Primary thyroid-like follicular carcinoma of the kidney: report of 6 cases of a histologically distinctive adult renal epithelial neoplasm. Am J Surg Pathol. 2009;33:393-400. [PMID: 19047894 DOI: 10.1097/pas.0b013e31818cb8f5]

Pediatric thyroid-like follicular renal cell carcinoma-a post-neuroblastoma case with comprehensive genomic profiling data

Thyroid-like follicular renal cell carcinoma (TLFRCC), an emerging subtype of renal cell carcinoma, presents diagnostic challenges due to its resemblance to normal thyroid tissue. Here, we report a rare case of TLFRCC in a pediatric patient, a demographic rarely affected by this subtype. Histologically resembling a typical TLFRCC, our case exhibited unique features including post-neuroblastoma development, occurrence in a male teenager, and diffuse MelanA expression, which has not been previously reported in TLFRCC. Comprehensive genomic profiling revealed the EWSR1::PATZ1 fusion, confirming its genetic basis. Due to the advanced tumor stage, the patient received combined immunotherapy, and after a 9-month follow-up, remains tumor-free. Our case broadens the diagnostic spectrum of pediatric renal cell carcinomas, highlighting the importance of comprehensive molecular profiling in rare subtypes such as TLFRCC. Further research is needed to better understand TLFRCC's genetic landscape and optimize therapeutic strategies, especially in pediatric populations with evolving treatment protocols.

A synchronous presentation of thyroid follicular carcinoma-like renal tumor and papillary vesicular thyroid tumors: About an exceptional case and review of the literature

INTRODUCTION

Thyroid follicular renal cell carcinoma is a special type of renal cell carcinoma newly recognized in recent years. The data is not mature due to the rarity of cases. The association of vesicular papillary tumors of the thyroid is exceptional, and this is the first publication describing such an association in the literature.

CASE PRESENTATION

We present the case of a patient who consulted for a goiter. The definitive pathological examination of the specimen of the thyroidectomy showed papillary vesicular thyroid tumors. A month later, she presented with total hematuria; the CT scan revealed a left renal mass; the patient underwent a partial nephrectomy; and the definitive pathological examination of the specimen showed a thyroid follicular carcinoma-like renal tumor.

DISCUSSION

Thyroid-type follicular cell renal cell carcinomas are currently recognized as a distinct entity whose histological appearance is reminiscent of thyroid vesicular lesions. There are currently around 39 cases in the literature, but no concomitant thyroid localization has been observed. This finding cannot be verified in the absence of a systematic histological study of the thyroid gland. Our case invites discussion of other thyroid investigation modalities, in particular the value of thyroid biopsy versus cytopuncture, which is often inconclusive in this type of situation.

CONCLUSION

At present, understanding of TFCLRT is still very limited. Even more so, their association with a thyroid tumor is exceptional in the literature. We need to increase the number of cases and conduct in-depth investigations with longer follow-up periods to better understand the situation.

Atrophic Kidney-Like Lesion-Case Report and Review of the Literature

Atrophic kidney-like lesion (AKLL) is a rare kidney lesion, which was recently suggested by the Genitourinary Pathology Society as a provisional entity. As of now, 16 examples of AKLL have been described in the literature. Here we report a new tumor which shows similar clinicopathologic characteristics with those previously reported in AKLL. Immunohistochemical (IHC) studies in the current lesion identified a biphasic staining pattern consisting of a mixture of WT1+/KRT7-/PAX8- large dilated cysts and WT-/KRT7+/PAX8+ small atrophic cysts. Histomorphologic features of AKLL overlap with several neoplastic and non-neoplastic entities which can lead to mischaracterization. Awareness of the differentiating features is likely important when evaluating these lesions.

A rare case of thyroid-like follicular carcinoma of the kidney in a 75-year-old male: Case report and review of the literature

INTRODUCTION AND SIGNIFICANCE

The presence of thyroid-like follicular carcinoma in the kidney is very rare, There have been few documented cases of this tumor's formation, and there are no specific signs for this tumor's presence and it is often discovered incidentally by chance, and the diagnosis depends mainly on histological examination and the negative results of thyroid marker tests.

CASE PRESENTATION

We describe the case of an adult male who had prostate adenocarcinoma and later suffered from pain in the flank, so radiographic examination showed a mass in the right kidney, which was removed, and the result of histopathologic examination was thyroid-like follicular carcinoma of the kidney.

CLINICAL DISCUSSION

Although this tumor is rare, we need to keep it in mind as a potential diagnosis for renal lesions in our clinical practice.

CONCLUSION

The presence of a low-grade malignancy and metastasis in this tumor is a good sign, and this is what motivates us to obtain more reports to better understand the nature of this tumor formation, which is important for human health.

Kidney Tumors: New and Emerging Kidney Tumor Entities

This review summarizes current knowledge on several novel and emerging renal entities, including eosinophilic solid and cystic renal cell carcinoma (RCC), RCC with fibromyomatous stroma, anaplastic lymphoma kinase-rearranged RCC, low-grade oncocytic renal tumor, eosinophilic vacuolated tumor, thyroidlike follicular RCC, and biphasic hyalinizing psammomatous RCC. Their clinical features, gross and microscopic morphology, immunohistochemistry, and molecular and genetic features are described. The diagnosis of most of them rests on recognizing their morphologic features using immunohistochemistry. Accurate diagnosis of these entitles will further reduce the category of "unclassifiable renal carcinomas/tumors" and will lead to better clinical management and improved patient prognostication.

Are Renal Cell Carcinoma with Fibromyomatous Stroma (RCC-FMS) and Thyroid-like Follicular Carcinoma of the Kidney (TLFCK) Really Independent Variants?

BACKGROUND

Renal cell carcinoma with fibromyomatous stroma (RCC-FMS) is a recent provisional entity already recognised in the 2016 WHO Classification of Cancer of the Urinary Tract and Male Genital Organs 4th Edition as renal cell carcinoma with (angio)leiomyomatous stroma, histologically defined as a tumour characterised by clear cells intertwined in a conspicuous vascular stroma. In the casuistry taken into consideration, another proposed variant, thyroid-like follicular carcinoma of the kidney (TLFCK), endowed with a morphology mimicking thyroid parenchyma, was examined. The aim of this work was to parse the theoretical system, experimental data and diagnostic impact of these new entities proposed in the field of renal neoplasms.

MATERIALS AND METHODS

An analysis of 120 cases of kidney tumours from the Department of Surgical, Medical, Molecular and Critical Area at the University of Pisa was run. Subsequently, all samples were reassessed by two pathologists with expertise in uropathology, whose revaluation provided a histomorphological study combined with subsequent and coherent immunohistochemical analyses of CK7, CD10, CAIX, CK34betaE12, CD117, vimentin, TTF-1 and thyroglobulin. These analyses were performed using the Ventana Benchmark Automated Staining System (Ventana Medical Systems, Tucson, AZ, USA) and Ventana reagents.

RESULTS

On the one hand, the data, thus brought to light, did not show an immunohistochemical profile consistent with that proposed for RCC-FMS. However, it should be emphasised that the morphological background also unearthed a poor specificity for RCC-FMS. This was specifically due to a stromal component which was, in any case, evident, although characterised by a wide range of presentation, in clear cell renal cell carcinoma (ccRCC). This latter is, indeed, the reference background for this theorised variant. On the other hand, a thyroid-like pattern was highlighted in 11 cases, more specifically in 10 ccRCCs and in one oncocytoma, presenting itself as a type of neoplastic appearance rather than as the peculiar morphological pattern of a standalone cancer.

CONCLUSIONS

In the light of these results, RCC-FMS and TLFCK appear to be more appropriately variants of already categorised neoplastic entities rather than new independent neoplasias.

Kidney Tumors: New and Emerging Kidney Tumor Entities

This review summarizes current knowledge on several novel and emerging renal entities, including eosinophilic solid and cystic renal cell carcinoma (RCC), RCC with fibromyomatous stroma, anaplastic lymphoma kinase-rearranged RCC, low-grade oncocytic renal tumor, eosinophilic vacuolated tumor, thyroidlike follicular RCC, and biphasic hyalinizing psammomatous RCC. Their clinical features, gross and microscopic morphology, immunohistochemistry, and molecular and genetic features are described. The diagnosis of most of them rests on recognizing their morphologic features using immunohistochemistry. Accurate diagnosis of these entitles will further reduce the category of "unclassifiable renal carcinomas/tumors" and will lead to better clinical management and improved patient prognostication.

Metastatic Thyroid Carcinoma to the Kidneys Presenting Initially as Bilateral Renal Masses: A Rare Case Report and Literature Review

Thyroid cancers exist in multiple forms. Papillary and follicular carcinomas of the thyroid are often referred to as well-differentiated thyroid cancers. Well-differentiated thyroid cancers rarely present as a distant metastatic cancer on initial diagnosis. Papillary thyroid cancer tends to have a good prognosis; however, if distant metastasis of PTC is present, there is usually a poor clinical outcome with a less favorable prognosis. In this study, we report a 90-year-old female who presented with right-sided abdominal discomfort. A renal ultrasound revealed bilateral upper pole renal masses. A percutaneous biopsy was ordered, and the microscopic examination revealed bilateral renal metastasis with a follicular variant of papillary thyroid carcinoma. The patient underwent thyroidectomy and sustained radiation therapy for her bilateral renal metastases. She died 6 years after her initial diagnosis, due to sepsis. This is the second study in literature to report bilateral renal metastasis of follicular variant of papillary thyroid cancer.

The 2022 World Health Organization Classification of Tumours of the Urinary System and Male Genital Organs-Part A: Renal, Penile, and Testicular Tumours

The fifth edition of the World Health Organization (WHO) classification of urogenital tumours (WHO "Blue Book"), published in 2022, contains significant revisions. This review summarises the most relevant changes for renal, penile, and testicular tumours. In keeping with other volumes in the fifth edition series, the WHO classification of urogenital tumours follows a hierarchical classification and lists tumours by site, category, family, and type. The section "essential and desirable diagnostic criteria" included in the WHO fifth edition represents morphologic diagnostic criteria, combined with immunohistochemistry and relevant molecular tests. The global introduction of massive parallel sequencing will result in a diagnostic shift from morphology to molecular analyses. Therefore, a molecular-driven renal tumour classification has been introduced, taking recent discoveries in renal tumour genomics into account. Such novel molecularly defined epithelial renal tumours include SMARCB1-deficient medullary renal cell carcinoma (RCC), TFEB-altered RCC, Alk-rearranged RCC, and ELOC-mutated RCC. Eosinophilic solid and cystic RCC is a novel morphologically defined RCC entity. The diverse morphologic patterns of penile squamous cell carcinomas are grouped as human papillomavirus (HPV) associated and HPV independent, and there is an attempt to simplify the morphologic classification. A new chapter with tumours of the scrotum has been introduced. The main nomenclature of testicular tumours is retained, including the use of the term "germ cell neoplasia in situ" (GCNIS) for the preneoplastic lesion of most germ cell tumours and division from those not derived from GCNIS. Nomenclature changes include replacement of the term "primitive neuroectodermal tumour" by "embryonic neuroectodermal tumour" to separate these tumours clearly from Ewing sarcoma. The term "carcinoid" has been changed to "neuroendocrine tumour", with most examples in the testis now classified as "prepubertal type testicular neuroendocrine tumour".

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.

The 2022 revision of World Health Organization classification of tumors of the urinary system and male genital organs: advances and challenges

The fifth edition of the World Health Organization (WHO) classification of urinary and male genital organ tumors has been recently published in 2022. The application of molecular profiling has made a substantial impact on classification of urologic tumors. The new WHO classification introduces a group of molecularly well-defined renal tumor subtypes. The significant changes include addition of a category of "other oncocytic tumors" with oncocytoma/chromophobe renal cell carcinoma (chRCC)-like features, elimination of the subcategorization of type1/2 papillary RCC and inclusion of eosinophilic solid and cystic RCC as an independent tumor entity. The WHO/ISUP grading now has been recommended for all RCCs. Major nomenclature changes include replacement of histologic 'variants' by 'subtypes', 'clear cell papillary renal cell carcinoma' to 'clear cell renal cell tumor','TCEB1-mutated RCC' to 'ELOC-mutated RCC', 'hereditary leiomyomatosis and renal cell carcinoma' to 'fumarate hydratase-deficient RCC', 'RCC-Unclassified' to 'RCC-NOS', 'primitive neuroectodermal tumor' to 'embryonic neuroectodermal tumor', 'testicular carcinoid' to 'testicular neuroendocrine tumor', and 'basal cell carcinoma of the prostate' to 'adenoid-cystic (basal-cell) carcinoma of the prostate'. Metastatic, hematolymphoid, mesenchymal, melanocytic, soft tissue and neuroendocrine tumors are collectively discussed in separate chapters. It has been suggested that the morphological classification of urothelial cancer be replaced with a new molecular taxonomic classification system.

Secondary Tumors of the Kidney: A Comprehensive Clinicopathologic Analysis

Metastases to the kidney are rare and were historically described in autopsy series, and the incidence ranged between 2.36% and 12.6%. However, in the contemporary literature with the improvements in imaging modalities (computed tomography scan and magnetic resonance imaging) and other health care screening services, metastatic tumors to the kidney are being diagnosed more frequently in surgical specimens. The utility of needle core biopsies in the primary evaluation of renal masses has also increased the number of sampled metastases, and as a result, only limited histologic material is available for evaluation in some cases and may potentially lead to diagnostic pitfalls. In the last decade, a few large clinical series have been published. In these series, the majority of metastatic tumors to the kidney are carcinomas, with the lung being the most common primary site. A significant number of the various tumor types with metastasis to the kidney are also associated with widespread metastases to other organs, and the renal metastasis may present several years after diagnosis of the primary tumor. The majority of secondary tumors of the kidney are asymptomatic, incidentally discovered, and solitary. There should be a high index of suspicion of metastasis to the kidney in patients with an associated enlarging renal lesion with minimal to no enhancement on imaging and tumor progression of a known high-grade nonrenal malignancy. Secondary tumors of the kidney can be accurately diagnosed by correlating histopathologic features with clinical and radiographic findings and the judicious use of ancillary studies.

Thyroid follicular renal cell carcinoma excluding thyroid metastases: A case report

BACKGROUND

Thyroid follicular renal cell carcinoma is a special type of renal cell carcinoma newly recognized in recent years. It has attracted attention because of its unique histology, immunophenotype, and clinical characteristics. It has a very low incidence, and the number of case reports available for review is limited. Moreover, a thyroid mass with type of tumour is rare.

CASE SUMMARY

We report a case of a renal mass with a bilateral thyroid mass that was accidentally discovered in a 60-year-old man during physical examination. B-mode ultrasound showed a hypoechoic mass in the middle and lower parenchyma of the right kidney, and computed tomography showed an iso-density shadow tumour in the right kidney. Contrast agents had a significant continuous enhancement effect on the tumour, and the enhancement was not uniform. After partial nephrectomy, pathological analysis was performed to rule out the possibility that the renal tumour was caused by thyroid tumour metastasis. Needle biopsy of the thyroid tumour confirmed that the renal cell carcinoma was not related to the thyroid tumour. The patient was alive at the last postoperative follow-up.

CONCLUSION

This is the third published case in which thyroid tumour biopsy was performed to confirm that thyroid follicular renal cell carcinoma is not thyroid related.

[Thyroid-like follicular carcinoma of the kidney]

Thyroid-like follicular carcinoma of the kidney (TLFCK) is an extremely rare histological variant of renal cell carcinoma, not yet included in the WHO list of tumors. This tumor has a characteristic morphological structure strikingly resembling follicular carcinoma of the thyroid gland, but differing from itby the immunophenotype of tumor cells. TLFCK is characterized by an indolent clinical course, rarely metastases, and even the presence of metastases does not lead to a worsening of the prognosis for the patient. Described a case of TLFCK diagnosed in a 38-year-old patient, observed clinically for 8 years, without metastases during this time, and removed by focal kidney resection. The paper presents the macroscopic and microscopic characteristics of the tumor, immunohistochemical profile, and discusses the issues of differential diagnosis.

Atrophic Kidney Like Lesion: A Provisional Entity With Brief Review of Literature

Atrophic kidney-like lesion (AKLL) is a provisional renal entity with distinct morphological and immunohistochemical features. It characteristically resembles thyroid-like follicular renal cell carcinoma (RCC) of kidney, an emerging renal entity. Very few patients of AKLL have been reported in the literature. We are hereby describing the clinicopathological features of AKLL in a 38-year-old man. The patient was incidentally found to have a renal mass and underwent radical nephrectomy. The morphological and immunohistochemical findings revealed features of AKLL. The patient on 24 months' post-operative period follow-up is alive without recurrence or metastasis.

[Rare kidney tumor - thyroid-like follicular carcinoma]

The literature review provides an analysis of a rare malignant tumor of the kidney: thyroid-like follicular carcinoma of the kidney (TLFCK). In morphology, this tumor is extremely similar to thyroid follicular carcinoma, but the immunophenotype of tumor cells is different. TLFCK has an indolent clinical course, rarely metastasizes, and even the development of metastases does not mean an unfavorable prognosis for the patient. The literature review presents the features of the clinical course of the disease, macroscopic, microscopic, immunohistochemical characteristics of the tumor and typical cytogenetic breakdowns. Particular attention is paid to the issues of differential diagnosis of the tumor with other pathological processes that may microscopically resemble TLFCK.

Thyroid-like follicular renal cell carcinoma with sarcomatoid differentiation and aggressive clinical course: a case report confirming EWSR1::PATZ1 fusion

Thyroid-like follicular renal cell carcinoma (TFRCC) is rare, with <50 cases reported in the litterature. Recently, Al-Obaidy et al. described recurrent EWSR1::PATZ1 fusions in TFRCC, supporting its classification as an independent entity¹ . We report herein a diagnostically challenging case of TFRCC with sarcomatoid differentiation, aggressive clinical course and presence of an EWSR1::PATZ1 fusion.

EWSR1-PATZ1 fusion renal cell carcinoma: a recurrent gene fusion characterizing thyroid-like follicular renal cell carcinoma

Thyroid-like follicular renal cell carcinoma is an uncommon kidney tumor with no distinct molecular alteration described to date. This cohort of eight women with mean and median ages of 45 and 46 years, respectively (range 19-65 years), had unencapsulated, well-circumscribed tumors composed of tightly packed anastomosing follicle-like cysts filled with eosinophilic colloid-like material and lined by cuboidal cells with high nuclear to cytoplasmic ratios, oval to elongated nuclei with perpendicular arrangement toward the lumens, and prominent nuclear overlapping. The stroma between these was minimal with the exception of two tumors. Calcifications and necrosis were absent. Immunohistochemically, the tumors were positive for KRT19 (7/7), PAX8 (5/5), cyclin D1 (6/6), KRT7 (5/7), and AMACR (1/5; focal, weak), and were negative for WT1, TTF1 (transcription termination factor-1), and thyroglobulin. In three of three tumors tested molecularly, EWSR1-PATZ1 fusion was identified by RNA sequencing and confirmed by RT-PCR and Sanger sequencing. Over a follow-up period of 1-7 years, no evidence of recurrence or metastasis has been detected. The EWSR1-PATZ1 fusion has been recognized as a recurrent alteration in a subset of round to spindle cell sarcomas with EWSR1-non-ETS fusions (EWSR1-PATZ1 sarcoma) and in several central nervous system tumors. The finding of an EWSR1-PATZ1 fusion in all three of the thyroid-like follicular renal cell carcinomas for which sufficient tissue was available for genomic profiling provides the first distinct molecular abnormality in thyroid-like follicular renal cell carcinomas, supporting its designation as a distinct diagnostic entity.

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

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

Thyroid-Like Cholangiocarcinoma: Histopathological, Immunohistochemical, In-Situ Hybridization and Molecular Studies on an Uncommon Emerging Entity

Thyroid-like cholangiocarcinoma is a very uncommon variant of peripheral-type cholangiocarcinoma. To date, only 4 prior cases have been reported. The molecular features of this tumor have not been described. We report a case of a 60-year-old woman with a tumor that evolved over a period of 10 years. A left hepatectomy specimen showed an 11 cm tumor that on histology exhibited areas reminiscent of a thyroid tumor with follicular and insular features which were positive on immunohistochemistry for cytokeratin 7 and in-situ hybridization for albumin. A detailed molecular analysis failed to show mutations common to cholangiocarcinomas but revealed frameshift mutations in 2 chromatin-remodeling genes, CREBBP and KMNT2A. This case confirms that thyroid-like cholangiocarcinoma is a histologic variant of this tumor that is associated with relatively low growth. As most cholangiocarcinomas, it is diffusely positive for cytokeratin 7 and albumin by in-situ hybridization. Given its rarity, the molecular alterations in this specific histologic subtype remain to be fully elucidated.

Case Report: Bilateral Renal Cell Carcinoma With Different Histological and Morphological Features, Clear Cell and Cystic Thyroid-Like Follicular Subtype

Thyroid-like follicular renal cell carcinoma is a rare subtype of renal cell carcinoma that has only been recently recognized, as most cases involve a solid tumor in one kidney. In this study, we report a rare case of bilateral renal cell carcinoma wherein the tumor in the left kidney was diagnosed as clear cell carcinoma, while the tumor in right kidney as thyroid-like follicular renal cell carcinoma. The difference between this case and the ones described in previous reports is that thyroid-like follicular renal cell carcinoma showed cystic changes on imaging. This suggests that when renal cystic lesions are encountered, we should consider the possibility of such rare tumors.

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.

A Case of Low-Grade Oncocytic Tumor/Chromophobe Renal Cell Carcinoma (Oncocytic Variant) of the Kidney

The oncocytic variant of chromophobe renal cell carcinoma (oChRCC) and low-grade oncocytic tumor (LOT) is introduced as new renal disease entity. Both of these tumors are low-grade malignancies consisting of cells with eosinophilic cytoplasm. Distinguishing between eosinophilic variant of chromophobe renal cell carcinoma (eCRCC) and oncocytoma is often a diagnostic challenge in routine surgical pathology. However, oChRCC and LOT might be independent disease entities that might not fit completely into any of these categories. Histologically, these tumors have greater morphological similarity with oncocytoma than with ChRCC. However, immunohistochemically, they exhibit diffuse and dense positivity for CK7 and are negative for CD117. In the present case, we initially had difficulty distinguishing among oncocytoma, eCRCC, and type 2 papillary renal cell carcinoma (2-pRCC). However, after learning about new disease entities such as oChRCC and LOT, we were able to diagnose this tumor.

Characterization of a distinct low-grade oncocytic renal tumor (CD117-negative and cytokeratin 7-positive) based on a tertiary oncology center experience: the new evidence from China

To examine the clinicopathologic and immunohistochemical features of a group of newly defined low-grade oncocytic renal tumors (LOT) that have the "CD117 negative/cytokeratin (CK)7 positive" immunoprofile. We have queried our hospital database and found 4456 consecutive renal tumors between 2016 and 2019. Among these renal tumors, eight (8) cases meet the morphologic and immunohistochemical characterization for low-grade oncocytic renal tumor (LOT). The eight (8) patients' mean age is 56.6 years (range 39-70 years old), and the male to female ratio is 1:1. Macroscopically, these LOTs generally present with tan-brown and solid cut surfaces and demonstrate similar solid, compact nested growth pattern microscopically. Tumor cells exhibit oncocytic cytoplasm and uniformly rounded to oval nuclei. There are areas of edematous stroma containing dispersed single or small clustered tumor cells. All tumors are negative for CD117 and positive for CK7. Uniform reactivity is also found for BerEP4, cyclin D1, and SDHB. Besides, CD10, vimentin, and AMACR are either negative or only focally positive. All of the tumors are negative for CA9 and TFE. The Ki-67 index is less than 5% in the seven (7) internal cases. Seven (7) of the eight (8) patients who are available for follow-up are alive and without disease recurrence (mean follow-up period of 21.6 months, ranging from 6 to 43 months). We described a group of low-grade oncocytic renal tumors identified retrospectively in a large tertiary cancer center, which was probably the first report originated from China or even Asia in the English literature so far. These tumors demonstrated eosinophilic cytoplasm and low-grade appearing nuclei with a "CD117 negative/CK7 positive" immunoprofile. The incidence rate was about 3.7% of the oncocytic renal tumors and 0.18% of all the renal tumors that were received in our lab during the four-year period. It is necessary to separate this group of tumors by its characteristic morphologic and immunophenotypic features.

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.

High WHO/ISUP Grade and Unfavorable Architecture, Rather Than Typing of Papillary Renal Cell Carcinoma, May Be Associated With Worse Prognosis

Conflicting data have been published on the prognostic significance of histologic parameters in papillary renal cell carcinoma (PRCC). We conducted a comprehensive evaluation of clinical and histologic parameters in PRCC in nephrectomies and their impact on prognosis, with an emphasis on World Health Organization (WHO)/International Society of Urological Pathology (ISUP) grade, tumor architecture (solid, micropapillary, and hobnail), and PRCC type. A total of 185 PRCC cases were evaluated, 117 (63.2%) type 1, 45 (24.3%) type 2, and 11 (5.9%) mixed type 1 and type 2. Using WHO/ISUP grading criteria, PRCCs were graded as follows: 6 (3.2%) grade 1; 116 (62.7%) grade 2; 61 (33.0%) grade 3; and 2 (1.1%) grade 4. The solid architecture was present in 3 cases (1.6%) and comprised 10%, 10%, and 30% of the tumor area. Micropapillary architecture was present in 10 cases (5.4%), ranging from 5% to 30% of the tumor (mean=11%; median=10%). Hobnail architecture was seen in 9 cases (4.9%), with mean percentage of 23% (median=15%; range: 5% to 50%) involvement of tumor area. Parameters associated with worse disease-free survival (DFS) and overall survival (OS) in the univariate analysis included WHO/ISUP grade, pathologic stage, tumor size, and solid, micropapillary, or hobnail architecture (P<0.05). The pathologic stage and WHO/ISUP grade were significantly associated with both DFS and OS in stepwise multivariate Cox regression analysis (P<0.05). In addition, micropapillary architecture and type 1 histology were linked with an adverse impact on OS (P<0.05). We found no difference in DFS (P=0.8237) and OS (P=0.8222) for type 1 versus type 2 PRCC in our patient cohort. In addition, we performed a meta-analysis with data from studies with reported hazard ratios (HRs) on PRCC type in relation to DFS and OS. We identified 5 studies that reported DFS and found no significant effect for type 2 PRCC (P=0.30; HR=1.43; 95% confidence interval: 0.73-2.80). We identified 7 studies that reported OS and found no significant association between type 2 PRCC and worse OS (P=0.41; HR: 1.21; 95% confidence interval: 0.77-1.91). Our findings suggest that high WHO/ISUP grade and unfavorable architecture (solid, micropapillary, or hobnail), rather than typing of PRCC, are associated with worse outcomes.

Thyroid-Like Follicular Carcinoma of the Kidney With Low-Grade Sarcomatoid Component: A Hitherto Undescribed Case

Thyroid-like follicular carcinoma of the kidney (TLFCK) is a rare subtype of renal cell carcinoma, which closely resembles follicular neoplasms of the thyroid and has a distinctive indolent clinical behavior. Until now, a single case of TLFCK with extensive sarcomatoid differentiation has been documented with aggressive clinical course. We present an unusual case of sarcomatoid TLFCK with a low-grade spindle cell component in a 34-year-old male patient, with an indolent course following radical nephrectomy and regional node dissection.

Thyroid-Like Follicular Carcinoma of the Kidney With Oncocytic Cells: A Case Report and Review of Metastatic and Non-metastatic Tumors

Thyroid-like follicular carcinoma of kidney (TLFCK) is a morphological subtype of renal cell carcinoma, which is included as an emerging/provisional entity in the classification of renal tumors, with only about 40 cases reported in literature. It has a distinct histological appearance and immunohistochemical profile as compared with other renal cell cancers. However, these tumors, while appearing distinctive, have not been characterized fully either morphologically or by ancillary techniques. The reported cases show variable demographical and clinical features. Most are indolent, while some present with metastasis. The histological, immunohistochemical, and ultrastructural features of a case of TLFCK with clusters of oncocytic cells and pseudosarcomatous stroma are presented. Follow-up of 5 years was uneventful. A review of literature to analyze features in metastatic as compared with non-metastatic TLFCK is discussed. We report a patient of TLFCK and compare the clinicopathological features of metastatic and non-metastatic tumors.

Pathologic Doppelgänger: Thyroid-like intrahepatic cholangiocarcinoma with synchronous primary thyroid carcinoma in a young woman

Intrahepatic cholangiocarcinoma (ICC) accounts for 8-10% of all malignant liver tumors. Preponderance for elderly males and occurrence of varied morphological patterns in ICC is well known. Recent reports have described a newly recognized variant of thyroid-like cholangiocarcinoma. Herein, we present a hitherto unreported synchronous occurrence of an intrahepatic thyroid-like cholangiocarcinoma and a separate thyroid carcinoma in a 23-year-old post-partum woman. Both tumors displayed striking resemblance to follicular variant of papillary thyroid carcinoma (FVPTC) however exhibited disparate immunohistochemical profiles: the intrahepatic tumor was positive for CK7 and CK19, and negative for TTF-1, PAX-8 and thyroglobulin whereas, the thyroid tumor was positive for TTF-1, thyroglobulin and PAX-8. Young age, female proclivity, large mass at presentation and unique histology in thyroid-like ICC hint towards a distinctive subset of ICC. Awareness and recognition of this rare entity is essential, not only for accurate diagnosis, but also for gathering information on its biology and clinical behavior. Synchronous occurrence with a FVPTC is a challenging scenario that can simulate metastatic disease and mislead subsequent patient management. Whether morphologic similarity points to an underlying linkage between the two different tumors needs exploration.

[The morphological characteristics and immunophenotype of renal cell carcinomas with eosinophilic cytoplasm]

Eosinophilic cellular renal cell carcinomas embrace a wide range of histological types described in the 2016 WHO International Classification of Kidney Tumors. A variety of histological manifestations associated with the features of tumor morphogenesis in this group poses difficulties in differential diagnosis.

AIM

to investigate the morphological and immunophenotypic features of rare types of renal cell carcinomas with eosinophilic cytoplasm.

SUBJECTS AND METHODS

An investigation was conducted using a surgical material from 294 patients with a kidney tumor. An immunohistochemical (IHC) study was performed on paraffin sections according to the standard protocol using a wide panel of antibodies.

RESULTS

Based on a morphological analysis and IHC study, the tumors were divided into 3 groups: 1) 127 (43%) oncocytic tumors that expressed classical IHC markers for oncocytoma and chromophobe renal cell carcinoma; 2) 50 (17%) oncocytic tumors that did not correspond to the immunophenotypes of oncocytoma and chromophobe renal cell carcinoma; and 3) 117 (40%) eosinophilic cellular nononcocytic renal tumors.

CONCLUSION

With the advent of the current differential diagnostic criteria, the classification of renal cell carcinomas continues to expand. To date, a hybrid oncocytic/chromophobic tumor, eosinophilic solid and cystic renal cell carcinoma, and follicular kidney cancer should be regarded as new nosological entities.

[Characterization of different renal cell carcinoma entities]

BACKGROUND

In recent years, the characterization of different renal cell carcinoma entities has significantly improved, in particular due to molecular typing.

OBJECTIVES

Classical, accepted and emerging renal cell carcinoma entities are described.

MATERIALS AND METHODS

A literature search was performed, followed by evaluation and description of the literature focusing on different renal cell carcinoma entities.

RESULTS

Classical renal cell carcinoma entities such as clear cell carcinoma, papillary renal cell carcinoma and chromophobe renal cell carcinoma have been expanded in particular by molecular techniques to include, for example, translocation carcinoma or carcinoma with mutations in genes of the mitochondrial energy metabolism. Some rare entities have been accepted by the World Health Organization (WHO) classification, while some are considered as emerging entities.

CONCLUSIONS

A range of newly accepted and emerging renal cell carcinoma entities have been introduced in the 2016 WHO classification. A precise and correct diagnosis is of major importance regarding the prognostic assessment, potential new therapeutic strategies and possible hereditary associations.

Five decades of urologic pathology: the accelerating expansion of knowledge in renal cell neoplasia

Those who are knowledgeable in cosmology inform us that the expansion of the universe is such that the velocity at which a distant galaxy is receding from the observer is continually increasing with time. We humbly paraphrase that as "The bigger the universe gets, the faster it gets bigger." This is an interesting analogy for the expansion of knowledge in the field of renal tumor pathology over the past 30 to 50 years. It is clear that a multitude of dedicated investigators have devoted incalculable amounts of time and effort to the pursuit of knowledge about renal epithelial neoplasms. As a consequence of the contributions of numerous investigators over many decades, the most recent World Health Organization classification of renal neoplasms includes about 50 well defined and distinctive renal tumors, as well as various miscellaneous and metastatic tumors. In addition, a number of emerging or provisional new entities are under active investigation and may be included in future classifications. In this review, we will focus on a number of these tumors, tracing as accurately as we can the origins of their discovery, relating relevant additions to the overall knowledge base surrounding them, and in some instances addressing changes in nomenclature.

Thyroid-like follicular carcinoma of the kidney presenting on a 10 year-old prepubertal girl

The very rare thyroid-like carcinoma of the kidney (TLCK) is microscopically similar to thyroid follicular cell carcinoma (TFCC). Differential diagnosis with secondary thyroid tumors depends on non-reactivity to immunohistochemical (IHC) markers for TFCC (thyroglobulin - TG and TTF1). We herein describe the fourth Pediatric case in literature and extensively review the subject. Only 29 cases were published to the moment. Most cases were asymptomatic and incidentally detected. Most tumors are hyperechoic and hyperdense with low grade heterogenous enhancement on CT and MRI. Most patients were treated with radical nephrectomy, but partial nephrectomy was used in some cases, apparently with the same results. Metastases are uncommon and apparently do not change prognosis, but follow-ups are limited. Up to the moment, TLCK presents as a low grade malignancy that may be treated exclusively with surgery and frequently with partial kidney renal preservation. A preoperative percutaneous biopsy is a common procedure to investigate atypical tumors in childhood and adult tumors. To recognize the possibility of TLCK is fundamental to avoid unnecessary thyroidectomies in those patients, supposing a primary thyroid tumor.

"Atrophic Kidney"-like Lesion: Clinicopathologic Series of 8 Cases Supporting a Benign Entity Distinct From Thyroid-like Follicular Carcinoma

Renal mass lesions with a follicular architecture resembling atrophic kidney have been described, but their distinction from thyroid-like follicular carcinoma of the kidney remains controversial. We collected 8 cases of this purported "atrophic kidney"-like lesion to fully describe their clinical and histologic spectrum, their possible etiology, and to discuss their distinction from other renal neoplasms. Eight total cases were identified with patient ages ranging from 9 to 48 years (mean: 29 y; median: 28.5 y). Four patients were female and 4 were male. The tumors were unifocal and size ranged from 1.6 to 4.9 cm (mean: 3.4 cm; median: 3.4 cm). All 8 tumors had a remarkably similar histology. Each was enveloped by a smooth muscle rich capsule and had an overall low power "follicular" architecture. The luminal spaces of the "follicles" (or cysts) contained eosinophilic secretions and the lining epithelium was often flattened and atrophic, but some had more rounded cells with a distinctive hobnail arrangement. Many cysts contained discohesive round cells floating within the eosinophilic material, and some contained small intraluminal tufts with features of markedly atrophic glomeruli. Periodic acid-Schiff stains highlighted basement membrane material extending into these glomerular-like tufts, and some contained small distinct capillaries surrounded by endothelial cells, interspersed mesangial-like cells, and rare surrounding podocyte-like cells, providing additional evidence for glomerulocystic structures. Scattered calcifications were present within cysts (or within cyst walls) in varying numbers and were characterized by 2 types: psammoma body-like or more amorphous deposits. The tissue between cystic glomeruli contained predominantly small atrophic tubular structures, but collagenized stroma and smaller collapsed glomeruli were also present. The 2 tumors from the oldest 2 patients (48 and 39 y) had a more striking degree of stromal hyalinization. Immunohistochemically, the cyst lining cells had a predominant WT-positive/PAX-8 negative/CK7-negative phenotype, while tubules were typically WT-1 negative/PAX-8 positive/CK7-positive. Upon comparison to a control group of 10 kidneys containing incidental non-mass-forming glomerulocystic change, the morphologic features and immunophenotype were identical. To date, no patient has had any recurrence or aggressive clinical behavior based on follow status in 7 of 8 cases (follow-up range: 9 to 168 mo; median: 24 mo; mean: 40 mo). In summary, we describe the clinicopathologic features of 8 unique, benign "atrophic kidney"-like lesions that may simply represent a non-neoplastic form of organizing tubular atrophy and glomerulocystic change, and emphasize their distinction from thyroid-like follicular carcinoma of the kidney.

Eosinophilic Kidney Tumors: Old and New

Context.—

Eosinophilic cytoplasm is the most common finding of difficult-to-classify kidney tumors. Morphology, cytogenetics, and immunohistochemical stains are discriminatory. This review compares well-recognized tumors such as granular clear cell carcinoma, papillary variants, chromophobe renal cell carcinoma, and oncocytoma and introduces newly described entities of hybrid oncocytic tumors, carcinomas defined by translocations, and carcinomas with deficiencies in the tricarboxylic acid cycle. The focus is on immunostaining, clinical correlations, and differential diagnoses. Representative examples of some entities are presented with elaboration on their workup.

Objective.—

To provide a review of the differential diagnoses for renal neoplasms with eosinophilic cytoplasm and elaborate on methods that may assist with correct identification.

Data Sources.—

Review of current literature on kidney tumors with eosinophilic cytoplasm, as well as the authors' personal experience.

Conclusions.—

Eosinophilic cytoplasm is a feature shared by many kidney tumors. Understanding the morphologic differences and the role of ancillary studies is key when encountering such a tumor.

Thyroid-Like Follicular Renal Cell Carcinoma Arising Within Benign Mixed Epithelial and Stromal Tumor

Thyroid-like follicular renal cell carcinoma (TLF-RCC) is an extremely rare tumor with less than 40 published reports. These tumors are morphologically distinct with striking resemblance to thyroid follicular tumors, but immunohistochemically different due to lack of thyroglobulin and thyroid transcription factor 1 expression. TLF-RCCs arise in younger patients (mean age = 41 years) with female predominance and in all reported cases were solitary tumors without coexisting epithelial or mesenchymal kidney neoplasms. In this article, we report a case of a 42-year-old woman who presented with an incidental 4-cm solid and cystic left renal mass of the upper pole, which was resected. A detailed imaging assessment, pathologic findings, and immunohistochemical studies revealed a partially encapsulated TLF-RCC arising in a background of mixed epithelial and stromal tumor.

Acinar cell carcinoma of the pancreas with thyroid-like follicular features: first description of a new diagnostic challenging subtype

Acinar cell carcinomas (ACCs) of the pancreas are a heterogeneous group of neoplasms showing a wide spectrum of morphological features including acinar, solid, glandular, and trabecular architecture. In addition, uncommon cytological aspects have recently been described and include oncocytic, spindle, clear, and pleomorphic cell types. This wide histological spectrum represents a challenge in the diagnostic task for pathologists. Molecular mechanisms involved in the onset and progression of ACCs are not completely known, but, in general, they differ from those observed in ductal adenocarcinomas or neuroendocrine neoplasms of the pancreas and frequently include alterations in the APC/β-catenin pathway. In the present paper, we describe a new variant of ACC showing thyroid-like follicular features and CTNNB1 mutation. This phenotype needs to be included in the spectrum of morphological presentation of ACC.

Thyroid-Like Follicular Carcinoma of the Kidney With Extensive Sarcomatoid Differentiation: A Case Report and Review of the Literature

Thyroid-like follicular carcinoma of the kidney (TLFCK) is an extremely rare primary renal malignancy that typically has an indolent course and good prognosis. Histologically, this tumor mimics follicular carcinoma of the thyroid; however, typical thyroid markers are negative. There are fewer than 40 cases reported in the literature, and thus, the prognosis and course of disease is not well understood. Sarcomatoid differentiation has never been reported in a case of TLFCK. We present a case of a 48-year-old woman with an aggressive TLFCK with extensive sarcomatoid differentiation and metastatic disease at presentation. We performed targeted next-generation sequencing of both the thyroid-like component and the poorly differentiated sarcomatoid component using our solid tumor panel to evaluate for any disease-associated mutations and to better understand the molecular profile of these tumors.

Emerging entities of renal cell neoplasia

The current classification of renal cell carcinoma (RCC) was formulated at the meeting of the World Health Organization Renal Tumor Panel in 2015, with the results published in the fourth edition of the World Health Organization Classification of Tumours of the Urinary System and Male Genital Organs Bluebook in 2016. At that meeting a number of tumor types were designated as emerging or provisional entities as it was felt that they were insufficiently characterized to merit inclusion as a recognized type of RCC. One tumor type included in this designation was thyroid-like follicular RCC. Since the publication of the 2016 classification this tumor type has been further characterized and in addition to this, detailed studies on three other types of RCC (multifocal oncocytoma-like tumors associated with oncocytosis, eosinophilic solid and cystic RCC and biphasic squamoid alveolar RCC) have been published. It is now apparent that these four tumors are unique morphotypes and genotypes of RCC, and are likely to be included in the next edition of the World Health Organization classification of renal tumors. Multifocal oncocytoma-like tumors associated with oncocytosis is a benign process characterized by the presence of hundreds to thousands of oncocytic tumors in a single kidney. These tumors occur sporadically and are unrelated to the tumors of Birt-Hogg-Dubé syndrome. Eosinophilic solid and cystic RCC is characterized by a solid and cystic architecture with tumor cells consisting of bulky eosinophilic and granular cytoplasm with intracytoplasmic vacuolation. Thyroid-like follicular RCC occurs in younger patients with a female predominance. The tumor bears a striking resemblance to follicular carcinoma of the thyroid with follicles containing intraluminal proteineacous material resembling thyroglobulin. Immunostains for thyroid markers are negative. Finally, biphasic squamoid alveolar RCC consists of aggregates of large cells with pale eosinophilic cytoplasm usually arranged in a glomeruloid/alveolar pattern and surrounded by a border of basophilic cells with scanty cytoplasm. The genotype of the tumor, as well its recorded association with typical papillary RCC, has led to the suggestion that it is related to type 1 papillary RCC.

Early onset renal cell carcinoma in an adolescent girl with germline FLCN exon 5 deletion

Birt-Hogg-Dube (BHD) disease is an autosomal dominant cancer syndrome characterized by benign skin tumors, renal cancer and spontaneous pneumothorax and is caused by mutations in the Folliculin (FLCN) gene. Benign skin tumors and pneumothorax occur in the majority of patients affected by BHD syndrome, but only 30-45% of them develop renal cell carcinoma (RCC) with a median age of diagnosis at 48. The earliest onset of RCC in a BHD patient has been reported at age 20. Here we report a case of a 14 year-old patient with germline FLCN mutation leading to an early-onset bulky RCC that could not be classified strictly according to existing histological types. Germline genetic testing revealed a deletion at FLCN exon 5. The father of the patient was identified as the asymptomatic carrier. We report the youngest patient with BHD-related RCC. This early onset presentation supports genetic testing of at-risk patients and initiation of imaging surveillance for RCC in early adolescence. In addition, future studies are necessary to understand the determinants of reduced penetrance in BHD disease.

Whole-genome and transcriptome profiling of a metastatic thyroid-like follicular renal cell carcinoma

Thyroid-like follicular renal cell carcinoma (TLFRCC) is a rare cancer with few reports of metastatic disease. Little is known regarding genomic characteristics and therapeutic targets. We present the clinical, pathologic, genomic, and transcriptomic analyses of a case of a 27-yr-old male with TLFRCC who presented initially with bone metastases of unknown primary. Genomic DNA from peripheral blood and metastatic tumor samples were sequenced. A transcriptome of 280 million sequence reads was generated from the same tumor sample. Tumor somatic expression profiles were analyzed to detect aberrant expression. Genomic and transcriptomic data sets were integrated to reveal dysregulation in pathways and identify potential therapeutic targets. Integrative genomic analysis with The Cancer Genome Atlas (TCGA) data set revealed the following outliers in gene expression profiles: CDK6 (81st percentile), MYC (99th percentile), AR (100th percentile), PDGFRA and PDGFRB (99th and 100th percentiles, respectively), and MAP2K2 (86th percentile). The patient received first-line sunitinib to target PDGFRA and PDGFRB and had stable disease for >6 mo, followed by nivolumab upon progression. To the authors’ knowledge, this is the first reported case of comprehensive somatic genomic analyses in a patient with metastatic TLFRCC. Somatic analyses provided molecular confirmation of the primary site of cancer and potential therapeutic strategies in a rare disease with little evidence of efficacy on systemic therapy.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Thyroid follicular carcinoma-like renal tumor: A case report and literature review

RATIONALE

Thyroid follicular carcinoma-like renal tumor (TFCLRT) is a rare primary renal epithelial tumor that was first reported in 2006. We report a case diagnosed of TFCLRT by us to observe the pathological feature and analyze comparatively the clinical and pathologic characteristics with all cases of reviewed literatures.

PATIENT CONCERNS

A 54-year-old female patient had the urinary frequency with the symptom of right flank pain with a history of more than half a year of hypertension and received uterine fibroid resection 12 years ago. B-mode ultrasound examination and renal magnetic resonance showed a right renal sinus nodule.

DIAGNOSES

Histopathology revealed thyroid follicle-like structures of different sizes, containing a colloid-like substance, while the periodic acid-Schiff (PAS) and diastase-resistant PAS staining confirmed that it was mucus protein. Immunohistochemical staining showed that it expresses the transcription factor PAX-8 but does not express the thyroid-specific antibodies TG and TTF-1.

INTERVENTIONS

The patient underwent a tumor enucleation of right kidney. No other treatment was conducted after surgery.

OUTCOMES

No metastases to lymph nodes and other organs were found, and 9-months of follow-up did not reveal any tumor progression.

LESSONS

We should differentially diagnose the renal metastasis of thyroid follicular carcinoma or papillary carcinoma. Some related literatures reported that the tumour cells had significant heteromorphism, several of which metastasized to lymph nodes or distal organs. Its biological behavior need to be studied intensively by further expanding the number of cases.

Thyroid-Like Metastases to the Scalp from a Papillary Renal Cell Carcinoma: A Case Report

The skin can host metastatic tumors originating from different organs. We report a case of metastatic renal cell carcinoma to the scalp in a 73-year-old man with features very similar to those of thyroid papillary carcinoma. The histogenesis in relation to its structure is discussed.

Emerging entities in renal cell neoplasia: thyroid-like follicular renal cell carcinoma and multifocal oncocytoma-like tumours associated with oncocytosis

The list of accepted entities of renal cell neoplasia has burgeoned since the turn of the century through recognition of rare tumour types and the discovery of genetic mutations driving renal neoplasia syndromes. This growth has not finished and in this report we present examples of each of these types which were not included in the 2016 World Health Organization classification of renal neoplasia, but are candidates for inclusion in the next edition of the classification. Thyroid-like follicular renal cell carcinoma is a rare tumour type with a distinctive microscopic appearance resembling follicles of the thyroid gland. Thirty-nine cases have been described and the findings have been reasonably consistent. Oncocytoma-like tumours associated with oncocytosis arise as a result of somatic mutations in the mitochondrial genome. The differential diagnosis is mainly with the renal lesions of the Birt-Hogg-Dubé syndrome, which is the result of germline mutations in the folliculin gene. Patients with oncocytoma-like tumours associated with oncocytosis are at great risk of developing renal failure as the proliferating lesions replace the renal parenchyma. Oncocytoma-like tumours have never been found to metastasise.