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

Mechanisms of tropomyosin 3 in the development of malignant tumors

Tropomyosin (TPM) is an important regulatory protein that binds to actin in fine myofilaments, playing a crucial role in the regulation of muscle contraction. TPM3, as one of four tropomyosin genes, is notably prevalent in eukaryotic cells. Traditionally, abnormal gene expression of TPM3 has been exclusively associated with myopathy. However, recent years have witnessed a surge in studies highlighting the close correlation between abnormal expression of TPM3 and the onset, progression, metastasis, and prognosis of various malignant tumors. In light of this, investigating the mechanisms underlying the pathogenetic role of TPM3 holds significant promise for early diagnosis and more effective treatment strategies. This article aims to provide an insightful review of the structural characteristics of TPM3 and its intricate role in the occurrence and development of malignant tumors.

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.

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.

From LncRNA to metastasis: The MALAT1-EMT axis in cancer progression

Cancer is a complex disease that causes abnormal genetic changes and unchecked cellular growth. It also causes a disruption in the normal regulatory processes that leads to the creation of malignant tissue. The complex interplay of genetic, environmental, and epigenetic variables influences its etiology. Long non-coding RNAs (LncRNAs) have emerged as pivotal contributors within the intricate landscape of cancer biology, orchestrating an array of multifaceted cellular processes that substantiate the processes of carcinogenesis and metastasis. Metastasis is a crucial driver of cancer mortality. Among these, MALAT1 (Metastasis-Associated Lung Adenocarcinoma Transcript 1) has drawn a lot of interest for its function in encouraging metastasis via controlling the Epithelial-Mesenchymal Transition (EMT) procedure. MALAT1 exerts a pivotal influence on the process of EMT, thereby promoting metastasis to distant organs. The mechanistic underpinning of this phenomenon involves the orchestration of an intricate regulatory network encompassing transcription factors, signalling cascades, and genes intricately associated with the EMT process by MALAT1. Its crucial function in transforming tumor cells into an aggressive phenotype is highlighted by its capacity to influence the expression of essential EMT effectors such as N-cadherin, E-cadherin, and Snail. An understanding of the MALAT1-EMT axis provides potential therapeutic approaches for cancer intervention. Targeting MALAT1 or its downstream EMT effectors may reduce the spread of metastatic disease and improve the effectiveness of already available therapies. Understanding the MALAT1-EMT axis holds significant clinical implications. Therefore, directing attention towards MALAT1 or its downstream mediators could present innovative therapeutic strategies for mitigating metastasis and improving patient prognosis. This study highlights the importance of MALAT1 in cancer biology and its potential for cutting back on metastatic disease with novel treatment strategies.

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.

RBM10-TFE3 fusions: A FISH-concealed anomaly in adult renal cell carcinomas displaying a variety of morphological and genomic features: Comprehensive study of six novel cases

The accurate diagnosis of Xp11-translocation renal cell carcinoma (RCC) in adults is challenging. TFE3 (located on chromosome X) fuses with a partner gene generally located on another chromosome. In rare cases TFE3 may fuse with a neighboring gene: RBM10. Because TFE3 false-positive immunostaining is a common pitfall in many laboratories, demonstration of the chromosomal rearrangement is required in order to ascertain the diagnosis. Fluorescence in situ hybridization (FISH)-that has been considered as the gold standard method-reaches its limits for detecting small Xp11 paracentric inversions. We performed a comprehensive clinical, histological and genomic study of six novel cases of RCC with RBM10-TFE3 fusion. Using FISH, TFE3 rearrangement was equivocal in one case and negative in others. RBM10-TFE3 fusion was discovered using targeted RNA sequencing (RNASeq). As all the previously reported cases (mean age: 50), the six patients were adults (mean age: 42), suggesting an epidemiologic difference between RBM10-TFE3 RCC and tumors harboring some other partner genes, such as ASPSCR1 that rather occur in children. Array-comparative genomic hybridization showed several alterations, notably a gain of 17q in four cases with papillary features and loss of 3p in one case with clear cells. Our study demonstrates that, though rare among adult cases of RCC, RBM10-TFE3 fusion is not exceptional and warrants appropriate molecular detection. Notably, it would be worthy to systemically investigate by RNASeq challenging RCC with type-2 papillary features and 17q gain.

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.

Towards a new WHO classification of renal cell tumor: what the clinician needs to know-a narrative review

In 1952, renal cell carcinomas had been divided into 2 categories—clear cell or granular cell—depending upon their cytoplasmic staining characteristics. In the following years, the inventory of renal epithelial tumors has expanded by the addition of tumors named by their architectural pattern (i.e., papillary RCC, tubulocystic RCC), anatomic location (i.e., collecting duct carcinoma, renal medullary carcinoma), associated diseases (i.e., acquired cystic disease-associated RCCs). With the extensive application of molecular diagnostic techniques, it becomes possible to detect genetic distinctions between various types of renal neoplasm and discover new entities, otherwise misdiagnosed or diagnosed as unclassified RCC. Some tumors such as ALK rearrangement-associated RCC, MiT family translocation renal carcinomas, SDH-deficient renal cancer or FH-deficient RCC, are defined by their molecular characteristics. The most recent World Health Organization (WHO) classification of renal neoplasms account for more than 50 entities and provisional entities. New entities might be included in the upcoming WHO classification. The aim of this review is to summarise and discuss the newly acquired data and evidence on the clinical, pathological, molecular features and on the prognosis of new RCC entities, which will hopefully increase the awareness and the acceptance of these entities among clinicians and improve prognostication for individual patients.

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.

Renal Cell Tumors: Molecular Findings Reshaping Clinico-pathological Practice

Over the past 20 years, the number of subtypes of renal epithelial cell neoplasia has grown. This growth has resulted from detailed histological and immunohistochemical characterization of these tumors and their correlation with clinical outcomes. Distinctive molecular phenotypes have validated the unique nature of many of these tumors. This growth of unique renal neoplasms has continued after the 2016 World Health Organization (WHO) Classification of Tumours. A consequence is that both the pathologists who diagnose the tumors and the clinicians who care for these patients are confronted with a bewildering array of renal cell carcinoma variants. Many of these variants have important clinical features, i.e. familial or syndromic associations, genomics alterations that can be targeted with systemic therapy, and benignancy of tumors previously classified as carcinomas. Our goal in the review is to provide a practical guide to help recognize these variants, based on small and distinct sets of histological features and limited numbers of immunohistochemical stains, supplemented, as necessary, with molecular features.

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.

Characteristics of Renal Cell Carcinoma Harboring TPM3-ALK Fusion

The World Health Organization 2016 edition assigned anaplastic lymphoma kinase (ALK) rearrangement-associated renal cell carcinoma (ALK-RCC) as an emerging renal tumor entity. Identifying ALK-RCC is important because ALK inhibitors have been shown to be effective in treatment. Here, we report the case of a 14-year-old young man with ALK-RCC. Computed tomography revealed a well-demarcated 5.3-cm enhancing mass at the upper pole of the left kidney. There was no further history or symptoms of the sickle-cell trait. The patient underwent left radical nephrectomy. Pathologically, the mass was diagnosed as an unclassified RCC. Targeted next-generation sequencing identified a TPM3-ALK fusion gene. The present report and literature review demonstrate that TPM3-ALK RCC may be associated with distinct clinicopathological features. Microscopically, the tumors showed diffuse growth and tubulocystic changes with inflammatory cell infiltration. Tumor cells were dis-cohesive and epithelioid with abundant eosinophilic cytoplasm and cytoplasmic vacuoles. If morphological features and TFE3 expression are present in adolescent and young patients, molecular tests for ALK translocation should be performed. This awareness is critically important, because ALK rearrangement confers sensitivity to ALK 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.

ALK-rearranged renal cell carcinomas in Polish population

Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase, the activation of which is considered an important event in the pathogenesis of several neoplasms and a predictive factor for the targeted therapy with ALK inhibitors. Thus far, ALK rearrangements have been identified in 22 renal cell carcinomas in both pediatric and adult patients. We evaluated the incidence of ALK rearrangement-associated RCC in adult Central European population. An immunohistochemical evaluation of 1019 kidney tumors was performed with use of three different clones of anti-ALK antibodies. None of the tested samples showed positive staining, which suggests that the incidence of ALK rearrangement-associated renal cell carcinomas is significantly lower in the Polish population, and indicates a potential association between ethnicity and occurrence of these rare neoplasms.