Succinate dehydrogenase (SDH)-deficient renal carcinoma: a morphologically distinct entity: a clinicopathologic series of 36 tumors from 27 patients

Renal cell carcinoma with succinate dehydrogenase A mutation: A case report and literature review

Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is a rare subtype of RCC characterized by the presence of a germline mutation in one of the four subunits of the SDH enzyme complex (SDHA, SDHB, SDHC and SDHD). Together with a somatic second hit, these variants lead to the loss of function of the SDH complex. SDH-deficient RCC associated with SDHA mutation is a rare condition; to the best of our knowledge, there have been only four patients reported in the literature. The present study describes the case of a 22-year-old female patient with RCC associated with SDHA gene mutation. Next-generation sequencing and Sanger sequencing identified a novel heterozygous frameshift variant (NM_004168.4: c.992_999dup) in the SDHA gene. In the literature, this mutation has not previously been reported to be associated with RCC. The present description of a patient with a heterozygous SDHA frameshift variant expands the phenotypic spectrum of the SDHA gene, and provides further clinical, morphological and molecular data of SDHA-deficient RCC.

Morphological diversity in SDH-deficient renal carcinomas: a three-case exploration of variant features and dedifferentiation

Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is a rare subtype of renal neoplasm predominantly affecting younger individuals. It is characterized by germline mutations in SDHx genes, particularly type B. Histologically, SDH-deficient RCC features eosinophilic cytoplasmic cells forming solid nests or microcysts, sometimes entrapping normal tubules. We present three SDH-deficient RCC cases with overlapping morphological features with fumarate hydratase-deficient RCC and TFEB-rearranged RCC, an appearance that has not been previously described. All tumors lacked SDHB expression and harbored pathogenic SDHB mutations, with the germline nature confirmed in two cases. Metastasis developed in two patients. Our case set highlights the diagnostic challenges of molecularly defined renal tumors and expands the morphological spectrum of SDH-deficient RCC with unusual histological features. Clinically, these tumors appear to be aggressive.

Succinate Dehydrogenase Deficient Renal Cell Carcinoma With Sarcomatoid and Rhabdoid Features-A Diagnostic Dilemma

Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is a rare epithelial tumor with a biallelic mutation involving any subunit of the SDH complex. Mostly, it has low-grade morphology and a favorable prognosis. We present a case of a 36-year-old woman with weight loss, night sweats, and symptomatic anemia. Her imaging showed a hypo-enhancing heterogeneous right renal mass with invasion of the renal vein and inferior vena cava. Microscopically, the tumor had focal low-grade areas (5%) and extensive areas with high-grade features, including rhabdoid (85%) and sarcomatoid (10%) dedifferentiation. Cytoplasmic inclusions, foci of extracellular mucin, coagulative necrosis, and inflammatory infiltrate were present. The tumor cells, including rhabdoid differentiated, were focally positive for AE1/AE3. Tumor cells showed loss of SDHB immunostaining, consistent with diagnosis. Genetics testing was recommended, but the patient expired due to metastatic carcinoma. Prior studies suggest that sarcomatoid transformation and coagulative necrosis increase the risk of metastasis by up to 70% in SDH-deficient RCC. Follow-up with surveillance for other SDH-deficient neoplasms is recommended in cases of germline mutation. Here, we report the first case of SDH-deficient RCC with concomitant rhabdoid and sarcomatoid features and a detailed review of diagnostic difficulties associated with high-grade tumors.

Genomic profiling and molecular characterization of non-clear cell renal cell carcinoma: a narrative review from a clinical perspective

While the clear-cell renal cell carcinoma (ccRCC) treatment has undergone several paradigm shifts in recent years, the non-clear cell renal cell carcinoma (nccRCC) therapeutic approach has yet to be extensively investigated and improved. The WHO 2022 classification of renal neoplasms redefined the most common nccRCC subtypes (papillary and chromophobe RCC) and introduced the molecularly defined RCC class, which is a first step in the direction of better molecular profiling of nccRCC. We reviewed the literature data on known genomic alterations of clinical interest in nccRCC and discussed their potential role in guiding therapeutic choices in each nccRCC entity. Among the alterations discussed, we focused on the ones that could be treated with already available drugs, such as MET-driven papillary RCC, mechanistic target of rapamycin altered chromophobe RCC, anaplastic lymphoma kinase-rearranged RCC, and fumarate-hydratase deficient RCC. Furthermore, we focused on the currently ongoing clinical trials and further evidence for all the other entities, such as SMARCB1-deficient RCC, TFE3 and transcription factorEB (TFEB)-altered RCC, and Elongin C (ELOC)-mutated RCC. The vast heterogeneity of nccRCC does not allow a one-size-fits-all solution; therefore, molecular characterization is the path toward effective therapies and fully personalized medicine for these entities.

Imaging finding of renal masses associated with pathogenic variation in succinate dehydrogenase subunit B gene

PURPOSE

Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is a newly defined, rare subtype of renal cancer, associated with pathogenic variations in the Succinate Dehydrogenase Subunit B (SDHB) gene. Our aim is to investigate the imaging findings of SDHB-associated renal tumors, utilizing cross-sectional and FDG-PET imaging in patients with pathogenic variations in SDHB gene, to facilitate accurate tumor characterization.

METHODS

Twenty SDH-deficient tumors from 16 patients with pathogenic variations in SDHB gene were retrospectively evaluated using cross-sectional and FDG-PET imaging. Clinical findings such as demographics, family history, extra-renal findings and metastases were recorded. Tumor imaging characteristics on CT/MRI included were laterality, size, homogeneity, morphology, margins, internal content, T1/T2 signal intensity, enhancement features, and restricted diffusion.

RESULTS

Sixteen patients (median age 31 years, IQR 19-41, 8 males) were identified with 68.8 % of patients having a known family history of SDHB variation. 81.3 % of lesions were solitary and majority were solid (86.7 % on CT, 87.5 % on MRI) with well-defined margins in >62.5 % of lesions, without evidence of internal fat, calcifications, or vascular invasion. 100 % of lesions demonstrated restricted diffusion and avid enhancement, with degree >75 % for most lesions on CT and MRI. On FDG-PET, all renal masses showed increased radiotracer uptake. 43.8 % of patients demonstrated extra-renal manifestations and 43.8 % had distant metastasis.

CONCLUSION

SDHB-associated RCC is predominantly noted in young patients with no gender predilection. On imaging, SDH-deficient RCC are frequently unilateral, solitary, and solid with well-defined margins demonstrating avid enhancement with variability in enhancement pattern and showing restricted diffusion.

Keratin 20 positive SDH-deficient renal cell carcinoma: a case report and literature review

This study aims to broaden the morphological scope of SDH-deficient renal cell carcinoma and to assist clinicians and pathologists in better understanding this entity to prevent misdiagnosis. This study used immunohistochemistry staining and the first-generation sequencing Sanger method for gene detection. It retrospectively analysed the clinical pathology, molecular characteristics, biological behaviour, and treatment information of one case of SDH-deficient renal cell carcinoma. The patient was a 57-year-old female with right back pain for more than 20 days and had no personal or family history of kidney tumours. In addition, the tumour cells had clear boundaries in morphology, and residual normal renal tubules could be seen around them. There were also ossification and adipose tissue around the tumour centre. The tumour cells were arranged in a glandular tubular and cord-like manner. Vacuolar and eosinophilic inclusion bodies could be observed in the cytoplasm. The nucleus was regular, the chromatin distribution was fine, and there were no obvious nucleoli. They were low-grade nuclei. In addition, no atypical mitosis or necrosis could been found. Furthermore, immunohistochemistry staining showed SDHB-negative and keratin 20 -positive tumour. Meanwhile, the first-generation sequencing also pointed out the presence of SDHB gene mutations in the tumour. After 12 months of follow-up, there was no evidence of disease recurrence in the patient. SDH-deficient renal cell carcinoma is a rare tumour associated with SDH gene germline mutations, and suspected cases should undergo SDHB immunohistochemistry staining. Most SDH-deficient renal cell carcinomas have a good prognosis, but undifferentiated cases require long-term follow-up.

[Succinate Dehydrogenase-Deficient Renal Cell Carcinoma: Clinicopathological Analysis of 11 Cases]

Objective

To investigate the clinicopathological features, immunophenotypes, molecular genetic alterations, and prognosis of succinate dehydrogenase-deficient renal cell carcinoma (SDH-RCC).

Methods

A total of 11 cases of SDH-RCC diagnosed at West China Hospital, Sichuan University between 2016 and 2023 were selected for clinicopathological, immunohistochemical, and DNA sequencing analyses.

Results

Among the 11 cases of SDH-RCC, there were 5 male patients and 6 female patients. The patients' ages ranged from 12 to 71 years, with an average age of 39.7 years. Among them, 5 patients had tumors located in the right kidney, 5 had tumors located in the left kidney, and 1 patient had bilateral tumors. Microscopic observation showed that the tumor cells of the SDH-RCC patients displayed a wide spectrum of structures, forming sheet-like, nested, and glandular structures. In addition, tumor cells in papillary structures were observed in some cases. The tumor cells had abundant cytoplasm, was eosinophilic, and contained flocculent materials. Intracytoplasmic vacuolations were observed in some of the cells. Among all the patients, 7 (7/11, 63.6%) showed typical low-grade features (grade 1-2 according to the International Society of Urological Pathology [ISUP]/WHO 2016 classification), and 4 (4/11, 36.4%) showed high-grade features (grade 3 according to the ISUP/WHO 2016 classification). The average ages of patients with low-grade and high-grade features were 32.1 years and 58.0 years, respectively. Immunohistochemical staining of all 11 cases demonstrated negative results for SDHB and cytokeratin 7 (CK7), and positive staining results for paired box 8 (PAX-8), fumarate hydratase (FH), and epithelial membrane antigen (EMA). Their Ki-67 index was 1%-30%. In one case, the loss of SDHB expression was also accompanied by a loss of SDHA expression. Sanger sequencing was performed to examine all the exons of SDHB in 7 cases. One case showed a frameshift mutation, c.236Tdel (p.K80Rfs*), and another case harbored a missense mutation, c.725G>A (p.Arg242His). In another case, next generation sequencing revealed that large fragments of SDHB (Exon 4-8 del) were missing. Follow-up data were available for 10 patients. The follow-up time ranged from 4 to 138 months, with the average being 32.8 months, and all patients survived. Metastasis and recurrence were reported in 5 cases, with 3 of them showing high-grade features and 2 showing low-grade features.

Conclusion

SDH-RCC is rare and the patients demonstrate a relatively young age of onsets. Patients may present with bilateral tumors. Tumors with low-grade features usually occur in young patients, with their Ki-67 index usually being lower than 5%. Individual cases may experience tumor recurrence and metastasis over a long period of follow-up. Tumors with high-grade features tend to occur in older patients who have a higher Ki-67 index, and who are prone to recurrence and metastasis. Negative immunohistochemical staining results for SDHB can assist in tumor diagnosis, but the loss of SDHB protein expression does not necessarily lead to the detection of SDHB gene mutation.

Hereditary renal mass syndromes: a pictorial review

Hereditary renal mass syndromes, although rare, account for at least 3-5% of kidney cancers and significantly impact affected families. Accurate diagnosis and management by radiologists are crucial as these syndromes often present at imaging with both renal and extra-renal manifestations. The radiologist may be the first to recognize these stigmata at imaging, some of which satisfy major features for diagnosis and obviate the need for genetic testing. Furthermore, radiologists contribute to lifelong imaging surveillance and locoregional treatment. This pictorial review discusses the following major hereditary renal mass syndromes with their typical renal mass appearance, extrarenal manifestations, inheritance pattern, diagnosis, and management strategies based on the most recent National Comprehensive Cancer Network guidelines: Von Hippel-Lindau syndrome, tuberous sclerosis complex, Birt-Hogg-Dube syndrome, hereditary paraganglioma/pheochromocytoma (PGL/PCC) syndrome/succinate dehydrogenase deficiency, hereditary leiomyomatosis and renal cell cancer (HLRCC)/fumarate hydratase deficiency, PTEN hamartoma syndrome, BRCA1-associated protein 1 (BAP1) tumor disposition syndrome, hereditary papillary renal cell carcinoma, and familial clear cell renal cell cancer with chromosome 3 translocation.

Succinate dehydrogenase A deficient renal cell carcinoma: A rare renal tumor distinct from typical Succinate dehydrogenase deficient renal cell carcinoma

Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is a rare subtype of RCC classified as a molecularly defined RCC in the fifth edition of the WHO. Most gene alterations in patients with SDH-deficient RCC involve the SDHB subunit, with less involvement of the SDHC, SDHA, and SDHD subunits. Four cases of SDHA-deficient RCC have been reported in the literature, of which one case was associated with an NF2 gene mutation. Herein, we report six novel SDHA-deficient RCC cases, including two cases with NF2 gene mutations. In contrast to the typical morphology of SDH-deficient RCC, the six tumors mainly displayed glandular, sheet-like, or papillary growth patterns with prominent nucleoli (Grades 2-3), among which two cases with NF2 mutations had prominent nucleoli (Grade 3), large transparent vacuoles in the cytoplasm, and a large number of lymphocytes in the stroma. Six tumors showed negative immunohistochemical staining for SDHA and SDHB, and three cases presented with high expression of PD-L1. Second-generation sequencing revealed novel pathogenic somatic SDHA gene mutation and NF2 gene mutations in six and two tumors, respectively. Follow-up data were collected for the six patients with a follow-up time ranging from 7 to 268 months, and all six patients have survived to date. One patient received targeted therapy for tumor metastasis to the lungs after seven months, and another patient with an NF2 gene mutation received immunotherapy for lymph node metastasis revealed during surgery. SDHA-deficient RCCs with NF2 gene mutations have the ability to metastasize but might respond well to immunotherapy. For the first time, we report the largest number of SDHA-deficient RCC cases and comprehensively investigate their clinicopathological and molecular features to provide important guidance for diagnosis and clinical immunotherapy.

Molecular Genetics of Pheochromocytoma/Paraganglioma

Pheochromocytomas and paragangliomas (PPGL) are neuroendocrine tumors which secrete catecholamines, causing cardiovascular compromise. While isolated tumors and locoregional disease can be treated surgically, treatment options for metastatic disease are limited, and no targeted therapies exist. Approximately 25% of PPGL are causatively associated with germline pathogenic variants, which are known risk factors for multifocal and metastatic PPGL. Knowledge of somatic driver mutations continues to evolve. Molecular classification of PPGL has identified three genomic subtypes: Cluster 1 (pseudohypoxia), Cluster 2 (kinase signaling) and Cluster 3 (Wnt-altered). This review summaries recent studies characterizing the tumor microenvironment, genomic drivers of tumorigenesis and progression, and current research on molecular targets for novel diagnostic and therapeutic strategies in PPGL.

Advances in Molecular Mechanisms of Kidney Disease: Integrating Renal Tumorigenesis of Hereditary Cancer Syndrome

Renal cell carcinoma (RCC) comprises various histologically distinct subtypes, each characterized by specific genetic alterations, necessitating individualized management and treatment strategies for each subtype. An exhaustive search of the PubMed database was conducted without any filters or restrictions. Inclusion criteria encompassed original English articles focusing on molecular mechanisms of kidney cancer. On the other hand, all non-original articles and articles published in any language other than English were excluded. Hereditary kidney cancer represents 5-8% of all kidney cancer cases and is associated with syndromes such as von Hippel-Lindau syndrome, Birt-Hogg-Dubè syndrome, succinate dehydrogenase-deficient renal cell cancer syndrome, tuberous sclerosis complex, hereditary papillary renal cell carcinoma, fumarate hydratase deficiency syndrome, BAP1 tumor predisposition syndrome, and other uncommon hereditary cancer syndromes. These conditions are characterized by distinct genetic mutations and related extra-renal symptoms. The majority of renal cell carcinoma predispositions stem from loss-of-function mutations in tumor suppressor genes. These mutations promote malignant advancement through the somatic inactivation of the remaining allele. This review aims to elucidate the main molecular mechanisms underlying the pathophysiology of major syndromes associated with renal cell carcinoma. By providing a comprehensive overview, it aims to facilitate early diagnosis and to highlight the principal therapeutic options available.

A highly malignant succinate dehydrogenase A‑deficient renal cell carcinoma with bone metastasis misdiagnosed as hereditary leiomyomatosis and renal cell carcinoma: A case report

Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is an autosomal dominant syndrome caused by heterozygous pathogenic germline variants of the SDH gene. SDH mutations are associated with an increased risk of developing RCC, although studies describing SDH-deficient RCC are currently limited. The present study reported a case of SDH-deficient RCC with high malignancy and rare bone metastasis. The patient was diagnosed with a right renal mass through B-mode ultrasound imaging and showed a carcinoma embolus in the right renal vein and inferior vena cava through kidney contrast-enhanced computed tomography. A whole-body bone scan showed radionuclide accumulation in the upper end of the left humerus, which indicated possible pathological bone destruction. As a result, surgical resection was performed. The postoperative pathology indicated a high-grade RCC and although the specific classification remained uncertain, hereditary leiomyomatosis and RCC was suspected. Subsequently, a germline mutation of the succinate dehydrogenase complex flavoprotein subunit A gene was identified through high-throughput sequencing (c.1A>G, p. Met1?) and immunohistochemistry demonstrated the loss of succinate dehydrogenase complex flavoprotein subunit B expression. Postoperatively, the patient underwent radiotherapy and targeted therapy. After 6 months of follow-up treatment, there was no indication of recurrence or metastasis on thoracoabdominal CT and whole-body bone scintigraphy. Based on the present report, germline screening should potentially be encouraged in early-onset patients as family history or pathological results may not provide sufficient information for the early, differential diagnosis of SDH-deficient RCC.

The New WHO Category of "Molecularly Defined Renal Carcinomas": Clinical and Diagnostic Features and Management Implications

The evolution of classification of renal tumors has been impacted since the turn of the millennium by rapid progress in histopathology, immunohistochemistry, and molecular genetics. Together, these features have enabled firm recognition of specific, classic types of renal cell carcinomas, such as clear cell renal cell carcinoma, that in current practice trigger histologic-type specific management and treatment protocols. Now, the fifth Edition World Health Classification's new category of "Molecularly defined renal carcinomas" changes the paradigm, defining a total of seven entities based specifically on their fundamental molecular underpinnings. These tumors, which include TFE3-rearranged, TFEB-altered, ELOC-mutated, fumarate hydratase-deficient, succinate dehydrogenase-deficient, ALK-rearranged, and SMARCB1-deficient renal medullary carcinoma, encompass a wide clinical and histopathologic phenotypic spectrum of tumors. Already, important management aspects are apparent for several of these entities, while emerging therapeutic angles are coming into view. A brief, clinically-oriented introduction of the entities in this new category, focusing on relevant diagnostic, molecular, and management aspects, is the subject of this review.

The Prevalence and Radiologic Features of Renal Cancers Associated with FLCN, BAP1, SDH, and MET Germline Mutations

Purpose To investigate the prevalence of FLCN, BAP1, SDH, and MET mutations in an oncologic cohort and determine the prevalence, clinical features, and imaging features of renal cell carcinoma (RCC) associated with these mutations. Secondarily, to determine the prevalence of encountered benign renal lesions. Materials and Methods From 25 220 patients with cancer who prospectively underwent germline analysis with a panel of more than 70 cancer-predisposing genes from 2015 to 2021, patients with FLCN, BAP1, SDH, or MET mutations were retrospectively identified. Clinical records were reviewed for patient age, sex, race/ethnicity, and renal cancer diagnosis. If RCC was present, baseline CT and MRI examinations were independently assessed by two radiologists. Summary statistics were used to summarize continuous and categorical variables by mutation. Results A total of 79 of 25 220 (0.31%) patients had a germline mutation: FLCN, 17 of 25 220 (0.07%); BAP1, 22 of 25 220 (0.09%); SDH, 39 of 25 220 (0.15%); and MET, one of 25 220 (0.004%). Of these 79 patients, 18 (23%) were diagnosed with RCC (FLCN, four of 17 [24%]; BAP1, four of 22 [18%]; SDH, nine of 39 [23%]; MET, one of one [100%]). Most hereditary RCCs demonstrated ill-defined margins, central nonenhancing area (cystic or necrotic), heterogeneous enhancement, and various other CT and MR radiologic features, overlapping with the radiologic appearance of nonhereditary RCCs. The prevalence of other benign solid renal lesions (other than complex cysts) in patients was up to 11%. Conclusion FLCN, BAP1, SDH, and MET mutations were present in less than 1% of this oncologic cohort. Within the study sample size limits, imaging findings for hereditary RCC overlapped with those of nonhereditary RCC, and the prevalence of other associated benign solid renal lesions (other than complex cysts) was up to 11%. Keywords: Familial Renal Cell Carcinoma, Birt-Hogg-Dubé Syndrome, Carcinoma, Renal Cell, Paragangliomas, Urinary, Kidney © RSNA, 2024.

Acquired cystic disease-associated renal cell carcinoma with PTCH1 mutation: a case report

Acquired cystic disease-associated renal cell carcinoma (ACD-RCC) is an extremely rare kidney tumor seen mainly in patients with end-stage renal disease. Currently, there are few reports on this type of tumor. We describe the case of a 58-year-old man who had been receiving peritoneal dialysis for more than nine years due to chronic renal insufficiency and uremia. One year after undergoing left renal clear cell renal cell carcinoma resection, a space-occupying lesion was found in the right kidney for which he underwent right nephrectomy. The histopathology of this tumor showed solid or tubular cell arrangements, with some areas of cyst formation. Vacuoles of varying sizes were present in the cytoplasm, and varying amounts of calcium oxalate crystals were found in the tumor cells or interstitium. The pathological diagnosis was ACD-RCC. Next-generation sequencing detected mutations in the PTCH1, MTOR, FAT1, SOS1, RECQL4, and CDC73 genes in the right renal tumor. This is a rare case of a patient with ACD-RCC in the right kidney and clear cell renal cell carcinoma in the left kidney. The findings suggest that mutations in PTCH1 associated with ACD-RCC may have acted as oncogenic drivers for the development of ACKD-RCC, together with providing insight into mechanisms underlying ACD-RCC development, as well as diagnostic and treatment options.

The Application and Pitfalls of Immunohistochemical Markers in Challenging Diagnosis of Genitourinary Pathology

CONTEXT.—

The morphologic features of different entities in genitourinary pathology overlap, presenting a diagnostic challenge, especially when diagnostic materials are limited. Immunohistochemical markers are valuable when morphologic features alone are insufficient for definitive diagnosis. The World Health Organization classification of urinary and male genital tumors has been updated for 2022. An updated review of immunohistochemical markers for newly classified genitourinary neoplasms and their differential diagnosis is needed.

OBJECTIVE.—

To review immunohistochemical markers used in the diagnosis of genitourinary lesions in the kidney, bladder, prostate, and testis. We particularly emphasized difficult differential diagnosis and pitfalls in immunohistochemistry application and interpretation. New markers and new entities in the 2022 World Health Organization classifications of genitourinary tumors are reviewed. Recommended staining panels for commonly encountered difficult differential diagnoses and potential pitfalls are discussed.

DATA SOURCES.—

Review of current literature and our own experience.

CONCLUSIONS.—

Immunohistochemistry is a valuable tool in the diagnosis of problematic lesions of the genitourinary tract. However, the immunostains must be carefully interpreted in the context of morphologic findings with a thorough knowledge of pitfalls and limitations.

Hereditary succinate dehydrogenase-deficient renal cell carcinoma

Succinate dehydrogenase (SDH), formed by four subunits SDHA, SDHB, SDHC, SDHD, and an assembly factor SDHAF2, functions as a key respiratory enzyme. Biallelic inactivation of genes encoding any of the components, almost always in the presence of a germline mutation, causes loss of function of the entire enzyme complex (so-called SDH deficiency) and subsequent development of SDH-deficient neoplasms which include pheochromocytoma/paraganglioma, gastrointestinal stromal tumor, and renal cell carcinoma (RCC). These tumors may occur in the same patient or kindred. SDH-deficient RCC shows distinctive morphological features with vacuolated eosinophilic cytoplasm due to distinctive cytoplasmatic inclusions containing flocculent material. The diagnosis is confirmed by loss of SDHB on immunohistochemistry with positive internal control. The majority of tumors occur in the setting of germline mutations in one of the SDH genes, most commonly SDHB. The prognosis is excellent for low-grade tumors but worse for high-grade tumors with high-grade nuclei, sarcomatoid change, or coagulative necrosis. Awareness of the morphological features and low-threshold for applying SDHB immunohistochemistry help identify patients with SDH-deficient RCC and hereditary SDH-deficient tumor syndromes. In this review we summarize recent development on the clinical and genetic features, diagnostic approach, and pitfalls of SDH-deficient syndrome, focusing on SDH-deficient renal cell carcinomas.

mTOR eosinophilic renal cell carcinoma: a distinctive tumor characterized by mTOR mutation, loss of chromosome 1, cathepsin-K expression, and response to target therapy

In the spectrum of oncocytic renal neoplasms, a subset of tumors with high-grade-appearing histologic features harboring pathogenic mutations in mammalian target of rapamycin (mTOR) and hitherto clinical indolent behavior has been described. Three cases (2F,1 M) with histologically documented metastases (lymph node, skull, and liver) were retrieved and extensively investigated by immunohistochemistry, FISH, and next-generation sequencing. Tumors were composed of eosinophilic cells with prominent nucleoli (G3 by ISUP/WHO) arranged in solid to nested architecture. Additionally, there were larger cells with perinuclear cytoplasmic shrinkage and sparse basophilic Nissl-like granules, superficially resembling the so-called spider cells of cardiac rhabdomyomas. The renal tumors, including the skull and liver metastases, showed immunoexpression PAX8, CK8-18, and cathepsin-K, and negativity for vimentin. NGS identified mTOR genetic alterations in the three cases, including the skull and liver metastases. One patient was then treated with Everolimus (mTOR inhibitors) with clinical response (metastatic tumor shrinkage). We present a distinct renal tumor characterized by high-grade eosinophilic cells, cathepsin-K immunohistochemical expression, and harboring mTOR gene mutations demonstrating a malignant potential and showing responsiveness to mTOR inhibitors.

Research progress on the pathogenesis of the SDHB mutation and related diseases

With the improvement of genetic testing technology in diseases in recent years, researchers have a more detailed and clear understanding of the source of cancers. Succinate dehydrogenase B (SDHB), a mitochondrial gene, is related to the metabolic activities of cells and tissues throughout the body. The mutations of SDHB have been found in pheochromocytoma, paraganglioma and other cancers, and is proved to affect the occurrence and progress of those cancers due to the important structural functions. The importance of SDHB is attracting more and more attention of researchers, however, reviews on the structure and function of SDHB, as well as on the mechanism of its carcinogenesis is inadequate. This paper reviews the relationship between SDHB mutations and related cancers, discusses the molecular mechanism of SDHB mutations that may lead to tumor formation, analyzes the mutation spectrum, structural domains, and penetrance of SDHB and sorts out some of the previously discovered diseases. For the patients with SDHB mutation, it is recommended that people in SDHB mutation families undergo regular genetic testing or SDHB immunohistochemistry (IHC). The purpose of this paper is hopefully to provide some reference and help for follow-up researches on SDHB.

SDHi fungicides: An example of mitotoxic pesticides targeting the succinate dehydrogenase complex

Succinate dehydrogenase inhibitors (SDHi) are fungicides used to control the proliferation of pathogenic fungi in crops. Their mode of action is based on blocking the activity of succinate dehydrogenase (SDH), a universal enzyme expressed by all species harboring mitochondria. The SDH is involved in two interconnected metabolic processes for energy production: the transfer of electrons in the mitochondrial respiratory chain and the oxidation of succinate to fumarate in the Krebs cycle. In humans, inherited SDH deficiencies may cause major pathologies including encephalopathies and cancers. The cellular and molecular mechanisms related to such genetic inactivation have been well described in neuroendocrine tumors, in which it induces an oxidative stress, a pseudohypoxic phenotype, a metabolic, epigenetic and transcriptomic remodeling, and alterations in the migration and invasion capacities of cancer cells, in connection with the accumulation of succinate, an oncometabolite, substrate of the SDH. We will discuss recent studies reporting toxic effects of SDHi in non-target organisms and their implications for risk assessment of pesticides. Recent data show that the SDH structure is highly conserved during evolution and that SDHi can inhibit SDH activity in mitochondria of non-target species, including humans. These observations suggest that SDHi are not specific inhibitors of fungal SDH. We hypothesize that SDHi could have toxic effects in other species, including humans. Moreover, the analysis of regulatory assessment reports shows that most SDHi induce tumors in animals without evidence of genotoxicity. Thus, these substances could have a non-genotoxic mechanism of carcinogenicity that still needs to be fully characterized and that could be related to SDH inhibition. The use of pesticides targeting mitochondrial enzymes encoded by tumor suppressor genes raises questions on the risk assessment framework of mitotoxic pesticides. The issue of SDHi fungicides is therefore a textbook case that highlights the urgent need for changes in regulatory assessment.

Succinate dehydrogenase deficient renal cell carcinoma: A case report of an uncommon renal cancer

Succinate dehydrogenase-deficient renal cell carcinoma (SDH-deficient RCC) is a rare type of renal cancer with distinct morphological features and diagnostic immunohistochemistry characterized by the absence of SDH immunostaining. The pathologists and the clinician need to be aware of this entity in view of their indolent course in most cases. We present here the first case from India of SDHB-deficient RCC.

Succinate Dehydrogenase Defects Giant Renal Cell Carcinoma

Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is a new subtype of RCC included in the 2016 edition of the WHO classification in RCC. SDH-defective RCC accounts for 0.05-0.2%, and preoperative diagnosis is difficult. We report a severe adherent RCC of inferior vena cava that underwent open radical nephrectomy after preoperative renal artery embolization. Postoperative histopathological examination diagnosed SDH-defective RCC; the clinicopathological stage was pT2b. After 10 months of follow-up, the patient had no evidence of disease recurrence. For patients with large RCC, interventional embolization can be selected to reduce intraoperative bleeding and blood transfusion, and it is recommended to complete interventional surgery within 3-4 h before surgery. SDH-deficient RCC is difficult to distinguish from other renal tumors in imaging, so immunohistochemical examination of SDHB is recommended for young and middle-aged patients, especially those under 45.

Recent Advances in the Management of Clear Cell Renal Cell Carcinoma: Novel Biomarkers and Targeted Therapies

Renal cell carcinoma (RCC) belongs to a heterogenous cancer group arising from renal tubular epithelial cells. Among RCC subtypes, clear cell renal cell carcinoma (ccRCC) is the most common variant, characterized by high aggressiveness, invasiveness and metastatic potential, features that lead to poor prognosis and high mortality rate. In addition, diagnosis of kidney cancer is incidental in the majority of cases, and this results in a late diagnosis, when the stage of the disease is advanced and the tumor has already metastasized. Furthermore, ccRCC treatment is complicated by its strong resistance to chemo- and radiotherapy. Therefore, there is active ongoing research focused on identifying novel biomarkers which could be useful for assessing a better prognosis, as well as new molecules which could be used for targeted therapy. In this light, several novel targeted therapies have been shown to be effective in prolonging the overall survival of ccRCC patients. Thus, the aim of this review is to analyze the actual state-of-the-art on ccRCC diagnosis, prognosis and therapeutic options, while also reporting the recent advances in novel biomarker discoveries, which could be exploited for a better prognosis or for targeted therapy.

Clinical Characteristics of Molecularly Defined Renal Cell Carcinomas

Kidney tumors comprise a broad spectrum of different histopathological entities, with more than 0.4 million newly diagnosed cases each year, mostly in middle-aged and older men. Based on the description of the 2022 World Health Organization (WHO) classification of renal cell carcinoma (RCC), some new categories of tumor types have been added according to their specific molecular typing. However, studies on these types of RCC are still superficial, many types of these RCC currently lack accurate diagnostic standards in the clinic, and treatment protocols are largely consistent with the treatment guidelines for clear cell RCC (ccRCC), which might result in worse treatment outcomes for patients with these types of molecularly defined RCC. In this article, we conduct a narrative review of the literature published in the last 15 years on molecularly defined RCC. The purpose of this review is to summarize the clinical features and the current status of research on the detection and treatment of molecularly defined RCC.

Diseases of Hereditary Renal Cell Cancers

Germline mutations in tumor suppressor genes and oncogenes lead to hereditary renal cell carcinoma (HRCC) diseases, characterized by a high risk of RCC and extrarenal manifestations. Patients of young age, those with a family history of RCC, and/or those with a personal and family history of HRCC-related extrarenal manifestations should be referred for germline testing. Identification of a germline mutation will allow for testing of family members at risk, as well as personalized surveillance programs to detect the early onset of HRCC-related lesions. The latter allows for more targeted and therefore more effective therapy and better preservation of renal parenchyma.

Recurrent CYP2A6 gene mutation in biphasic hyalinizing psammomatous renal cell carcinoma: Additional support of three cases

Biphasic hyalinizing psammomatous renal cell carcinoma (BHP RCC) with NF2 gene mutations is a newly described provisional category of renal cell carcinoma (RCC). Here we described three additional cases of BHP RCC with CYP2A6 gene mutation besides NF2 gene. The carcinomas were predominantly unencapsulated, and two of them had a rounded, nodular interface with the native kidney while one had perirenal adipose tissue invasion. Histopathologically, all neoplasms had a characteristic biphasic appearance of smaller cells clustering around basement membrane material within larger acini, forming pseudorosettes or a glomeruloid pattern. The smaller cells were focally spindle-shaped in two carcinomas. Psammoma bodies were shown in two carcinomas. Cellular necrosis and perineural invasion was identified in one case. Immunohistochemically, Vimentin, EMA, P504s were extensively expressed while RCC and CD10 were only expressed in larger cells. CK7 was positive in one tumor. CYP2A6 gene mutation (CYP2A6 NM_000762.6: exon4:c.A580G:p.K194E) was revealed in three tumors by Whole-genome exome sequencing, which was further confirmed by Sanger sequencing. Only one case harbored a somatic termination mutation in NF2 gene. NF2 promoter methylation was observed in the other two cases. Clinically, one patient died of disease with widespread bone metastases confirmed by biopsy at the ninth month after surgery but the other two patients had no evidence of recurrence or metastases (follow-up period 9-90 months). Our findings validated previously described clinicopathological features and NF2 gene mutation or promoter methylation of BHP RCC. In addition, we reported different IHC pattern of BHP RCC and further revealed the recurrent CYP2A6 genetic alteration.

Clinico-pathological implications of the 2022 WHO Renal Cell Carcinoma classification

The new WHO classification of urogenital tumours published in 2022, contains significant revisions upon the previous 2016 version regarding Renal Cell Carcinoma (RCC). While the most common histotype remains almost untouched, some of the main novelties concerns papillary RCC and oncocytic neoplasms. The main change is the introduction of a new category of molecularly-defined RCC, which includes TFE3-rearranged RCC, TFEB-rearranged, and TFEB-amplified RCC, FH-deficient RCC, SDH-deficient RCC, ALK-rearranged RCC, ELOC (formerly TCEB1)-mutated RCC, SMARCB1 (INI1)-deficient RCC. In this paper we analyze the current knowledge on emerging entities and molecularly-defined RCC to assess whether the current pathological classification offers the oncologist the possibility of selecting more specific and personalized treatments, from both those currently available, as well as those that will soon be available.

SDHx mutation and pituitary adenoma: can in vivo 1H-MR spectroscopy unravel the link?

Germline mutations in genes encoding succinate dehydrogenase (SDH) are frequently involved in pheochromocytoma/paraganglioma (PPGL) development and were implicated in patients with the '3PAs' syndrome (associating pituitary adenoma (PA) and PPGL) or isolated PA. However, the causality link between SDHx mutation and PA remains difficult to establish, and in vivo tools for detecting hallmarks of SDH deficiency are scarce. Proton magnetic resonance spectroscopy (1H-MRS) can detect succinate in vivo as a biomarker of SDHx mutations in PGL. The objective of this study was to demonstrate the causality link between PA and SDH deficiency in vivo using 1H-MRS as a novel noninvasive tool for succinate detection in PA. Three SDHx-mutated patients suffering from a PPGL and a macroprolactinoma and one patient with an apparently sporadic non-functioning pituitary macroadenoma underwent MRI examination at 3 T. An optimized 1H-MRS semi-LASER sequence (TR = 2500 ms, TE = 144 ms) was employed for the detection of succinate in vivo. Succinate and choline-containing compounds were identified in the MR spectra as single resonances at 2.44 and 3.2 ppm, respectively. Choline compounds were detected in all the tumors (three PGL and four PAs), while a succinate peak was only observed in the three macroprolactinomas and the three PGL of SDHx-mutated patients, demonstrating SDH deficiency in these tumors. In conclusion, the detection of succinate by 1H-MRS as a hallmark of SDH deficiency in vivo is feasible in PA, laying the groundwork for a better understanding of the biological link between SDHx mutations and the development of these tumors.

Kidney tumors associated with germline mutations of FH and SDHB show a CpG island methylator phenotype (CIMP)

Germline mutations within the Krebs cycle enzyme genes fumarate hydratase (FH) or succinate dehydrogenase (SDHB, SDHC, SDHD) are associated with an increased risk of aggressive and early metastasizing variants of renal cell carcinoma (RCC). These RCCs express significantly increased levels of intracellular fumarate or succinate that inhibit 2-oxoglutarate-dependent dioxygenases, such as the TET enzymes that regulate DNA methylation. This study evaluated the genome-wide methylation profiles of 34 RCCs from patients with RCC susceptibility syndromes and 11 associated normal samples using the Illumina HumanMethylation450 BeadChip. All the HLRCC (FH mutated) and SDHB-RCC (SDHB mutated) tumors demonstrated a distinct CpG island methylator phenotype (CIMP). HLRCC tumors demonstrated an extensive and relatively uniform level of hypermethylation that showed some correlation with tumor size. SDHB-RCC demonstrated a lesser and more varied pattern of hypermethylation that overlapped in part with the HLRCC hypermethylation. Combined methylation and mRNA expression analysis of the HLRCC tumors demonstrated hypermethylation and transcription downregulation of genes associated with the HIF pathway, HIF3A and CITED4, the WNT pathway, SFRP1, and epithelial-to-mesenchymal transition and MYC expression, OVOL1. These observations were confirmed in the TCGA CIMP-RCC tumors. A selected panel of probes could identify the CIMP tumors and differentiate between HLRCC and SDHB-RCC tumors. This panel accurately detected all CIMP-RCC tumors within the TCGA RCC cohort, identifying them as HLRCC -like, and could potentially be used to create a liquid biopsy-based screening tool. The CIMP signature in these aggressive tumors could provide both a useful biomarker for diagnosis and a target for novel therapies.

Defining the origin, evolution, and immune composition of SDH-deficient renal cell carcinoma

Succinate dehydrogenase (SDH)-deficient renal cell carcinoma represents a rare subtype of hereditary kidney cancer. Clinical diagnosis can be challenging and there is little evidence to guide systemic therapeutic options. We performed genomic profiling of a cohort of tumors through the analysis of whole genomes, transcriptomes, as well as flow cytometry and immunohistochemistry in order to gain a deeper understanding of their molecular biology. We find neutral evolution after early tumor activation with a lack of secondary driver events. We show that these tumors have epithelial derivation, possibly from the macula densa, a specialized paracrine cell of the renal juxtaglomerular apparatus. They subsequently develop into immune excluded tumors. We provide transcriptomic and protein expression evidence of a highly specific tumor marker, PAPPA2. These translational findings have implications for the diagnosis and treatment for this rare tumor subtype.

Tumorigenesis Mechanisms Found in Hereditary Renal Cell Carcinoma: A Review

Renal cell carcinoma is a heterogenous cancer composed of an increasing number of unique subtypes each with their own cellular and tumor behavior. The study of hereditary renal cell carcinoma, which composes just 5% of all types of tumor cases, has allowed for the elucidation of subtype-specific tumorigenesis mechanisms that can also be applied to their sporadic counterparts. This review will focus on the major forms of hereditary renal cell carcinoma and the genetic alterations contributing to their tumorigenesis, including von Hippel Lindau syndrome, Hereditary Papillary Renal Cell Carcinoma, Succinate Dehydrogenase-Deficient Renal Cell Carcinoma, Hereditary Leiomyomatosis and Renal Cell Carcinoma, BRCA Associated Protein 1 Tumor Predisposition Syndrome, Tuberous Sclerosis, Birt-Hogg-Dubé Syndrome and Translocation RCC. The mechanisms for tumorigenesis described in this review are beginning to be exploited via the utilization of novel targets to treat renal cell carcinoma in a subtype-specific fashion.

Contemporary Clinical Definitions, Differential Diagnosis, and Novel Predictive Tools for Renal Cell Carcinoma

Despite significant progress regarding clinical detection/imaging evaluation modalities and genetic/molecular characterization of pathogenesis, advanced renal cell carcinoma (RCC) remains an incurable disease and overall RCC mortality has been steadily rising for decades. Concomitantly, clinical definitions have been greatly nuanced and refined. RCCs are currently viewed as a heterogeneous series of cancers, with the same anatomical origin, but fundamentally different metabolisms and clinical behaviors. Thus, RCC pathological diagnosis/subtyping guidelines have become increasingly intricate and cumbersome, routinely requiring ancillary studies, mainly immunohistochemistry. Meanwhile, RCC-associated-antigen targeted systemic therapy has been greatly diversified and emerging, novel clinical applications for RCC immunotherapy have already reported significant survival benefits, at least in the adjuvant setting. Even so, systemically disseminated RCCs still associate very poor clinical outcomes, with currently available therapeutic modalities only being able to prolong survival. In lack of a definitive cure for advanced RCCs, integration of the amounting scientific knowledge regarding RCC pathogenesis into RCC clinical management has been paramount for improving patient outcomes. The current review aims to offer an integrative perspective regarding contemporary RCC clinical definitions, proper RCC clinical work-up at initial diagnosis (semiology and multimodal imaging), RCC pathological evaluation, differential diagnosis/subtyping protocols, and novel clinical tools for RCC screening, risk stratification and therapeutic response prediction.

Succinate dehydrogenase-deficient malignant paraganglioma complicated by succinate dehydrogenase-deficient renal cell carcinoma

INTRODUCTION

SDH Gene mutation is known to be a common cause of pheochromocytoma/paraganglioma and renal cell carcinoma. Here, we report a case of succinate dehydrogenase B-deficient paraganglioma, which has a high risk of metastasis and recurrence, complicated by succinate dehydrogenase-deficient renal cell carcinoma, which is rare and accounts for approximately 0.1% of all renal cell carcinomas.

CASE PRESENTATION

A 50-year-old man underwent en bloc resection of a retroperitoneal tumor and the right kidney for retroperitoneal paraganglioma and right renal tumor. Both tumors showed negative expressions of succinate dehydrogenase B in immunostaining. The patient was diagnosed with succinate dehydrogenase-deficient paraganglioma and succinate dehydrogenase-deficient renal cell carcinoma. Seventeen months later, retroperitoneal lymphadenectomy revealed lymph node metastasis of the paraganglioma. Deletion of the SDHB gene was revealed by genome sequencing of the lymph node.

CONCLUSION

This is the first reported case of synchronously diagnosed succinate dehydrogenase-deficient paraganglioma and succinate dehydrogenase-deficient renal cell carcinoma.

Epidemiology of Renal Cell Carcinoma: 2022 Update

CONTEXT

International variations in the rates of kidney cancer (KC) are considerable. An understanding of the risk factors for KC development is necessary to generate opportunities to reduce its incidence through prevention and surveillance.

OBJECTIVE

To retrieve and summarize global incidence and mortality rates of KC and risk factors associated with its development, and to describe known familial syndromes and genetic alterations that represent biologic risk factors.

EVIDENCE ACQUISITION

A systematic review was conducted via Medline (PubMed) and Scopus to include meta-analyses, reviews, and original studies regarding renal cell carcinoma, epidemiology, and risk factors.

EVIDENCE SYNTHESIS

Our narrative review provides a detailed analysis of KC incidence and mortality, with significant variations across time, geography, and sex. In particular, while KC incidence has continued to increase, mortality models have leveled off. Among the many risk factors, hypertension, obesity, and smoking are the most well established. The emergence of new genetic data coupled with observational data allows for integrated management and surveillance strategies for KC care.

CONCLUSIONS

KC incidence and mortality rates vary significantly by geography, sex, and age. Associations of the development of KC with modifiable and fixed risk factors such as obesity, hypertension, smoking, and chronic kidney disease (CKD)/end-stage kidney disease (ESKD) are well described. Recent advances in the genetic characterization of these cancers have led to a better understanding of the germline and somatic mutations that predispose patients to KC development, with potential for identification of therapeutic targets that may improve outcomes for these at-risk patients.

PATIENT SUMMARY

We reviewed evidence on the occurrence of kidney cancer (KC) around the world. Currently, the main avoidable causes are smoking, obesity, and high blood pressure. Although other risk factors also contribute, prevention and treatment of these three factors provide the best opportunities to reduce the risk of developing KC at present.

Low grade oncocytic tumors of the kidney: a clinically relevant approach for the workup and accurate diagnosis

Renal oncocytoma and chromophobe renal cell carcinoma were accepted as unique renal tumors in the late 1990s. Since their formal description, criteria for diagnosis have evolved and additional distinct tumor subtypes originally considered as one these two entities are now recognized. The last two decades have witnessed unprecedented interest in the spectrum of low grade oncocytic renal neoplasms in three specific areas: (1) histologic characterization of tumors with overlapping morphologic features between oncocytoma and chromophobe renal cell carcinoma; (2) description of potentially unique entities within this spectrum, such as eosinophilic vacuolated tumor and low-grade oncocytic tumor; and (3) better appreciation of the association between a subset of low grade oncocytic tumors and hereditary renal neoplasia. While this important work has been academically rewarding, the proposal of several histologic entities with overlapping morphologic and immunophenotypic features (which may require esoteric adjunctive immunohistochemical and/or molecular techniques for confirmation) has created frustration in the diagnostic pathology and urology community as information evolves regarding classification within this spectrum of renal neoplasia. Pathologists, including genitourinary subspecialists, are often uncertain as to the "best practice" diagnostic approach to such tumors. In this review, we present a practical clinically relevant algorithmic approach to classifying tumors within the low grade oncocytic family of renal neoplasia, including a proposal for compressing terminology for evolving categories where appropriate without sacrificing prognostic relevance.

WHO 2022 landscape of papillary and chromophobe renal cell carcinoma

The 5th edition of the WHO Classification of Tumours of the Urinary and Male Genital Systems contains relevant revisions and introduces a group of molecularly defined renal tumour subtypes. Herein we present the World Health Organization (WHO) 2022 perspectives on papillary and chromophobe renal cell carcinoma with emphasis on their evolving classification, differential diagnosis, and emerging entities. The WHO 2022 classification eliminated the type 1/2 papillary renal cell carcinoma (pRCC) subcategorization, given the recognition of frequent mixed tumour phenotypes and the existence of entities with a different molecular background within the type 2 pRCC category. Additionally, emerging entities such as biphasic squamoid alveolar RCC, biphasic hyalinising psammomatous RCC, papillary renal neoplasm with reverse polarity, and Warthin-like pRCC are included as part of the pRCC spectrum, while additional morphological and molecular data are being gathered. In addition to oncocytomas and chromophobe renal cell carcinoma (chRCC), a category of 'other oncocytic tumours' with oncocytoma/chRCC-like features has been introduced, including emerging entities, most with TSC/mTOR pathway alterations (eosinophilic vacuolated tumour and so-called 'low-grade' oncocytic tumour), deserving additional research. Eosinophilic solid and cystic RCC was accepted as a new and independent tumour entity. Finally, a highly reproducible and clinically relevant universal grading system for chRCC is still missing and is another niche of ongoing investigation. This review discusses these developments and highlights emerging morphological and molecular data relevant for the classification of renal cell carcinoma.

Genomic and Metabolic Hallmarks of SDH- and FH-deficient Renal Cell Carcinomas

BACKGROUND

Succinate dehydrogenase-deficient and fumarate hydratase-deficient renal cell carcinomas (SDHRCC and FHRCC) are rare kidney cancers driven by loss of TCA cycle enzymes.

OBJECTIVE

To define and compare the genomic and metabolomic hallmarks of SDHRCC and FHRCC.

DESIGN, SETTING, AND PARTICIPANTS

We analyzed SDHRCC and FHRCC tumors with either immunohistochemical evidence of loss of protein expression or genomically confirmed biallelic inactivation of SDHA/B/C/D/AF2 or FH.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Somatic alterations were identified using clinical pipelines, with allele-specific copy number alterations (CNAs) identified using FACETS. Mass spectrometry-based metabolomic profiling was performed on available SDHRCC and FHRCC tumors.

RESULTS AND LIMITATIONS

Tumors were analyzed for 42 patients (25 FHRCC, 17 SDHRCC). In the germline analysis, 16/17 SDHRCCs harbored a germline alteration in SDHB, whereas only 17/22 FHRCCs had pathogenic germline FH variants. SDHRCCs had a lower mutation burden (p = 0.02) and CNA burden (p = 0.0002) than FHRCCs. All SDHRCCs presented with deletion of chromosome 1p (overlapping SDHB), whereas FHRCCs demonstrated high but not ubiquitous loss of 1q (FH locus). Both SDHRCCs and FHRCCs exhibited significant idiopathic accumulation of the metabolite guanine. FHRCC tumors had elevated levels of urea cycle metabolites (argininosuccinate, citrulline, and fumarate), whereas SDHRCC tumors had elevation of numerous acylcarnitines. These characteristic metabolic changes allowed identification of a previously unrecognized SDH-deficient RCC.

CONCLUSIONS

Despite sharing similar genetic etiology, SDHRCC and FHRCC represent distinct molecular entities with unique genetic and metabolic abnormalities.

PATIENT SUMMARY

Kidney cancers driven by loss of the gene encoding either the succinate dehydrogenase or fumarate hydratase enzyme are rare. We sought to define and compare the genetic and metabolic features of these cancer entities.

Papillary renal neoplasm with reverse polarity may be a novel renal cell tumor entity with low malignant potential

AIMS

This study retrospectively investigated the morphological, immunohistochemical and molecular genetic features of papillary renal neoplasm with reverse polarity (PRNRP), a recently described renal tumor.

METHODS AND RESULTS

Eleven cases of PRNRP were collected, and 16 cases of type I and 9 cases of type II papillary renal cell carcinoma were included as a control series. Pathological features were evaluated based on HE staining and immunohistochemistry. KRAS exon 2 and BRAF V600E mutations were detected by Real-time PCR and Sanger sequencing. Fluorescence in situ hybridization was conducted for identification of chromosomal abnormalities. Hemosiderin deposition was found in a small amount of tumor cells in 6 cases. Multifocal or patchy necrosis (5/11), small focal invasion of the pseudocapsules or renal parenchyma (6/11), and breakthrough of renal capsule with nerve invasion (1/11) were revealed, inconsistent with the previous view that the tumor lacks necrosis and intercellular hemosiderin. Immunohistochemical staining (diffusely positive for CK7 and GATA3, negative for CD117 and vimentin, and negative to weakly positive for P504S) and high frequency of KRAS mutations in exon 2 (9/10) supported the identification and inclusion of our cases. Chromosome 7 trisomy (1/7), chromosome 17 trisomy (0/7) and chromosome Y deletion (0/5 male patients) were seldom detected in this tumor. All patients were alive without metastasis or recurrence at the end of the follow-up.

CONCLUSION

Our findings may highlight the possibility of a low malignant potential of this emerging entity. We suggest that the tumor be classified as a novel renal cell tumor subtype independent of papillary renal cell carcinoma.

Epidemiology and Prevention of Renal Cell Carcinoma

With 400,000 diagnosed and 180,000 deaths in 2020, renal cell carcinoma (RCC) accounts for 2.4% of all cancer diagnoses worldwide. The highest disease burden developed countries, primarily in Europe and North America. Incidence is projected to increase in the future as more countries shift to Western lifestyles. Risk factors for RCC include fixed factors such as gender, age, and hereditary diseases, as well as intervening factors such as smoking, obesity, hypertension, diabetes, diet and alcohol, and occupational exposure. Intervening factors in primary prevention, understanding of congenital risk factors and the establishment of early diagnostic tools are important for RCC. This review will discuss RCC epidemiology, risk factors, and biomarkers involved in reducing incidence and improving survival.

Succinate dehydrogenase B-deficient renal cell carcinoma with a germline variant in a Japanese patient: a case report

Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is a rare renal cancer. A 75-year-old Japanese female presented with gross hematuria. Computed tomography revealed two tumors in the left kidney, which were resected. Immunohistochemistry indicated negative staining for the B subunit of SDH (SDHB) in the resected specimen, leading to a final diagnosis of SDHB-deficient RCC. Genetic testing for SDHB showed a RCC germline variant in exon 6 (NM_003000.3:c.642 G > C) that was previously reported but associated with a novel phenotype (i.e., RCC). Twenty-six years prior, her daughter, who was 25 years old at the time, had undergone radical nephrectomy for a pathologic diagnosis of renal oncocytoma of the right kidney; SDHB immunostaining of her daughter's tumor was also negative retrospectively. We confirmed that her daughter carried the germline variant in SDHB exon 6, similar to the patient. The patient had no evidence of disease progression at 15 months after surgery.

Major heritable renal cell carcinoma syndromes: novel treatment options and future perspectives

PURPOSE OF REVIEW

To provide an overview of diagnosis, genetic abnormalities, clinical signs and treatment options for the major heritable renal cell carcinoma (RCC) syndromes.

RECENT FINDINGS

RCC in major hereditary syndromes are disorders which are typically autosomal dominant. They predispose patients to early onset of RCC and may exhibit other extrarenal manifestations. Early recognition of these diseases allows correct screening at appropriate ages as well as early detection of RCC. Moreover, expedient identification may optimize the management of extra renal manifestations as well as allow for genetic testing and screening of at-risk relatives.

SUMMARY

The risk of RCC in these major heritable syndromes is higher than sporadic disease. They occur at earlier age groups and can be multifocal or bilateral. Tumours are observed until at least 3 cm before any intervention, while nephron sparing surgery is widely considered as the treatment of choice except for hereditary leiomyomatosis with renal cell cancer, of which radical nephrectomy is treatment of choice. Intervention should be timeous as there is a highly reported incidence of early metastasis. Molecular therapies have been used in the setting of patients with metastasis, some of which show favourable outcomes.

Expanding the clinicopathological spectrum of succinate dehydrogenase-deficient renal cell carcinoma with a focus on variant morphologies: a study of 62 new tumors in 59 patients

Most succinate dehydrogenase (SDH)-deficient renal cell carcinomas (RCCs) demonstrate stereotypical morphology characterized by bland eosinophilic cells with frequent intracytoplasmic inclusions. However, variant morphologic features have been increasingly recognized. We therefore sought to investigate the incidence and characteristics of SDH-deficient RCC with variant morphologies. We studied a multi-institutional cohort of 62 new SDH-deficient RCCs from 59 patients. The median age at presentation was 39 years (range 19-80), with a slight male predominance (M:F = 1.6:1). A relevant family history was reported in 9 patients (15%). Multifocal or bilateral tumors were identified radiologically in 5 patients (8%). Typical morphology was present at least focally in 59 tumors (95%). Variant morphologies were seen in 13 (21%) and included high-grade nuclear features and various combinations of papillary, solid, and tubular architecture. Necrosis was present in 13 tumors, 7 of which showed variant morphology. All 62 tumors demonstrated loss of SDHB expression by immunohistochemistry. None showed loss of SDHA expression. Germline SDH mutations were reported in all 18 patients for whom the results of testing were known. Among patients for whom follow-up data was available, metastatic disease was reported in 9 cases, 8 of whom had necrosis and/or variant morphology in their primary tumor. Three patients died of disease. In conclusion, variant morphologies and high-grade nuclear features occur in a subset of SDH-deficient RCCs and are associated with more aggressive behavior. We therefore recommend grading all SDH-deficient RCCs and emphasize the need for a low threshold for performing SDHB immunohistochemistry in any difficult to classify renal tumor, particularly if occurring at a younger age.

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.

The Pathologic and Molecular Genetic Landscape of the Hereditary Renal Cancer Predisposition Syndromes

It is estimated that 5-8% of renal tumors are hereditary in nature with many inherited as autosomal dominant. These tumors carry a unique spectrum of pathologic and molecular alterations, the knowledge of which is expanding in the recent years. Indebted to this knowledge, many advances in treatment of these tumors have been achieved. In this review, we summarize the current understanding of the genetic renal neoplasia syndromes, the clinical and pathologic presentations, their molecular pathogenesis, the advances in therapeutic implications and targeted therapy.

Unclassified Oncocytic Renal Neoplasm with Rib and Liver Metastases: Metastatic Oncocytoma?

Renal tumors with oncocytic or chromophobe-like morphology can be a common source of diagnostic difficulty. In some series, they constitute the largest group of unclassified renal cell carcinomas, a term used for neoplasms that do not fit the current classification of renal tumors. We describe the histological, immunohistochemical, and molecular findings of an eosinophilic renal neoplasm which presented with rib and liver metastases, and provide a review of the literature. The possibility of a renal oncocytoma with metastases was initially considered but excluded on the basis of several morphological and immunohistochemical features. Additionally, the tumor did not correspond with other traditional or newly emerging categories of renal neoplasms. It was therefore regarded as an unclassified oncocytic renal neoplasm which demonstrated evidence of malignant potential due to the presence of multiple metastases.

Overview of the 2022 WHO Classification of Familial Endocrine Tumor Syndromes

This review of the familial tumor syndromes involving the endocrine organs is focused on discussing the main updates on the upcoming fifth edition of the WHO Classification of Endocrine and Neuroendocrine Tumors. This review emphasizes updates on histopathological and molecular genetics aspects of the most important syndromes involving the endocrine organs. We describe the newly defined Familial Cancer Syndromes as MAFA-related, MEN4, and MEN5 as well as the newly reported pathological findings in DICER1 syndrome. We also describe the updates done at the new WHO on the syndromic and non-syndromic familial thyroid diseases. We emphasize the problem of diagnostic criteria, mention the new genes that are possibly involved in this group, and at the same time, touching upon the role of some immunohistochemical studies that could support the diagnosis of some of these conditions. As pathologists play an important role in identifying tumors within a familial cancer syndrome, we highlight the most important clues for raising the suspicious of a syndrome. Finally, we highlight the challenges in defining these entities as well as determining their clinical outcome in comparison with sporadic tumors. Instead of the usual subject review, we present the highlights of the updates on familial cancer syndromes by answering select questions relevant to practicing pathologists.

Germline and sporadic mTOR pathway mutations in low-grade oncocytic tumor of the kidney

Low-grade oncocytic tumor (LOT) of the kidney is a recently described entity with poorly understood pathogenesis. Using next-generation sequencing (NGS) and complementary approaches, we provide insight into its biology. We describe 22 LOT corresponding to 7 patients presenting with a median age of 75 years (range 63-86 years) and male to female ratio 2:5. All 22 tumors demonstrated prototypical microscopic features. Tumors were well-circumscribed and solid. They were composed of sheets of tumor cells in compact nests. Tumor cells had eosinophilic cytoplasm, round to oval nuclei (without nuclear membrane irregularities), focal subtle perinuclear halos, and occasional binucleation. Sharply delineated edematous stromal islands were often observed. Tumor cells were positive for PAX8, negative for CD117, and exhibited diffuse and strong cytokeratin-7 expression. Six patients presented with pT1 tumors. At a median follow-up of 29 months, four patients were alive without recurrence (three patients had died from unrelated causes). All tumors were originally classified as chromophobe renal cell carcinoma, eosinophilic variant (chRCC-eo). While none of the patients presented with known syndromic features, one patient with multiple bilateral LOTs was subsequently found to have a likely pathogenic germline TSC1 mutation. Somatic, likely activating, mutations in MTOR and RHEB were identified in all other evaluable LOTs. As assessed by phospho-S6 and phospho-4E-BP1, mTOR complex 1 (mTORC1) was activated across all cases but to different extent. MTOR mutant LOT exhibited lower levels of mTORC1 activation, possibly related to mTORC1 dimerization and the preservation of a wild-type MTOR copy (retained chromosome 1). Supporting its distinction from related entities, gene expression analyses showed that LOT clustered separately from classic chRCC, chRCC-eo, and RO. In summary, converging mTORC1 pathway mutations, mTORC1 complex activation, and a distinctive gene expression signature along with characteristic phenotypic features support LOT designation as a distinct entity with both syndromic and non-syndromic cases associated with an indolent course.