Thyroid follicular carcinoma-like tumor of kidney: a case report with morphologic, immunohistochemical, and genetic analysis

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.

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.

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".

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.

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.

[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.

Metastatic thyroid carcinoma mimicking as a primary neoplasia of the kidney: A case report

The unfavorable behavior of primary thyroid carcinoma (PTC) has been revealed by the hematogenous distant metastases in ~20-25% of cases with frequent localizations in lungs and bones, but infrequently in kidney. A 69-year-old male patient was admitted to Department of Human Pathology in Adulthood and Childhood 'G. Barresi', University Hospital G. Martino, (Messina, Italy) for an incidentally detected parenchymal mass involving the right kidney. A partial nephrectomy was done; at the post-surgical examination, a large nodular grayish mass was documented. Microscopically, a diffuse proliferation with solid/follicular pattern with some colloid-filled spaces was appreciable. An intense immunopositivity was revealed for thyroglobulin, thyroid transcription factor-1 (TTF-1), paired-box gene 8 (PAX-8) and cytokeratin 7, while CD10 and renal cell carcinoma marker were negative. A diagnosis of the metastatic thyroid follicular carcinoma localized in the kidney was made. At ultrasound examination, a hyperechoic mass extending from the left thyroid lobe to the isthmus, to which TIR4 diagnostic category according to the Italian reporting system for thyroid cytology was attributed. After thyroid surgical procedure, the final diagnosis of primitive differentiated follicular thyroid carcinoma with foci of poorly differentiated component was made.

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).

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

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

Renal Cell Tumors: Molecular Findings Reshaping Clinico-pathological Practice

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

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.

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.

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.

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.

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.

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.

Clinicopathological study on thyroid follicular carcinoma-like renal tumor related to serious hypertension: Case report and review of the literature

RATIONALE

Thyroid carcinoma-like tumor of the kidney (TLFCK) is an extremely rare variant of renal cell carcinoma. Most cases were incidentally found, while we report the first case of TLFCK presented with hypertension.

PATIENT CONCERNS

A 25-year-old woman was admitted to our hospital presenting with hypertension for ∼20 months, without gross hematuria, weight loss, and flank pain.

DIAGNOSES

Imaging studies revealed a right renal mass with multiple calcifications. Histologically, the tumor had striking follicles with dense, colloid-like material resembling thyroid follicular carcinoma while the tumor cells were negative for thyroid markers (thyroglobulin and thyroid transcription factor-1).

INTERVENTIONS

The patient successfully underwent nephron sparing surgery with an uneventful recovery.

OUTCOMES

Hypertension returned to normal without any medication interference. Two years after surgery, the patient is still in good health without recurring disease or related hypertension.

LESSONS

Recognition of the cytomorphological features of TLFCK can avoid misdiagnosis of this renal tumor as a metastatic carcinoma and the objective of surgical management is to remove the tumor and preserve renal function.

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

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

Thyroid-Like Follicular Carcinoma of the Kidney in a Patient with Skull and Meningeal Metastasis: A Unique Case Report and Review of the Literature

Thyroid-like follicular carcinoma of the kidney (TLFCK) is an extremely rare subtype of renal cell carcinoma with close resemblance to the well-differentiated thyroid follicular neoplasms. TLFCK has not been included in the 2004 World Health Organization (WHO) classification due to the limited data available. Only 27 cases have been reported in the literature to date. Herein, we report a unique case of TLFCK that presented as a striking skull and meningeal metastasis 5 years after the initial diagnosis; this is the first case of TLFCK with such a novel metastasis pattern. A 68-year-old woman was found to have a right renal lesion using computed tomography (CT) during her regular clinical follow-up visit for bladder cancer, but she exhibited no obvious clinical symptoms. The CT scan showed a 4.4-cm diameter, slightly lobulated soft tissue mass in the right lower kidney, the pathological findings of which showed a TLFCK. Five years later, the patient had progressed to skull and meningeal metastasis. Both the renal tumor and the metastasis lesion were composed almost entirely of follicles with a dense, colloid-like material that resembled thyroid follicular carcinoma. However, no lesion was found in the thyroid gland. The neoplastic epithelial cells were strongly immunoreactive for cytokeratin 7 (and vimentin but negative for thyroid transcription factor-1 and thyroglobulin. This is the first reported case of TLFCK to consist of widespread metastases to the skull and meninges and provides evidence that this rare variant of renal cell carcinoma has uncertain malignant potential and can be more clinically aggressive than previously believed.

Emerging Entities in Renal Neoplasia

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

Clinical characteristics and pathology of thyroid-like follicular carcinoma of the kidney: Report of 3 cases and a literature review

Thyroid-like follicular carcinoma (TLFC) of the kidney is an extremely rare type of renal tumor, which has not been classified under a known subtype of renal cell carcinoma. It is histologically similar to the primary thyroid follicular carcinoma; however, the characteristics lack thyroid immunohistochemical markers. The aim of the present study was to illustrate the clinical characteristics of 3 new cases along with a review of the literature. The patients were compared with regards to gender, age, location and size of the tumor, imageology, morphology, immunohistochemistry and prognosis. According to the limited data, TLFC occurs mainly in young women and its clinical manifestations have no difference with other renal tumors. Its imageological features resemble a large spectrum of benign and malignant renal and extra-renal conditions, which should be eliminated in the diagnostic process. Confirmed diagnosis depends on the examination of pathology and immunohistochemistry. Surgical ablation is the preferred therapeutic method. Currently, TLFC has a relatively good prognosis; however, this conclusion requires further cases and long-term follow-ups. Improving the understanding of TLFC can help avoid misdiagnosis and prevent inappropriate treatment.

Thyroid-like follicular carcinoma of the kidney: one case report and review of the literature

OBJECTIVES

Thyroid-like follicular carcinoma of the kidney continues to confound the practicing pathologist with its close resemblance to the follicular variant of thyroid carcinoma, as well as other benign and malignant entities. Our goal is to expand the knowledge of this rare renal cell carcinoma subtype, which is morphologically similar to follicular carcinoma of the thyroid but lacks expression of characteristic thyroid immunohistochemical markers such as TTF-1 and thyroglobulin.

METHODS

We evaluated the gross, histologic, immunohistochemical, and fluorescence in situ hybridization (FISH) studies of a new case and performed a comprehensive review of the literature.

RESULTS

The lesion was spongy and well-circumscribed. Microscopically it showed variably sized follicular structures, filled with abundant, deeply eosinophilic, colloid-like material. At the periphery, it displayed areas resembling metanephric adenoma and early stages of nephrogenesis. The tumor cells strongly expressed CK7, PAX-8, PAX-2, vimentin, EMA, and CK19 immunostains. Other markers, such as CD10, RCC, HBME-1, thyroglobulin, and TTF-1, were not immunoreactive. The tumor was negative for trisomy of both 7 and 17 and showed borderline monosomies (losses) of both chromosomes in FISH studies.

CONCLUSIONS

Five years of preoperative observation and lack of recurrence bring further insight into the slow progressive nature of this neoplasm and support a low malignant potential. Proper identification is important to secure adequate treatment and follow-up.

The evolving classification of renal cell neoplasia

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

Diagnostic approach to eosinophilic renal neoplasms

CONTEXT

Eosinophilic renal neoplasms include a spectrum of solid and papillary tumors ranging from indolent benign oncocytoma to highly aggressive malignancies. Recognition of the correct nature of the tumor, especially in biopsy specimens, is paramount for patient management.

OBJECTIVE

To review the diagnostic approach to eosinophilic renal neoplasms with light microscopy and ancillary techniques.

DATA SOURCES

Review of the published literature and personal experience.

CONCLUSIONS

The following tumors are in the differential diagnosis of oncocytic renal cell neoplasm: oncocytoma, chromophobe renal cell carcinoma (RCC), hybrid tumor, tubulocystic carcinoma, papillary RCC, clear cell RCC with predominant eosinophilic cell morphology, follicular thyroid-like RCC, hereditary leiomyomatosis-associated RCC, acquired cystic disease-associated RCC, rhabdoid RCC, microphthalmia transcription factor translocation RCC, epithelioid angiomyolipoma, and unclassified RCC. In low-grade nonpapillary eosinophilic neoplasms, distinction between oncocytoma and low-grade RCC mostly rests on histomorphology; however, cytokeratin 7 immunostain may be helpful. In high-grade nonpapillary lesions, there is more of a role for ancillary techniques, including immunohistochemistry for cytokeratin 7, CA9, CD10, racemase, HMB45, and Melan-A. In papillary eosinophilic neoplasms, it is important to distinguish sporadic type 2 papillary RCC from microphthalmia transcription factor translocation and hereditary leiomyomatosis-associated RCC. Histologic and cytologic features along with immunohistochemistry and fluorescence in situ hybridization tests for TFE3 (Xp11.2) and TFEB [t(6;11)] are reliable confirmatory tests. Eosinophilic epithelial neoplasms with architecture, cytology, and/or immunoprofile not qualifying for either of the established types of RCC should be classified as unclassified eosinophilic RCC and arbitrarily assigned a grade (low or high).

Thyroid-like follicular carcinoma of the kidney: a case report and review of the literature

Thyroid-like follicular carcinoma of the kidney is an extremely rare histological variant of renal cell carcinoma. It was described only recently and is not included in the World Health Organization classification of renal tumors. This tumor characteristically shows similar histology to thyroid follicular carcinoma but lacks typical thyroid markers. Herein, we report a new case of thyroid-like follicular carcinoma of the kidney diagnosed in a partial nephrectomy specimen in a 68-year-old-woman. We present typical histological and immunohistochemical findings, discuss differential diagnosis and provide a review of the literature.

Virtual Slides: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_186

Thyroid-like follicular carcinoma of the kidney in a young patient with history of pediatric acute lymphoblastic leukemia

Thyroid-like follicular carcinoma of the kidney (TLFCK) is a rare histological variant of renal cell carcinoma not currently included in the World Health Organization classification of renal tumors. Only 24 previous cases of TLFCK have been reported to date. We report a case of TLFCK in a 19-year-old woman with history of pediatric acute lymphoblastic leukemia. This patient is the youngest with TLFCK to be reported to date and the first with history of lymphoblastic leukemia. The development of TLFCK in a young patient with history of lymphoblastic leukemia is interesting and suggests that genes involved in leukemogenesis may also be important for TLFCK pathogenesis. Recognition of TLFCK is important to distinguish it from other conditions that show thyroid-like features, as a misdiagnosis can result in adverse patient care.

Recent advances of immunohistochemistry for diagnosis of renal tumors

The recent classification of renal tumors has been proposed according to genetic characteristics as well as morphological difference. In this review, we summarize the immunohistochemical characteristics of each entity of renal tumors. Regarding translocation renal cell carcinoma (RCC), TFE3, TFEB and ALK protein expression is crucial in establishing the diagnosis of Xp11.2 RCC, renal carcinoma with t(6;11)(p21;q12), and renal carcinoma with ALK rearrangement, respectively. In dialysis-related RCC, neoplastic cells of acquired cystic disease-associated RCC are positive for alpha-methylacyl-CoA racemase (AMACR), but negative for cytokeratin (CK) 7, whereas clear cell papillary RCC shows the inverse pattern. The diffuse positivity for carbonic anhydrase 9 (CA9) is diagnostic for clear cell RCC. Co-expression of CK7 and CA9 is characteristic of multilocular cystic RCC. CK7 and AMACR are excellent markers for papillary RCC and mucinous tubular and spindle cell carcinoma. CD82 and epithelial-related antigen (MOC31) may be helpful in the distinction between chromophobe RCC and renal oncocytoma. WT1 and CD57 highlights the diagnosis of metanephric adenoma. The combined panel of PAX2 and PAX8 may be useful in the diagnosis of metastatic RCC.

Thyroid-like follicular carcinoma of the kidney: A report of two cases and literature review

There have only been a few reports of thyroid-like follicular carcinoma of the kidney (TLFCK) to date. In the present study, two patients with TLFCK are reported. Patient 1 was a 65-year-old male exhibiting repeated hematuria and right back pain. No tumors were located in the patient's thyroid or lungs. The physical examination revealed percussion tenderness over the right kidney region was noticed. Enhanced computed tomography (CT) indicated a right renal pelvic carcinoma, for which the patient underwent a radical right nephrectomy. Patient 2 was a 59-year-old male with a mass in the right kidney, located during a health examination and who exhibited no obvious clinical symptoms. The patient was clinically diagnosed with right renal carcinoma, confirmed by an enhanced CT. The patient underwent a radical right nephrectomy. The clinical features, imaging results, pathology, immune phenotypes, treatment and prognosis were analyzed. The associated literature was also reviewed. The cut surface of each tumor showed gray-white material with a central solid area, including scattered gray-brown necrotic and gray hemorrhagic areas and small cystic cavities. Microscopically, the arrangement of the tumor cells mimicked thyroid follicles with red-stained colloid-like material in the lumen. No renal hilar lymph node involvement was noted. The tumor tissue of patient 1 was immunohistochemically positive for vimentin, epithelial membrane antigen (EMA), cytokeratin (CK), CK7, and neuron specific enolase; and negative for CK34BE12, synapsin (Syn), CK20, cluster of differentiation 56 (CD56), CD10, Wilm's tumor-1 (WT-1), CD34, CD57, P53, CD99, thyroid transcription factor-1 (TTF-1), CD15 and thyroglobulin (TG); with a Ki-67 labeling index (LI) of 30%. The tumor tissue of patient 2 was immunohistochemically positive for vimentin, EMA, CK7 and CK20; and negative for CD56, CD10, WT-1, CD34, CD57, P53, CD117, TTF-1, CD15, CD99, TG, chromogranin A and Syn; with a Ki-67 LI of 20%. TLFCK is a rare renal tumor with low malignancy but medium invasiveness. It morphologically resembles thyroid follicular carcinoma but does not express TTF-1 or TG. Radical nephrectomy can achieve good patient outcomes.

Renal cell carcinoma: Evolving and emerging subtypes

Our knowledge of renal cell carcinoma (RCC) is rapidly expanding. For those who diagnose and treat RCC, it is important to understand the new developments. In recent years, many new renal tumors have been described and defined, and our understanding of the biology and clinical correlates of these tumors is changing. Evolving concepts in Xp11 translocation carcinoma, mucinous tubular and spindle cell carcinoma, multilocular cystic clear cell RCC, and carcinoma associated with neuroblastoma are addressed within this review. Tubulocystic carcinoma, thyroid-like follicular carcinoma of kidney, acquired cystic disease-associated RCC, and clear cell papillary RCC are also described. Finally, candidate entities, including RCC with t(6;11) translocation, hybrid oncocytoma/chromophobe RCC, hereditary leiomyomatosis and RCC syndrome, and renal angiomyoadenomatous tumor are reviewed. Knowledge of these new entities is important for diagnosis, treatment and subsequent prognosis. This review provides a targeted summary of new developments in RCC.

Thyroid-like follicular carcinoma of the kidney in a patient with nephrolithiasis and polycystic kidney disease: a case report

Abstract

Thyroid-like follicular carcinoma of the kidney (TLFC), a rare neoplasm with low malignant potential, is histologically similar to primary thyroid follicular carcinoma, but characteristically lacks thyroid immunohistochemical markers. We report a case of 34-year old patient with nephrolithiasis. Ultrasound revealed hepatorenal cysts consistent with adult type polycystic kidney disease (ATPKD) and a cytologically confirmed left kidney tumor. Nephrectomy specimen contained sharply demarcated lesion of unusual morphology. Tubular and cystic structures lined by mostly cuboidal cells and filled with amorphous eosinophillic material, reminiscent of follicular carcinoma of the thyroid gland, were diagnostic for TLFC. Thyroid markers were negative. To our knowledge this is the first report of TFLC associated to ATPKD. Brief review of previously published TFLCs, possible relationship between entities and differential diagnosis are discussed.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/8067946569612694