK-TPM3 rearrangement in adult renal cell carcinoma: Report of a new case showing loss of chromosome 3 and literature review

Seven cases of translocation-associated renal cell carcinoma involving ALK (ALK-tRCC) were referenced in the last World Health Organization's classification (2016), in a group of emerging/provisional RCC. The first three cases were pediatric, medullary-based, associated with sickle-cell trait and showed a fusion of ALK with VCL. Thirteen cases have been further described. They displayed clinical, morphological and genomic heterogeneity. Most of them occurred in adults. None of the patients was affected by sickle-cell disease. We report a new case of ALK-tRCC in a 55-year-old woman. Genomic profile showed losses of chromosomes 3, 9 and 14, anomalies often observed in clear cell RCC. VHL mutation or morphological features suggesting a clear cell RCC were not detected. We identified an unbalanced rearrangement of ALK and TPM3. Review of the literature identified similar features in our case and previously published cases: heterogeneous solid architecture, eosinophilic cells, mucinous cytoplasmic elements, rhabdoid cells and intracytoplasmic lumina. These elements may constitute the basis of a pathological definition of ALK-tRCC. Their observation in a RCC should lead to perform molecular detection of ALK rearrangement. This may have a crucial importance for metastatic patients treatment since ALK rearrangements confer sensitivity to tyrosine kinases inhibitors such as crizotinib.

Renal Cell Tumors: Understanding Their Molecular Pathological Epidemiology and the 2016 WHO Classification

Accumulating evidence suggests that renal cell tumors represent a group of histologically and molecularly heterogeneous diseases, even within the same histological subtype. In accordance with the increased understanding of the morphological, immunohistochemical, molecular, and epidemiological characteristics of renal cell tumors, the World Health Organization (WHO) classification of renal cell tumors has been modified. This review provides perspectives on both new and current subtypes of renal cell tumors, as well as on the emerging/provisional renal cell carcinomas in the new 2016 WHO classification, which focuses on features of their molecular pathological epidemiology. The WHO classification will require additional revisions to enable the classification of renal cell tumors as clinically meaningful subtypes and provide a better understanding of the unique characteristics of renal cell tumors.

ALK gene alterations in cancer: biological aspects and therapeutic implications

ALK was first reported in 1994 as a translocation in anaplastic large cell lymphoma and then described with different abnormalities in a number of tumors. Recently, a shortly accumulated biomedical research clarified the numerous biological processes underlying its ability to support cancer development, growth and progression. Advent of precision medicine has finally provided unexpected advances, leading to the development of ALK-targeting inhibitors with superior efficacy as compared with standard chemotherapy regimens, as well as the identification of resistance mechanisms and the creation of ‘next-generation’ treatments. This review summarizes the current understanding of ALK-driven cancers from the oncogenesis and mutation frequency by The Cancer Genome Atlas database through the diagnostic approach, to an updated portrait of available tyrosine kinase inhibitors, considering their effectiveness in cancer treatment, the molecular reasons of therapeutic failure, and the actual and future ways to overcome resistances.