PAX8 expression in sporadic hemangioblastoma of the kidney supports a primary renal cell lineage: implications for differential diagnosis

Recurrent Tuberous Sclerosis Complex/Mammalian Target of Rapamycin Mutations Define Primary Renal Hemangioblastoma as a Unique Entity Distinct From Its Central Nervous System Counterpart

ABSTRACT

Renal hemangioblastoma (HB) is a rare subset of HBs arising outside of the central nervous system (CNS), with its molecular drivers remaining entirely unknown. There were no significant alterations detected in previous studies, including von Hippel-Lindau gene alterations, which are commonly associated with CNS-HB. This study aimed to determine the real molecular identity of renal HB and better understand its relationship with CNS-HB. A cohort of 10 renal HBs was submitted for next-generation sequencing technology. As a control, 5 classic CNS-HBs were similarly analyzed. Based on the molecular results, glycoprotein nonmetastatic B (GPNMB) immunohistochemistry was further performed in the cases of renal HB and CNS-HB. Mutational analysis demonstrated that all 10 renal HBs harbored somatic mutations in tuberous sclerosis complex 1 ( TSC1 , 5 cases), TSC2 (3 cases), and mammalian target of rapamycin (2 cases), with the majority classified as pathogenic or likely pathogenic. The CNS-HB cohort uniformly demonstrated somatic mutations in the von Hippel-Lindau gene. GPNMB was strong and diffuse in all 10 renal HBs and completely negative in CNS-HBs, reinforcing the molecular findings. Our study reveals a specific molecular hallmark in renal HB, characterized by recurrent TSC/mammalian target of rapamycin mutations, which defines it as a unique entity distinct from CNS-HB. This molecular finding potentially expands the therapeutic options for patients with renal HB. GPNMB can be considered for inclusion in immunohistochemical panels to improve renal HB identification.

Polycythemia Secondary to Renal Hemangioblastoma: A Case Report and Literature Review

Secondary polycythemia is a paraneoplastic syndrome observed in tumors with excessive erythropoietin (EPO) production. Renal cell carcinoma (RCC) and cerebellar hemangioblastoma are the 2 most well-known tumors to induce secondary polycythemia. Hemangioblastomas occurring in the kidney are rare. In this work we present a case of renal hemangioblastoma that caused erythrocytosis in a 19-year-old man. We demonstrated intratumoural EPO production by immunohistochemistry, and conducted whole-exome sequencing to evaluate possible genetic alterations that reported to induce tumor-related polycythemia. In spite of an indolent clinical behavior, renal hemangioblastoma is difficult to differentiate from RCC not only clinically, but also histopathologically. Given that RCC is the most well-known renal tumor to induce erythrocytosis, the uncommon manifestation of polycythemia in renal hemangioblastoma, as shown in our case, can cause further diagnostic challenges. Renal hemangioblastoma should be listed in the differential diagnoses of renal tumors presenting with erythrocytosis, apart from the most common RCC.

Clinicopathological and molecular features of renal cell carcinomas with haemangioblastoma-like features distinct from clear cell renal cell carcinoma

AIMS

Haemangioblastomas arise in the central nervous system. Rarely, haemangioblastomas may develop in extra-neural sites, such as the kidneys. A few reported cases of renal cell carcinomas (RCCs) with haemangioblastoma-like features have exhibited both clear cell renal cell carcinoma (CCRCC)- and haemangioblastoma-like components. The clinicopathological and molecular characteristics of RCCs with haemangioblastoma-like features were analysed, focusing on VHL alterations, in comparison with CCRCCs partially resembling haemangioblastoma.

METHODS AND RESULTS

Four RCCs with haemangioblastoma-like features and five CCRCCs partially resembling haemangioblastoma were included. The RCCs with haemangioblastoma-like features were indolent and lacked adverse prognostic factors. All RCCs with haemangioblastoma-like features had a well-circumscribed appearance and a thick fibromuscular capsule, with fibromuscular bundles extending into the tumour to varying degrees in the three tumours. Each RCC with haemangioblastoma-like features exhibited CCRCC-like areas with indistinct tubular structures and foci of haemangioblastoma-like areas, in which vessels and short spindle cells overwhelmed tumour cells. Whereas haemangioblastoma-like areas in the CCRCCs partially resembling haemangioblastoma exhibited sparse vessels and spindle cells and distinct clear cells. The RCCs with haemangioblastoma-like features exhibited a unique immunohistochemical profile, with positive staining for inhibin-α, S100, carbonic-anhydrase-9, keratin7, and high molecular weight keratin and negative staining for (alpha-methylacyl-CoA racemase) AMACR. RCC with haemangioblastoma-like features did not display any VHL alterations, including VHL mutation, 3p LOH, and methylation of the VHL promoter region, and the two tumours harboured a likely oncogenic missense variant of MTOR (c.7280T>G).

CONCLUSION

The histopathological, immunohistochemical, and molecular findings suggest that RCC with haemangioblastoma-like features is a distinct entity from CCRCC.

Current Knowledge and Prospects for Renal Hemangioblastoma and Renal Cell Carcinoma with Hemangioblastoma-like Features

Tumors exhibiting histopathological findings similar to those of hemangioblastoma of the central nervous system (CNS-HB) rarely develop in the kidneys. Currently, renal hemangioblastoma (RHB) is considered analogous to CNS-HB; however, they differ in gross appearance, as well as immunohistochemical and molecular findings. In contrast, some renal cell carcinomas reportedly comprise distinct, clear cell renal cell carcinoma (CCRCC)- and hemangioblastoma (HB)-like areas. Initially, renal cell carcinomas with HB-like features (RCC-HBs) were considered a morphological variant of CCRCC owing to their diverse histological findings. However, the immunohistochemical and molecular findings of RCC-HBs suggest that RCC-HB is distinct from CCRCC. Additionally, one of the RCC-HBs had a focal leiomyomatous stroma and TSC2 variant, suggesting that RCC-HB and RCC with fibromyomatous stroma (RCC-FMS) might belong to the same disease entity. Therefore, we comprehensively reviewed the clinical, pathological, and molecular features of RHB, RCC-HB, and the related tumors and discussed the similarities, differences, and relationships between them. We believe that our review would serve as a foundation for further investigation on elucidating the relationship between CNS-HB, RHB, RCC-HB, and RCC-FMS.

Primary hemangioblastoma of the kidney with molecular analyses by next generation sequencing: a case report and review of the literature

Background

Hemangioblastoma is an indolent mesenchymal tumor most frequently occurring in the central nervous system (CNS), but can also arise extraneuraxially, as part of Von Hippel-Lindau (VHL) disease or in sporadic tumors. Extraneuraxial hemangioblastomas occur outside the central nervous system. It includes tumors arising from the nervous paraneuraxial structures and visceral organs. Sporadic hemangioblastoma of the kidney, a rare subset of extraneuraxial hemangioblastomas, is an under-recognized renal neoplasm. There have been only 25 cases described to date in the English language literature. We report herein one additional sporadic tumor in a patient without VHL disease.

Case presentation

A 61 year old male presenting with gross hematuria was found to have a 3.5 cm renal mass at the lateral mid to lower pole of the left kidney on computed tomography urogram. The patient underwent a partial nephrectomy for the mass. Pathological examination showed a well-circumscribed non-encapsulated tumor composed of sheets of large polygonal cells traversed by a rich vascular network. The tumor cells showed clear to eosinophilic cytoplasm and overall bland nuclei. The diagnosis of hemangioblastoma was confirmed by positive immunostaining for alpha-inhibin, S100, neuron-specific enolase, and PAX8. No significant gene mutations, including VHL gene and copy number changes were detected in the tumor using next generation sequencing supporting the diagnosis of sporadic renal hemangioblastoma.

Conclusion

Sporadic renal hemangioblastoma is a rare subset of extraneuraxial hemangioblastomas. We report one such tumor in a patient without clinical or molecular evidence of VHL disease. The literature was reviewed to better understand the clinical, radiological, pathological, and molecular features of this neoplasm. The majority of renal hemangioblastomas showed positive immunostaining for PAX8, which supports the idea that the immunoprofiles of extraneuraxial hemangioblastomas can vary depending on sites of origin. Diagnosis of renal hemangioblastoma is challenging because of its rarity and overlapping microscopic and immunophenotypic features with other renal tumors, including clear cell renal cell carcinoma. In some cases, molecular or genetic studies may be necessary to obtain an accurate diagnosis. Since renal hemangioblastoma is clinically benign, recognition of this pathological entity is important to avoid unnecessary over-treatment.

Sporadic hemangioblastoma of the kidney: a clinicopathologic study of three cases and a literature review

Much attention has been paid to renal hemangioblastoma, but there are still challenges in its differential diagnosis. Three cases (2 men, 1 woman; age: 40–56 years) presented with renal tumors. The tumors were surrounded by a thick fibrous capsule, well-demarcated from the surrounding renal parenchyma, and composed of sheets or nests of polygonal to short spindle-shaped tumor cells with a rich capillary network. In cases 1 and 3, the large polygonal tumor cells contained abundant pale or eosinophilic cytoplasm, and some possessed intracytoplasmic lipid vacuoles. In case 2, tumor cells were characterized by a uniform size, mild, clear, or lightly stained cytoplasm, and typical "clear cell" appearance. Immunohistochemistry revealed that the polygonal stromal cells were strongly and diffusely positive for α-inhibin, neuron-specific enolase (NSE), S100 protein, and vimentin. Cluster of differentiation (CD)10 and paired box gene (PAX)8 were positive, while epithelial membrane antigen (EMA) and cytokeratin (CK) were focally positive in case 3. CD34 and CD31 outlined the contours and distribution of the vascular networks. Renal hemangioblastoma is rare and prone to misdiagnosis; more attention should be paid to the morphological features and reasonable application of immunohistochemistry in the diagnosis of hemangioblastoma.

CT and MRI characteristic findings of sporadic renal hemangioblastoma: Two case reports

RATIONALE

Hemangioblastomas in the kidney are rare. Although a few cases of renal hemangioblastoma (RH) have been reported, the content of these articles mainly focused on clinical and pathological research, with minimal descriptions of radiologic findings. Moreover, there are no descriptions of magnetic resonance imaging (MRI) with enhancement of this condition. Herein, we report 2 cases of RH with computed tomography (CT) and MRI findings.

PATIENT CONCERNS

Two patients presented to our institution because of dull pain in the left abdomen, and a mass in the left kidney was found by ultrasound examination in each case. The patient had no special family history. Physical examination revealed no obvious tenderness or percussion pain in the renal and ureteral walking areas, and there was no obvious mass. Routine blood and urine tests were normal, and the serum tumor markers were negative. No obvious lesions were found on imaging of the other body parts.

DIAGNOSIS

Similar radiologic findings were observed in both cases and mimicked those of cavernous hemangiomas of the liver, including peripheral nodular enhancement in the corticomedullary phase, progressive centripetal enhancement in the nephrographic and delayed phases, and occasional complete "filling in" in the delayed phase. We made a radiologic diagnosis of renal clear cell carcinoma for patient 1 and suspected renal clear cell carcinoma for patient 2, but the pathological results showed RH.

INTERVENTIONS

Given the suspicion of renal cell carcinoma, both patients underwent partial nephrectomy.

OUTCOME

The recovery of the two patients was uneventful, and there was no evidence of local recurrence or metastasis many years after surgery.

LESSONS

RH is a rare benign tumor that can be easily misdiagnosed as clear cell carcinoma. Characteristic CT and MRI manifestations may improve preoperative diagnostic accuracy to avoid surgery or indicate nephron-sparing surgery.

Sporadic renal hemangioblastoma: A case report of a rare benign renal tumor

In renal tumors, suspicious for renal cell carcinoma, where there is any doubt and discrepancy between morphology and immune profile, we recommend performing further immunohistochemical staining for pan-cytokeratin, S100, NSE, and inhibin-alpha. Thus, follow-up overtreatment can be avoided in cases of benign kidney tumors.

Renal Cell Carcinoma With Hemangioma-Like Features: Diagnostic Implications and Review of the Literature

Renal cell carcinoma (RCC) with clear cell morphology may show a prominent delicate vascularity. In this article, we report the morphologic and immunohistochemical features of a clear cell papillary RCC mimicking hemangioblastoma and a clear cell RCC mimicking hemangioma. Case 1 showed tubular and papillary growth of clear cells with distinctive areas of capillary proliferation and admixed stromal-like cells resembling a hemangioblastoma. Case 2 consisted of homogeneously delicate microvascular proliferations resembling a capillary hemangioma with scattered inconspicuous clear cells. The clear cells of Case 1 were PAX8(+), CK7(diffuse+), CA9(diffuse+, cup-shaped), and inhibin A(−). The hemangioblastoma-like areas were PAX8(+), CK7(−), CA9(diffuse+), and inhibin A(diffuse+). Case 2 showed PAX8(+), CK7(−), and CA9(diffuse+). They can be diagnostically challenging, and it is important to recognize that a pure hemangioma or hemangioblastoma of the kidneys is very rare, and that RCCs with clear cell morphology rarely exhibit hemangioma-like characteristics.

Extraneuraxial Hemangioblastoma: Clinicopathologic Features and Review of the Literature

Extraneuraxial hemangioblastoma occurs in nervous paraneuraxial structures, somatic tissues, and visceral organs, as part of von Hippel-Lindau disease (VHLD) or in sporadic cases. The VHL gene plausibly plays a key role in the initiation and tumorigenesis of both central nervous system and extraneuraxial hemangioblastoma, therefore, the underlying molecular and genetic mechanisms of the tumor growth are initially reviewed. The clinical criteria for the diagnosis of VHLD are summarized, with emphasis on the distinction of sporadic hemangioblastoma from the form fruste of VHLD (eg, hemangioblastoma-only VHLD). The world literature on the topic of extraneuraxial hemangioblastomas has been comprehensively reviewed with ∼200 cases reported to date: up to 140 paraneuraxial, mostly of proximal spinal nerve roots, and 65 peripheral, 15 of soft tissue, 6 peripheral nerve, 5 bone, and 39 of internal viscera, including 26 renal and 13 nonrenal. A handful of possible yet uncertain cases from older literature are not included in this review. The clinicopathologic features of extraneuraxial hemangioblastoma are selectively presented by anatomic site of origin, and the differential diagnosis is emphasized in these subsets. Reference is made also to 10 of the authors' personal cases of extraneuraxial hemangioblastomas, which include 4 paraneuraxial and 6 peripheral (2 soft tissue hemangioblastoma and 4 renal).

Updates in Benign Lesions of the Genitourinary Tract

The genitourinary tract is a common site for new cancer diagnosis, particularly for men. Therefore, cancer-containing specimens are very common in surgical pathology practice. However, many benign neoplasms and nonneoplastic, reactive, and inflammatory processes in the genitourinary tract may mimic or cause differential diagnostic challenges with malignancies. Emerging clinicopathologic, immunohistochemical, and molecular characteristics have shed light on the pathogenesis and differential diagnosis of these lesions. This review addresses differential diagnostic challenges related to benign genitourinary tract lesions in the kidney, urinary bladder, prostate, and testis, with emphasis on recent advances in knowledge and areas most common in diagnostic practice.

Evaluation of PAX8 Expression and Its Potential Diagnostic and Prognostic Value in Renal and Extra-Renal Ewing Sarcomas/PNETs

PAX8 is a transcription factor involved in the regulation of organogenesis of the thyroid gland, kidney, and Müllerian system. It is commonly expressed in epithelial tumors of thyroid and parathyroid glands, kidney, thymus, and female genital tract. PAX8 is increasingly used in the establishment of tissue of origin in carcinomas and has recently been identified in a subset of small blue round cell tumors including Ewing sarcomas/PNETs. However, it is unclear if this association in ES/PNETs is due to renal origin or is PNET specific. In this study we investigated the PAX8 staining pattern of primary renal and extra-renal ES/PNETs to explore its potential diagnostic and prognostic role. A tissue microarray (TMA) of 22 cases of extra-renal Ewing/PNETs and two separate cases of primary renal PNET whole slide sections were immunohistochemically stained with rabbit polyclonal PAX8 antibody. PAX8 was positive in 2 of 2 primary renal PNETs and in 14 (64 %) cases of the extra renal PNETs. The association between PAX8 immunoreactivity and Ewing/PNET was identified in both primary renal and extra-renal Ewing/PNETs for the first time. Further studies are warranted to verify these findings and to shed light in the tumorigenesis of Ewing/PNET. However, PAX8 is not useful in establishing a diagnosis of Ewing/PNET due to its presence in different tumors like carcinomas, lymphomas and sarcomas. PAX8 does not seem to have prognostic value.