Tubulocystic carcinoma of the kidney: clinicopathologic and molecular characterization. Am J Surg Pathol. 2008;32:177-187. [PMID: 18223319 DOI: 10.1097/pas.0b013e318150df1d]

Cystic Features in Renal Epithelial Neoplasms and Their Increasing Clinical and Pathologic Significance

Most cystic renal tumors after resection (Boniak IIF to IV cysts) have an indolent course despite the significantly higher proportion of malignant [ie, renal cell carcinoma (RCC)] diagnosis. Most cystic renal tumors have clear cell histology that include cystic clear cell RCC and multilocular cystic renal neoplasm of low malignant potential (MCNLMP). There is growing evidence to suggest that MCNLMP, cystic clear cell RCC, and noncystic clear cell RCC form a cystic-to-solid biological spectrum with MCNLMP representing the most indolent form and with cystic clear cell RCC behaving better than noncystic (solid) clear cell RCC. Extensively (>75%) cystic clear cell RCC also has an excellent outcome similar to MCNLMP stressing the need to reevaluate the histologic criteria that separate these 2 cystic clear cell tumors. Other tumors with clear cells that can be extensively cystic such as the recently reclassified noncancerous clear cell papillary renal tumor and the newly described MED15::TFE3 RCC also have indolent course and may mimic MCNLMP. Cystic features occur also in renal tumors with nonclear cell histology including tumors capable of metastasis such as acquired cystic disease-associated, tubulocystic, fumarate hydratase-deficient, and eosinophilic solid and cystic RCCs. Cystic imaging presentation of some renal tumors such as papillary RCC can be attributed in part to pseudocystic necrosis and hemorrhage. It is important to know that tubulocystic RCC may have a lower Bosniak class presentation that overlaps with benign renal cysts (Bosniak I to IIF) that are managed conservatively. This review highlights the cystic renal tumors with clear cell and nonclear cell morphologies including some novel RCC subtypes that may have cystic features. The presence of cystic features and their extent may aid in the classification and prognostication of renal neoplasms underscoring its increasing importance in the pathologic diagnosis and reporting of renal neoplasia.

Durable Response to Pazopanib in a Patient with Fumarate Hydratase-Mutant Tubulocystic Renal Cell Carcinoma

Tubulocystic carcinoma of the kidney (TC-RCC) is a rare renal tumor and has been recently included as a distinct entity in WHO classification of renal neoplasms. We report the case of a patient with metastatic tubulocystic RCC whose disease progressed through standard of care treatment for nonclear RCC. However, genetic analysis revealed a germline pathogenic variant of fumarate hydratase (FH) gene, and the patient had a sustained and durable response to pazopanib.

Updates in Grading of Renal Cell Carcinomas Beyond Clear Cell Renal Cell Carcinoma and Papillary Renal Cell Carcinoma

The World Health Organization (WHO) recommends grading of clear cell renal cell carcinoma (RCC) and papillary RCC using the WHO/International Society of Urological Pathology (ISUP) grade, which is primarily based on nuclear features. As the spectrum of RCC continues to evolve, with more recently described subtypes in the past decade, literature evidence on grading these subtypes is limited or not available for some tumor types. Herein, we outline a pragmatic approach to the topic of grading RCC, dividing the contemporarily described RCC subtypes into 7 categories based on the potential clinical applicability of grading as a useful prognostic parameter: (1) RCC subtypes that are reasonably validated and recommended for WHO/ISUP grading; (2) RCC subtypes where WHO/ISUP is not applicable; (3) RCC subtypes where WHO/ISUP grading is potentially clinically useful; (4) inherently aggressive RCC subtypes where histologic classification itself confers an aggressive biologic potential; (5) renal epithelial tumors where WHO/ISUP grading provides potentially misleading prognostic implication; (6) renal epithelial neoplasms where low WHO/ISUP grade features are a prerequisite for accurate histologic classification; and (7) renal epithelial neoplasms with no or limited data on grading or incomplete understanding of the biologic potential. Our aim in outlining this approach is 2-fold: (a) identify the gaps in understanding and application of grading in RCC subtypes so that researchers in the field may perform additional studies on the basis of which the important pathologic function of assignment of grade may be recommended to be performed as a meaningful exercise across a wider spectrum of RCC; and (b) to provide guidance in the interim to surgical pathologists in terms of providing clinically useful grading information in RCC based on currently available clinicopathologic information.

Tubulocystic Renal Cell Carcinoma Is Not an Indolent Tumor: A Case Report of Recurrences in the Retroperitoneum and Contralateral Kidney

Tubulocystic renal cell carcinoma (RCC) is a rare subtype of RCC that was recently included in the 2016 World Health Organization classification of tumors of the kidney. Most of these tumors exhibit indolent behavior with low metastatic potential. However, here we report a case of recurrent tubulocystic RCC with aggressive features in the retroperitoneum and contralateral kidney treated with targeted agents and radiofrequency ablation.

New developments in existing WHO entities and evolving molecular concepts: The Genitourinary Pathology Society (GUPS) update on renal neoplasia

The Genitourinary Pathology Society (GUPS) reviewed recent advances in renal neoplasia, particularly post-2016 World Health Organization (WHO) classification, to provide an update on existing entities, including diagnostic criteria, molecular correlates, and updated nomenclature. Key prognostic features for clear cell renal cell carcinoma (RCC) remain WHO/ISUP grade, AJCC/pTNM stage, coagulative necrosis, and rhabdoid and sarcomatoid differentiation. Accrual of subclonal genetic alterations in clear cell RCC including SETD2, PBRM1, BAP1, loss of chromosome 14q and 9p are associated with variable prognosis, patterns of metastasis, and vulnerability to therapies. Recent National Comprehensive Cancer Network (NCCN) guidelines increasingly adopt immunotherapeutic agents in advanced RCC, including RCC with rhabdoid and sarcomatoid changes. Papillary RCC subtyping is no longer recommended, as WHO/ISUP grade and tumor architecture better predict outcome. New papillary RCC variants/patterns include biphasic, solid, Warthin-like, and papillary renal neoplasm with reverse polarity. For tumors with 'borderline' features between oncocytoma and chromophobe RCC, a term "oncocytic renal neoplasm of low malignant potential, not further classified" is proposed. Clear cell papillary RCC may warrant reclassification as a tumor of low malignant potential. Tubulocystic RCC should only be diagnosed when morphologically pure. MiTF family translocation RCCs exhibit varied morphologic patterns and fusion partners. TFEB-amplified RCC occurs in older patients and is associated with more aggressive behavior. Acquired cystic disease (ACD) RCC-like cysts are likely precursors of ACD-RCC. The diagnosis of renal medullary carcinoma requires a negative SMARCB1 (INI-1) expression and sickle cell trait/disease. Mucinous tubular and spindle cell carcinoma (MTSCC) can be distinguished from papillary RCC with overlapping morphology by losses of chromosomes 1, 4, 6, 8, 9, 13, 14, 15, and 22. MTSCC with adverse histologic features shows frequent CDKN2A/2B (9p) deletions. BRAF mutations unify the metanephric family of tumors. The term "fumarate hydratase deficient RCC" ("FH-deficient RCC") is preferred over "hereditary leiomyomatosis and RCC syndrome-associated RCC". A low threshold for FH, 2SC, and SDHB immunohistochemistry is recommended in difficult to classify RCCs, particularly those with eosinophilic morphology, occurring in younger patients. Current evidence does not support existence of a unique tumor subtype occurring after chemotherapy/radiation in early childhood.

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.

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.

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.

A simple cyst is not always simply a cyst: A case of cystic recurrence after nephrectomy for tubulocystic renal cell carcinoma and literature review

Tubulocystic renal cell carcinoma is a rare subtype of renal tumor according to the 2016 World Health Organization, and less than 100 cases have been documented up to date in literature. The imaging features are not well known and to the best of our knowledge, there is not a radiology description of recurrence from tubulocystic renal cell carcinoma in the literature. We describe the case of a 70-year-old man with unusual cystic lesions in the left hypochondrium 11 years after a nephrectomy for tubulocystic renal cell carcinoma on the same side, and we report a review of the clinical characteristics of metastatic tubulocystic renal cell carcinoma.

Unusual Suspect: A Case Report of Tubulocystic Renal Cell Carcinoma with Features of Cystic Renal Oncocytoma

Tubulocystic renal cell carcinoma is an uncommon subtype of renal cell carcinoma that was only recently acknowledged by the World Health Organization. There is a relatively small collection of literature dedicated to the features and clinical course of this lesion. Despite its rarity, this diagnosis should remain in the differential for all cystic renal masses. We present a case report of tubulocystic renal cell carcinoma (TC-RCC) with remarkable similarity to cystic renal oncocytoma, highlighting the diagnostic challenges associated with this unusual renal malignancy.

Tubulocystic renal cell carcinoma: a distinct clinicopathologic entity with a characteristic genomic profile

Tubulocystic renal cell carcinoma, a unique tumor, was recently included as a new entity in the World Health Organization classification of renal tumors. It has variably been reported to be related to other renal cell carcinomas, including papillary renal cell carcinoma, fumarate hydratase-deficient carcinoma, and others, likely because many such carcinomas may show variable amounts of tubulocystic architecture. The published data characterizing the molecular features of these tumors are inconsistent. We studied nine "pure" tubulocystic renal cell carcinomas, as defined by International Society of Urologic Pathologists (ISUP) and World Health Organization (WHO), by targeted next-generation sequencing, and fluorescence in situ hybridization for X and Y chromosomes, to investigate if these show any unique characteristics or any overlap with known mutational/molecular profiles or copy number alterations in other subtypes of renal cell carcinoma. All nine tubulocystic carcinomas demonstrated combined losses at chromosome 9 and gains at chromosome 17, as well as, loss of chromosome Y (in 5/5). None of the tumors showed mutational profiles characteristic of other renal neoplasms, including those seen in fumarate hydratase-deficient renal cell carcinoma. Recurrent mutations in chromatin-modifying genes, KMT2C and KDM5C, were detected in two of nine tumors. Thus, tubulocystic renal cell carcinoma, if defined strictly, at the clinical and pathologic level, demonstrates genomic features distinct from other subtypes of renal cell carcinoma. These findings support the contention that tubulocystic renal cell carcinoma should be diagnosed only using strict morphological criteria and only when presenting in a "pure" form; presence of variable papillary, poorly differentiated, or other architectural patterns most likely do not belong to the category of tubulocystic renal cell carcinoma.

New entities, new technologies, new findings: A review of the cytologic features of recently established subtypes of renal cell carcinoma

Several new renal tumor types with distinctive pathologic, epidemiologic, and genetic signatures have recently been adopted in the fourth edition of the World Health Organization classification. In succeeding years, the cytologic features of most of these new types have been described, adding to the trend of increasing diagnostic accuracy for most common renal cell carcinoma subtypes and the important diagnostic role of cytologic sampling in the management and personalization of therapy. The current article reviews the cytologic findings from these recently established renal cell carcinoma subtypes. Emphasis is placed on cytologic diagnostic clues, confirmatory ancillary testing, salient differential diagnoses, and challenges that can be encountered in an attempt to render accurate interpretations in small samples.

Classification and Diagnosis of Cystic Renal Tumors: Role of MR Imaging Versus Contrast-Enhanced Ultrasound

Superior soft tissue and contrast resolution of MR imaging benefits sensitivity to kidney cyst features and classification, which may have an impact on patient management and outcomes. Contrast-enhanced ultrasound (CEUS) may have nearly similar sensitivity for detection of cyst features yet is dependent on patient body habitus and adequacy of visualization windows for the kidneys, which does not have the same impact on MR imaging results. Both MR imaging and CEUS may provide superior kidney cyst assessment compared with contrast-enhanced CT; however, further research is needed, particularly for the identification of role of CEUS.

Update on the biology and management of renal cell carcinoma

Renal cell cancer (RCC) (epithelial carcinoma of the kidney) represents 2%-4% of newly diagnosed adult tumors. Over the past 2 decades, RCC has been better characterized clinically and molecularly. It is a heterogeneous disease, with multiple subtypes, each with characteristic histology, genetics, molecular profiles, and biologic behavior. Tremendous heterogeneity has been identified with many distinct subtypes characterized. There are clinical questions to be addressed at every stage of this disease, and new targets being identified for therapeutic development. The unique characteristics of the clinical presentations of RCC have led to both questions and opportunities for improvement in management. Advances in targeted drug development and understanding of immunologic control of RCC are leading to a number of new clinical trials and regimens for advanced disease, with the goal of achieving long-term disease-free survival, as has been achieved in a proportion of such patients historically. RCC management is a promising area of ongoing clinical investigation.

Contemporary update on imaging of cystic renal masses with histopathological correlation and emphasis on patient management

This article presents an updated review of cystic renal mass imaging. Most cystic renal masses encountered incidentally are benign and can be diagnosed confidently on imaging and require no follow-up. Hyperattenuating masses discovered at unenhanced or single-phase enhanced computed tomography (CT) measuring between 20-70 HU are indeterminate and can be further investigated first by using ultrasound and, then with multi-phase CT or magnetic resonance imaging (MRI); as the majority represent haemorrhagic/proteinaceous cysts (HPCs). Dual-energy CT may improve differentiation between HPCs and masses by suppressing unwanted pseudo-enhancement observed with conventional CT. HPCs can be diagnosed confidently when measuring >70 HU at unenhanced CT or showing markedly increased signal on T1-weighted imaging. Although the Bosniak criteria remains the reference standard for diagnosis and classification of cystic renal masses, histopathological classification and current management has evolved: multilocular cystic renal cell carcinoma (RCC) has been reclassified as a cystic renal neoplasm of low malignant potential, few Bosniak 2F cystic masses progress radiologically during follow-up; RCC with predominantly cystic components are less aggressive than solid RCC; and Bosniak III cystic masses behave non-aggressively. These advances have led to an increase in non-radical management or surveillance of cystic renal masses including Bosniak 3 lesions. Tubulocystic RCC is a newly described entity with distinct imaging characteristics, resembling a pancreatic serous microcystadenoma. Other benign cystic masses including: mixed epithelial stromal tumours (MEST) are now considered in the spectrum of cystic nephroma and angiomyolipoma (AML) with epithelial cysts (AMLEC) resemble a fat-poor AML with cystic components.

Tubulocystic renal cell carcinoma: a review of literature focused on radiological findings for differential diagnosis

Tubulocystic renal cell carcinoma (TC-RCC) has been classified as an independent subtype according to the 2016 World Health Organization (WHO) classification. It is a rare subtype that predominantly affects men. Although few in number, radiological imaging reports have suggested that TC-RCC is characterized by multilocular cystic lesions, which are categorized as the Bosniak classification II-IV, with signature pathological characteristics comprising numerous small cysts or a tubular structure. The Bosniak classification system facilitates patient management; however, the differentiation of cystic tumors exhibiting similar imaging findings remains impossible; in fact, the differentiation of multilocular cystic RCC, adult cystic nephroma, and mixed epithelial and stromal tumor remains challenging. This review aims to discuss TC-RCC with a focus on implications of radiological findings in the differential diagnosis of TC-RCC.

Tubulocystic Carcinoma of the Bile Duct

Tubulocystic carcinoma of the bile duct is extremely rare and has not been reported in the literature. We reported a case of cystic neoplasm of the liver with distinct histopathological features that could not be clearly classified as of either mucinous or intraductal papillary neoplasm. A 68-year-old Japanese patient had a multicystic biliary tumor within the liver. This tumor was detected on follow-up of polymyalgia rheumatica. The exophytic, multicystic, 35 × 50 mm mass was composed of complex tubulocystic structures. We initially suspected cystadenocarcinoma of the liver and performed radical operation. However, pathology ultimately showed it to be very rare tubulocystic carcinoma that derived from the bile duct. We reviewed the literature and describe the process of our differential diagnosis.

Noncoding RNA Expression and Targeted Next-Generation Sequencing Distinguish Tubulocystic Renal Cell Carcinoma (TC-RCC) from Other Renal Neoplasms

Tubulocystic renal cell carcinoma (TC-RCC) is a rare recently described renal neoplasm characterized by gross, microscopic, and immunohistochemical differences from other renal tumor types and was recently classified as a distinct entity. However, this distinction remains controversial particularly because some genetic studies suggest a close relationship with papillary RCC (PRCC). The molecular basis of this disease remains largely unexplored. We therefore performed noncoding (nc) RNA/miRNA expression analysis and targeted next-generation sequencing mutational profiling on 13 TC-RCC cases (11 pure, two mixed TC-RCC/PRCC) and compared with other renal neoplasms. The expression profile of miRNAs and other ncRNAs in TC-RCC was distinct and validated 10 differentially expressed miRNAs by quantitative RT-PCR, including miR-155 and miR-34a, that were significantly down-regulated compared with PRCC cases (n = 22). With the use of targeted next-generation sequencing we identified mutations in 14 different genes, most frequently (>60% of TC-RCC cases) in ABL1 and PDFGRA genes. These mutations were present in <5% of clear cell RCC, PRCC, or chromophobe RCC cases (n > 600) of The Cancer Genome Atlas database. In summary, this study is by far the largest molecular study of TC-RCC cases and the first to investigate either ncRNA expression or their genomic profile. These results add molecular evidence that TC-RCC is indeed a distinct entity from PRCC and other renal neoplasms.

Is Tubulocystic Renal Cell Carcinoma Real?: Genomic Analysis Confirms the World Health Organization Classification

This commentary highlights the article by Lawrie et al that validates that tubulocystic renal cell carcinoma is a distinct type of renal neoplasm.

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.

Molecular Genetic Alterations in Renal Cell Carcinomas With Tubulocystic Pattern: Tubulocystic Renal Cell Carcinoma, Tubulocystic Renal Cell Carcinoma With Heterogenous Component and Familial Leiomyomatosis-associated Renal Cell Carcinoma. Clinicopathologic and Molecular Genetic Analysis of 15 Cases

The characteristic morphologic spectrum of tubulocystic renal cell carcinoma (TC-RCC) may include areas resembling papillary RCC (PRCC). Our study includes 15 RCCs with tubulocystic pattern: 6 TC-RCCs, 1 RCC-high grade with tubulocystic architecture, 5 TC-RCCs with foci of PRCC, 2 with high-grade RCC (HGRCC) not otherwise specified, and 1 with a clear cell papillary RCC/renal angiomyoadenomatous tumor-like component. We analyzed aberrations of chromosomes 7, 17, and Y; mutations of VHL and FH genes; and loss of heterozygosity at chromosome 3p. Genetic analysis was performed separately in areas of classic TC-RCC and in those with other histologic patterns. The TC-RCC component demonstrated disomy of chromosome 7 in 9/15 cases, polysomy of chromosome 17 in 7/15 cases, and loss of Y in 1 case. In the PRCC component, 2/3 analyzable cases showed disomy of chromosome 7 and polysomy of chromosome 17 with normal Y. One case with focal HGRCC exhibited only disomy 7, whereas the case with clear cell papillary RCC/renal angiomyoadenomatous tumor-like pattern showed polysomies of 7 and 17, mutation of VHL, and loss of heterozygosity 3p. FH gene mutation was identified in a single case with an aggressive clinical course and predominant TC-RCC pattern. The following conclusions were drawn: (1) TC-RCC demonstrates variable status of chromosomes 7, 17, and Y even in cases with typical/uniform morphology. (2) The biological nature of PRCC/HGRCC-like areas within TC-RCC remains unclear. Our data suggest that heterogenous TC-RCCs may be associated with an adverse clinical outcome. (3) Hereditary leiomyomatosis-associated RCC can be morphologically indistinguishable from "high-grade" TC-RCC; therefore, in TC-RCC with high-grade features FH gene status should be tested.

Imaging features of papillary renal cell carcinoma with cystic change-dominant appearance in the era of the 2016 WHO classification

PURPOSE

Papillary renal cell carcinoma (P-RCC) typically exhibits a homogeneous, solid hypovascular mass; P-RCC with a cystic appearance is atypical. Tubulocystic RCC (TC-RCC), a newly proposed entity for renal tumors in the 2016 WHO classification, and cystic papillary RCC, may yield similar imaging findings. Therefore, we investigated the incidence of papillary RCC with cystic changes and compared its CT and pathologic features to differentiate between two entities.

METHODS

We retrospectively evaluated 26 consecutive patients diagnosed with P-RCC. Two radiologists consensually identified dominant masses indicative of cystic changes on CT scans and recorded their Bosniak classification. In addition, two pathologists inspected the whole area of tumors macroscopically, labeled them as solid- or cystic change-dominant tumors, determined the pathogenesis of the cystic components (necrosis or hemorrhage), and recorded their inherent cystic characteristics (with/without TC-RCC components). We defined masses with cystic changes involving more than 50% of the entire tumor as cystic change-dominant tumors.

RESULTS

Of the 26 tumors, 7 (27%) were diagnosed cystic change-dominant based on imaging and pathologic findings, of these, 2 were classified as Bosniak type III and 5 as Bosniak type IV. The pathologists confirmed that two type IV tumors demonstrated extensive necrosis and one type IV tumor revealed extensive hemorrhage. Four P-RCCs (type III and IV, 2 each) were of a mixed type harboring both solid and cystic components. Only one tumor exhibited a multilocular cystic appearance. All 7 cystic change-dominant P-RCCs were pathologically diagnosed as a pure P-RCC without TC-RCC components.

CONCLUSION

While P-RCCs may contain cystic features, the multilocular type of cystic P-RCC is rare.

Morphologic, Molecular, and Taxonomic Evolution of Renal Cell Carcinoma: A Conceptual Perspective With Emphasis on Updates to the 2016 World Health Organization Classification

Molecular and morphologic interrogation has driven a much-needed reexamination of renal cell carcinoma (RCC). Indeed, the recently released 2016 World Health Organization classification now recognizes 12 distinct RCC subtypes, as well as several other emerging/provisional RCC entities. From a clinical perspective, accurate RCC classification may have important implications for patients and their families, including prognostic risk stratification, targeted therapeutics selection, and identification for genetic testing. In this review, we provide a conceptual framework for approaching RCC diagnosis and classification by categorizing RCCs as tumors with clear cytoplasm, papillary architecture, and eosinophilic (oncocytic) cytoplasm. The currently recognized 2016 World Health Organization classification for RCC subtypes is briefly discussed, including new diagnostic entities (clear cell papillary RCC, hereditary leiomyomatosis and RCC-associated RCC, succinate dehydrogenase-deficient RCC, tubulocystic RCC, and acquired cystic disease-associated RCC) and areas of evolving RCC classification, such as transcription elongation factor B subunit 1 (TCEB1)-mutated RCC/RCC with angioleiomyoma-like stroma/RCC with leiomyomatous stroma, RCC associated with anaplastic lymphoma receptor tyrosine kinase (ALK) gene rearrangement, thyroidlike follicular RCC, and RCC in neuroblastoma survivors. For each RCC subtype, relevant clinical, molecular, gross, and microscopic findings are reviewed, and ancillary studies helpful for its differential diagnosis are presented, providing a practical approach to modern RCC classification.

Classification of Adult Renal Tumors: An Update

The fourth edition of the World Health Organization (WHO) report was published in January 2016 and focused especially on the kidney tumors and several new concepts. Many steps forward in the subclassification have been taken. Several new entities have been added, as major progress on a genetic level has been made. Some already well-known entities have new prognosis in accordance with longer follow up and research, and some concepts of well-known groups have been refined.

Tubulocystic Carcinoma of the Kidney With Poorly Differentiated Foci: A Frequent Morphologic Pattern of Fumarate Hydratase-deficient Renal Cell Carcinoma

An emerging group of high-grade renal cell carcinomas (RCCs), particularly carcinomas arising in the hereditary leiomyomatosis renal cell carcinoma syndrome (HLRCC), show fumarate hydratase (FH) gene mutation and loss of function. On the basis of similar cytomorphology and clinicopathologic features between these tumors and cases described as tubulocystic carcinomas with poorly differentiated foci (TC-PD) of infiltrative adenocarcinoma, we hypothesized a relationship between these entities. First, 29 RCCs with morphology of TC-PD were identified retrospectively and assessed for FH expression and aberrant succination (2SC) by immunohistochemistry (IHC), with targeted next-generation sequencing of 409 genes-including FH-performed on a subset. The 29 TC-PD RCCs included 21 males and 8 females, aged 16 to 86 years (median, 46), with tumors measuring 3 to 21 cm (median, 9) arising in the right (n=16) and left (n=13) kidneys. Family history or stigmata of HLRCC were identifiable only retrospectively in 3 (12%). These tumors were aggressive, with 79% showing perinephric extension, nodal involvement in 41%, and metastasis in 86%. Of these, 16 (55%) demonstrated loss of FH by IHC (14/14 with positive 2SC). In contrast, 5 (17%) showed a wild-type immunoprofile of FH+/2SC-. An intriguing group of 8 (28%) showed variable FH± positivity, but with strong/diffuse 2SC+. Next-generation sequencing revealed 8 cases with FH mutations, including 5 FH-/2SC+ and 3 FH±/2SC+ cases, but none in FH+/2SC- cases. Secondly, we retrospectively reviewed the morphology of 2 well-characterized cohorts of RCCs with FH-deficiency determined by IHC or sequencing (n=23 and n=9), unselected for TC-PD pattern, identifying the TC-PD morphology in 10 (31%). We conclude that RCCs with TC-PD morphology are enriched for FH deficiency, and we recommend additional workup, including referral to genetic counseling, for prospective cases. In addition, based on these and other observations, we propose the term "FH-deficient RCC" as a provisional term for tumors with a combination of suggestive morphology and immunophenotype but where genetic confirmation is unavailable upon diagnosis. This term will serve as a provisional nomenclature that will enable triage of individual cases for genetic counseling and testing, while designating these cases for prospective studies of their relationship to HLRCC.

Tubulocystic Renal Cell Carcinoma: A Great Imitator

Tubulocystic renal cell carcinoma (TCRC) is a rare renal tumor. Patients are usually asymptomatic; it is usually detected incidentally, during imaging studies for Bosniak type III and type IV renal cysts. These tumors rarely metastasize. The role of targeted therapy in such rare tumors is still controversial. We report a case of TCRC initially presented as a Bosniak type II renal cyst and was discovered ultimately to be a metastatic disease. This type of presentation might broaden our understanding of this rare disease.

Molecular genetics and immunohistochemistry characterization of uncommon and recently described renal cell carcinomas

Renal cell carcinoma (RCC) compromises multiple types and has been emerging dramatically over the recent several decades. Advances and consensus have been achieved targeting common RCCs, such as clear cell carcinoma, papillary RCC and chromophobe RCC. Nevertheless, little is known on the characteristics of several newly-identified RCCs, including clear cell (tubulo) papillary RCC, Xp11 translocation RCC, t(6;11) RCC, succinate dehydrogenase (SDH)-deficient RCC, acquired cystic disease-associated RCC, hereditary leiomyomatosis RCC syndrome-associated RCC, ALK translocation RCC, thyroid-like follicular RCC, tubulocystic RCC and hybrid oncocytic/chromophobe tumors (HOCT). In current review, we will collect available literature of these newly-described RCCs, analyze their clinical pathologic characteristics, discuss their morphologic and immunohistologic features, and finally summarize their molecular and genetic evidences. We expect this review would be beneficial for the understanding of RCCs, and eventually promote clinical management strategies.

[Vancouver classification of renal tumors: Recommendations of the 2012 consensus conference of the International Society of Urological Pathology (ISUP)]

The 2012 consensus conference of the International Society of Urological Pathology (ISUP) has formulated recommendations on classification, prognostic factors and staging as well as immunohistochemistry and molecular pathology of renal tumors. Agreement was reached on the recognition of five new tumor entities: tubulocystic renal cell carcinoma (RCC), acquired cystic kidney disease-associated RCC, clear cell (tubulo) papillary RCC, microphthalmia transcription factor family RCC, in particular t(6;11) RCC and hereditary leiomyomatosis-associated RCC. In addition three rare forms of carcinoma were considered as emerging or provisional entities: thyroid-like follicular RCC, succinate dehydrogenase B deficiency-associated RCC and anaplastic lymphoma kinase (ALK) translocation RCC. In the new ISUP Vancouver classification, modifications to the existing 2004 World Health Organization (WHO) specifications are also suggested. Tumor morphology, a differentiation between sarcomatoid and rhabdoid and tumor necrosis were emphasized as being significant prognostic parameters for RCC. The consensus ISUP grading system assigns clear cell and papillary RCCs to grades 1-3 due to nucleolar prominence and grade 4 is reserved for cases with extreme nuclear pleomorphism, sarcomatoid and/or rhabdoid differentiation. Furthermore, consensus guidelines were established for the preparation of samples. For example, agreement was also reached that renal sinus invasion is diagnosed when the tumor is in direct contact with the fatty tissue or loose connective tissue of the sinus (intrarenal peripelvic fat) or when endothelialized cavities within the renal sinus are invaded by the tumor, independent of the size. The importance of biomarkers for the diagnostics or prognosis of renal tumors was also emphasized and marker profiles were formulated for use in specific differential diagnostics.

The 2016 WHO Classification of Tumours of the Urinary System and Male Genital Organs-Part A: Renal, Penile, and Testicular Tumours

The fourth edition of the World Health Organization (WHO) classification of urogenital tumours (WHO "blue book"), published in 2016, contains significant revisions. These revisions were performed after consideration by a large international group of pathologists with special expertise in this area. A subgroup of these persons met at the WHO Consensus Conference in Zurich, Switzerland, in 2015 to finalize the revisions. This review summarizes the most significant differences between the newly published classification and the prior version for renal, penile, and testicular tumours. Newly recognized epithelial renal tumours are hereditary leiomyomatosis and renal cell carcinoma (RCC) syndrome-associated RCC, succinate dehydrogenase-deficient RCC, tubulocystic RCC, acquired cystic disease-associated RCC, and clear cell papillary RCC. The WHO/International Society of Urological Pathology renal tumour grading system was recommended, and the definition of renal papillary adenoma was modified. The new WHO classification of penile squamous cell carcinomas is based on the presence of human papillomavirus and defines histologic subtypes accordingly. Germ cell neoplasia in situ (GCNIS) of the testis is the WHO-recommended term for precursor lesions of invasive germ cell tumours, and testicular germ cell tumours are now separated into two fundamentally different groups: those derived from GCNIS and those unrelated to GCNIS. Spermatocytic seminoma has been designated as a spermatocytic tumour and placed within the group of non-GCNIS-related tumours in the 2016 WHO classification.

PATIENT SUMMARY

The 2016 World Health Organization (WHO) classification contains new renal tumour entities. The classification of penile squamous cell carcinomas is based on the presence of human papillomavirus. Germ cell neoplasia in situ of the testis is the WHO-recommended term for precursor lesions of invasive germ cell tumours.

A case of tubulocystic carcinoma of the kidney with aggressive features

Tubulocystic carcinoma of the kidney is rare and typically indolent. Our case involved an aggressive tubulocystic carcinoma as well as the radiological confirmation of its relation to papillary renal cell carcinoma. A 46-year-old male presented with renal multiloculated cysts with a solid part. On computed tomography and magnetic resonance imaging, the solid part showed the characteristics of papillary renal cell carcinoma. Contrast enhancement of the solid part was fluffy and sparse because of the coexistence of cysts. Perirenal fat invasion resulted in exophytic cysts, and renal-hilar cystic lymph node metastasis existed. The histopathological diagnosis was tubulocystic carcinoma associated with areas of papillary renal cell carcinoma and poorly differentiated carcinoma with metastasis. Our case suggests that the solid part enhancement of tubulocystic carcinoma tends to be fluffy and sparse, and exophytic cysts and cystic lymph nodes may show radiologically aggressive findings.

Rapidly Progressive Renal Dysfunction in Two Elderly Patients with Renal Enlargement and Medullary Cystic Kidney Disease-like Acute Tubulointerstitial Injury

Medullary cystic kidney disease (MCKD) is a hereditary disease associated with bilateral medullary polycysts and interstitial fibrosis. MCKD is typically associated with slowly progressive renal dysfunction. We herein report two rare elderly cases with enlarged kidneys and rapidly progressive renal dysfunction without myeloperoxidase anti-neutrophil cytoplasmic antibody (MPO-ANCA), PR3-ANCA, or anti-glomerular basement membrane (GBM) antibodies. Renal biopsies revealed extensive tubular dilatation and atrophy with interstitial fibrosis consistent with MCKD. Both patients began hemodialysis therapy a few months later. Our cases suggest a MCKD subgroup among elderly patients with an undefined genetic background, rapidly progressive renal dysfunction, and enlarged kidneys.

Emerging Entities in Renal Neoplasia

This article reviews emerging entities in renal epithelial neoplasia, including tubulocystic carcinoma, clear-cell-papillary renal cell carcinoma (RCC), thyroid-like follicular RCC, ALK-related RCC, translocation RCC, acquired cystic disease-related RCC, succinate dehydrogenase-deficient RCC, and hereditary leiomyomatosis-RCC syndrome-associated RCC. Many of these rarer subtypes of RCC were recently studied in more depth and are included in the upcoming version of the World Health Organization classification of tumors. Emphasis is placed on common gross and morphologic features, differential diagnoses, use of ancillary studies for making accurate diagnoses, molecular alterations, and predicted biologic behavior based on previous studies.

Intraductal tubulopapillary neoplasms of the bile ducts: clinicopathologic, immunohistochemical, and molecular analysis of 20 cases

Intraductal tubulopapillary neoplasm is a well-established entity in the pancreas. A similar, if not identical, tumor occurs also in the biliary tract. We conducted a multicenter study of 20 such lesions, focusing on their clinicopathologic characteristics and molecular profile. Biliary intraductal tubulopapillary neoplasms were seen in patients in their 60s (mean 62 years). The tumors were intrahepatic 70%, extrahepatic 10%, and perihilar 20%; mean tumor size was 6.9 cm. Histologically, all intraductal tubulopapillary neoplasms showed, in addition to their typical tubular pattern, solid areas (70%) or abortive papillae (50%). Necrosis was common (85%), predominantly focal (40%), and with 'comedocarcinoma-like pattern' in 40%. Immunohistochemically, these neoplasms were characterized by the expression of MUC1 (80%) and MUC6 (30%) and by the absence of MUC2 and MUC5AC. Associated invasive carcinomas were present in 16 (80%), mainly conventional tubular adenocarcinoma (50%). The molecular alterations observed included CDKN2A/p16 (intraductal components 44%, invasive 33%) and TP53 (intraductal components 17%, invasive 9%). Mutations in KRAS (intraductal 6%, invasive 0%), PIK3CA (intraductal 6%, invasive 0%), and loss of SMAD4/DPC4 (intraductal 7%, invasive 0%) were rare. No alterations/mutations were identified in IDH1/2, BRAF, GNAS, EGFR, HER2, and β-catenin. Follow-up information was available for 17 patients (85%) with mean follow-up 44 months. Overall combined survival rates showed favorable prognosis: 1 year 100%, 3 years 90%, and 5 years 90%. In conclusion, despite the relatively high incidence of invasive carcinoma (80%), available follow-up suggests that biliary intraductal tubulopapillary neoplasms have an indolent behavior. Molecular analyses highlight the low prevalence of alterations of common oncogenic signaling pathways in intraductal tubulopapillary neoplasm. Further studies using whole-exome sequencing are required to discover yet unknown molecular changes and to understand the carcinogenesis of intraductal tubulopapillary neoplasms.

Tubulocystic renal cell carcinoma: a new radiological entity

Tubulocystic renal cell carcinoma (TC-RCC) is a recently identified renal malignancy. While approximately 100 cases of TC-RCC have been reported in the pathology literature, imaging features have not yet been clearly described. The purpose of this review is to describe the main radiologic features of this rare sub-type of RCC on ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI), based jointly on the literature and findings from a multi-institutional retrospective HIPAA-compliant review of pathology and imaging databases. Using a combination of sonographic and CT/MRI features, diagnosis of TC-RCC appeared to be strongly suggested in many cases.

KEY POINTS

• Tubulocystic renal cell carcinoma is a new entity with typical imaging features • Diagnosis of tubulocystic renal cell carcinoma can be suggested preoperatively by imaging • Cystic renal lesions with high echogenicity may correspond to tubulocystic carcinoma.

Tubulocystic carcinoma of the kidney

Tubulocystic carcinoma (TCC) of the kidney is a unique, rare, and recently recognized neoplasm. Although originally considered a low-grade collecting duct carcinoma, TCC is now considered to be a distinct entity. TCC should be considered in the differential diagnosis of cystic renal neoplasms. We report a case of TCC arising in the left kidney.

Distal nephron neoplasms

Tumours of the distal nephron are uncommon but can create diagnostic difficulties. They may be divided into three groups-tumours of intercalated cell phenotype, those of principal cell phenotype and others with an unconfirmed distal nephron origin. Oncocytomas, chromophobe carcinoma and hybrid oncocytoma chromophobe carcinoma, all show features of intercalated cells and the distinction amongst these is one of the most common areas of diagnostic dilemma. Collecting duct carcinoma and renal medullary carcinoma are the most aggressive forms of renal cancer but recent evidence suggests they may respond to targeted therapy so their recognition becomes crucial to the management of these patients. There remains debate over the precise phenotype of both tubulocystic carcinoma and mucinous tubular and spindle cell carcinoma.

The evolving classification of renal cell neoplasia

The classification of renal cell neoplasia is morphologically based; however, this has evolved over the last 35 years with the incorporation of genetic characteristics into the diagnostic features of some tumors. The 2013 Vancouver classification recognized 17 morphotypes of renal parenchymal malignancy and two benign tumors. This classification included the newly established entities tubulocystic renal cell carcinoma (RCC)), acquired cystic disease-associated RCC, clear cell (tubulo) papillary RCC, microphthalmia transcription factor family translocation RCC and hereditary leiomyomatosis RCC syndrome-associated RCC. In addition to these newly described forms of RCC there are a number of novel tumors that are currently recognized as emerging entities. These are likely to be incorporated into subsequent classifications and include thyroid-like follicular RCC, succinate dehydrogenase B mutation-associated RCC, ALK translocation RCC, tuberous sclerosis complex-associated RCC, and RCC with (angio) leiomyomatous stroma.

Two Unexpected Tumors in a Laparoscopic Nephrectomy Specimen, Including a Rare Tubulocystic Renal-Cell Carcinoma: A Case Report

We present a case of a 52-year-old Caucasian male who underwent a laparoscopic nephrectomy for an atrophic kidney and was found to have two unexpected, synchronous kidney cancers. He had a remote history of testicular cancer complicated by lymphadenopathy and external ureteral compression. Over time, he developed an atrophic left kidney from obstructive uropathy. Years later, due to flank pain and renal scintigraphy showing minimal function, a laparoscopic nephrectomy was performed. Final pathology demonstrated papillary renal-cell carcinoma (RCC) and tubulocystic RCC. Tubulocystic RCC is a rare neoplasm thought to be an indolent subset of collecting duct carcinoma, but was identified as a unique entity in 2004. Currently, there are ∼100 cases of this neoplasm in the literature.