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

Sarcomatoid and Rhabdoid Renal Cell Carcinoma: Clinical, Pathologic, and Molecular Genetic Features

Renal cell carcinoma (RCC) with sarcomatoid and rhabdoid morphologies has an aggressive biological behavior and a typically poor prognosis. The current 2022 WHO classification of renal tumors does not include them as distinct histologic entities but rather as transformational changes that may arise in a background of various distinct histologic types of RCC. The sarcomatoid component shows malignant spindle cells that may grow as intersecting fascicles, which is reminiscent of pleomorphic undifferentiated sarcoma. The rhabdoid cells are epithelioid cells with eccentrically located vesicular nuclei with prominent nucleoli and large intracytoplasmic eosinophilic inclusions. Studies have shown that RCCs with sarcomatoid and rhabdoid differentiation have distinctive molecular features. Sarcomatoid RCC harbors shared genomic alterations in carcinomatous and rhabdoid components, but also enrichment of specific genomic alterations in the sarcomatoid element, suggesting molecular pathways for development of sarcomatoid growth from a common clonal ancestor. Rhabdoid differentiation also arises through clonal evolution although less is known of specific genomic alterations in rhabdoid cells. Historically, treatment has lacked efficacy, although recently immunotherapy with PD-1/PD-L1/CTLA-4 inhibitors has produced significant clinical responses. Reporting of sarcomatoid and rhabdoid features in renal cell carcinoma is required by the College of American Pathologists and the International Collaboration on Cancer Reporting. This manuscript reviews the clinical, pathologic, and molecular features of sarcomatoid RCC and rhabdoid RCC with emphasis on the morphologic features of these tumors, significance of diagnostic recognition, the molecular mechanisms of tumorigenesis and differentiation along sarcomatoid and rhabdoid lines, and advances in treatment, particularly immunotherapy.

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.

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.

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.

[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).

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.

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.