Useful immunohistochemical markers in differentiating hemangioblastoma versus metastatic renal cell carcinoma

von Hippel-Lindau disease-related neoplasia with an emphasis on renal manifestations

von Hippel-Lindau (VHL) disease is characterized by biallelic inactivation of the VHL gene leading to abnormal or absent VHL protein function, and constitutive activation of hypoxia-inducible factors (HIF) that leads to pro-tumorigenic signaling. Individuals with VHL disease develop numerous cysts and tumors involving multiple organs including the kidneys, central nervous system, endolymphatic sac, lungs, pancreatobiliary system, adrenal glands, epididymis, and/or broad ligament. On histologic examination, these lesions show morphologic overlap as they are frequently characterized by cells with clear cytoplasm and prominent vascularity. In addition to distinguishing non-renal tumors from metastatic clear cell renal cell carcinoma, understanding site-specific histopathologic and immunophenotypic features of these tumors has several applications. This includes distinguishing VHL-related tumors from those that arise sporadically and lack VHL gene alterations, guiding further genetic workup, and helping distinguish between different genetic predisposition syndromes. In this context, immunohistochemical studies for markers such as paired box 8 (PAX-8), carbonic anhydrase 9 (CA9), and glucose transporter 1 (GLUT-1) have an important role in routine clinical practice and represent cost-effective diagnostic tools. The recent development of targeted therapeutics directed against HIF-mediated signaling represents a significant milestone in the management of VHL disease and highlights the importance of accurately diagnosing and characterizing the wide spectrum of VHL disease-associated lesions.

Supratentorial Hemangioblastoma in Adults: A Systematic Review and Comparison of Infratentorial and Spinal Cord Locations

BACKGROUND

Supratentorial hemangioblastomas are benign and highly vascularized neoplasms that appear most often in the spine and posterior cranial fossa. They can also be located in the supratentorial compartment of the brain. We conducted a systematic review of the literature to better understand the clinical insights of supratentorial hemangioblastoma in adults.

METHODS

Using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, the authors reviewed the English-language literature in the PubMed/MEDLINE database on supratentorial hemangioblastoma in adults, published in the past 40 years. We analyzed the differences between sporadic hemangioblastomas and hemangioblastomas associated with von Hippel-Lindau disease. In addition, we compared the characteristics of supratentorial hemangioblastomas with infratentorial and spinal cord locations.

RESULTS

We reviewed 92 articles, describing 157 supratentorial hemangioblastomas in a total cohort of 148 adult patients. Most articles reporting supratentorial hemangioblastomas were published in the United States. Supratentorial hemangioblastomas occur more frequently in women than men. The median age at the time of diagnosis was 44.48 years. The sellar/parasellar region was the most commonly tumor location, while the most common morphological type was the solid type. Almost 80% of hemangioblastomas were completely resected; the outcome was favorable in more than 3 fourth of patients.

CONCLUSIONS

Given their rarity, the literature on supratentorial hemangioblastomas is limited and based mostly on case reports. Complete surgical resection is the first choice of treatment and is associated with a good treatment outcome.

Jean S, Lovell S, Levine J, Gremillion C, Summers B, Rech RR. Case report: Hemangioblastoma in the brainstem of a dog

A 3-year-old castrated male, American Pit Bull Terrier presented to Texas A&M University due to a 3-week mixed cerebellar and general proprioceptive ataxia, circling, head tilt, and dull mentation. Neurologic examination revealed signs of vestibular and mesencephalic dysfunction. Postmortem examination revealed a 1.1 × 1 × 0.8-cm, soft, dark red, well-circumscribed, left-sided mass, extending from the crus cerebri of the midbrain caudally to the pons. Microscopically, the neoplasm was composed of a spindle-shaped interstitial population of cells interspersed between a prominent capillary network, consistent with the reticular pattern of hemangioblastoma. Interstitial cells had strong, diffuse, intracytoplasmic immunolabeling for neuron-specific enolase (NSE) and were variably positive for intracytoplasmic glial fibrillary acidic protein (GFAP). Vascular endothelial cells had strong diffuse, intracytoplasmic immunolabeling for von Willebrand factor (VWF) glycoprotein. To date, only six cases of hemangioblastoma have been reported in canines, five in the spinal cord, and one in the rostral cerebrum. Our case may represent the first canine hemangioblastoma localized to the brainstem.

Neuropathologic features of central nervous system hemangioblastoma

Hemangioblastoma is a benign, highly vascularized neoplasm of the central nervous system (CNS). This tumor is associated with loss of function of the VHL gene and demonstrates frequent occurrence in von Hippel-Lindau (VHL) disease. While this entity is designated CNS World Health Organization grade 1, due to its predilection for the cerebellum, brainstem, and spinal cord, it is still an important cause of morbidity and mortality in affected patients. Recognition and accurate diagnosis of hemangioblastoma is essential for the practice of surgical neuropathology. Other CNS neoplasms, including several tumors associated with VHL disease, may present as histologic mimics, making diagnosis challenging. We outline key clinical and radiologic features, pathophysiology, treatment modalities, and prognostic information for hemangioblastoma, and provide a thorough review of the gross, microscopic, immunophenotypic, and molecular features used to guide diagnosis.

Transcription factor Fli-1 as a new target for antitumor drug development

The transcription factor Friend leukemia virus integration 1 (Fli-1) belonging to the E26 Transformation-Specific (ETS) transcription factor family is not only expressed in normal cells such as hematopoietic stem cells and vascular endothelial cells, but also abnormally expressed in various malignant tumors including Ewing sarcoma, Merkel cell sarcoma, small cell lung carcinoma, benign or malignant hemangioma, squamous cell carcinoma, adenocarcinoma, bladder cancer, leukemia, and lymphoma. Fli-1 binds to the promoter or enhancer of the target genes and participates in a variety of physiological and pathological processes of tumor cells, including cell growth, proliferation, differentiation, and apoptosis. The expression of Fli-1 gene is related to the specific biological functions and characteristics of the tissue in which it is located. In tumor research, Fli-1 gene is used as a specific marker for the occurrence, metastasis, efficacy, and prognosis of tumors, thus, a potential new target for tumor diagnosis and treatment. These studies indicated that Fli-1 may be a specific candidate for antitumor drug development. Recent studies identified small molecules regulating Fli-1 thanks to our screened strategy of natural products and their derivatives. Therefore, in this review, the advanced research on Fli-1 as a target for antitumor drug development is analyzed in different cancers. The inhibitors and agonists of Fli-1 that regulate its expression are introduced and their clinical applications in the treatment of cancer, thus providing new therapeutic strategies.

Establishment and Characterization of Cell Lines from Primary Culture of Hemangioblastoma Stromal Cells

Context

A well-established cell line of hemangioblastomas (HBs) is still lacking.

Aim

This study aims to explore a stable way to establish primary cell lines of HB stromal cells and investigate the morphological and molecular features of these cells.

Patients and Methods

Specimens of HBs from 13 patients were collected for establishment of primary cell lines of stromal cells. The details on cell culture were described, and the characterizations of cultured cells were conducted by morphological observation, immunocytochemical staining of inhibin-α, brachyury, CD133, CD34, GFAP, CD31, NeuN, CD45, Oligo2, and transmission electron microscopy.

Results

Eleven cases were successfully cultured with a success rate of 84.6%. The cultured cells survived for 10 generations with an estimated doubling time of 77.2 ± 5.89 h. Light microscopy revealed that these cells showed vigorous growth status and presented as polygons or trigons with significant heterogeneity. The immunocytochemical staining showed that inhibin-α, brachyury, CD133, and CD34 were expressed in all the cultured cells, whereas the expression of GFAP, CD31, NeuN, CD45, and Oligo2 was all negative. Transmission electron microscopy confirmed that the cultured cells were stromal cells with typical lipid droplets. The phenomenon of lysosomal autophagy was commonly observed without apoptotic cells in late stage.

Conclusion

Appropriate selection of tumor specimens, short duration of devascularization, ideal digestion time, and nutritious medium are critical points for establishment of primary cell line of HB stromal cells. Stromal cells from both von Hippel-Lindau disease-related HBs and sporadic HBs might originate from embryologically arrested hemangioblasts.

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.

Immunohistochemical Pitfalls in Genitourinary Pathology: 2018 Update

Immunohistochemistry may be a very useful adjunct to morphologic diagnosis in many areas of surgical pathology, including genitourinary pathology. In this review, we address common diagnostic dilemmas where immunophenotypic analysis may be utilized and we highlight pitfalls specific to each scenario. For prostate, we review the diagnosis of limited prostatic adenocarcinoma and the distinction of high-grade prostatic adenocarcinoma from urothelial carcinoma. We also cover markers of urothelial lineage in the diagnosis of metastatic carcinoma of unknown primary site. In the kidney, distinction of poorly differentiated renal cell carcinoma from urothelial carcinoma and epithelioid angiomyolipoma, adjuncts to the recognition of hereditary renal neoplasia, and the diagnosis of metastatic renal cell carcinoma are discussed. Finally, for testis we address distinction of germ cell tumors from sex cord-stromal tumors, as well as the diagnosis of metastatic germ cell tumors.

Isolated hemangioblastoma of the cervical spinal cord: A case report and literature review

INTRODUCTION

Hemangioblastomas are benign, slow growing but highly vascularized tumors of the central nervous system, with the most common location of occurrence in the posterior fossa. Hemangioblastomas usually have an associated with patients that have Von-Hippel Lindau disease, resulting a germline mutation in the VHL tumor suppressor gene. Isolated or sporadic occurrences of hemangioblastomas are much more infrequent and typically respond well after surgery.

PRESENTATION OF CASE

We present case of a 22year old female with worsening shoulder pain, decreased sensation in the hands and feet, and decreasing strength and was found to have a hemangioblastoma of the cervical spine.

DISCUSSION

The patient was treated with surgery and responded well to treatment. We also present a review of the literature on isolated occurrences of hemangioblastomas of the spinal cord.

CONCLUSION

Isolated hemangioblastoma are a rare tumor of the central nervous system and can be managed with surgery.

Neurosurgical Management of Brainstem Hemangioblastomas: A Single-Institution Experience with 116 Patients

OBJECTIVE

Brainstem hemangioblastomas (HBs) are considered one of the most challenging lesions in surgical procedures. We present our institutional experience with 116 patients over a period of 20 years in the treatment of HBs.

METHODS

We evaluated the results of microsurgical treatment and highlighted the management strategies. There were 60 male and 56 female patients including 13 cases with clinical evidence of von Hippel-Lindau disease. Tumors were solid in 99 cases and cystic in 17 cases. Tumors were small (≤2 cm) in 43 cases, large (2-4 cm) in 45 cases, and giant (≥4 cm) in 28 cases.

RESULTS

Radical removal was achieved in 111 patients (95.7%), and incomplete removal was achieved in 5 cases (4.3%). The immediate postoperative mortality and morbidity were 7.8% and 17.2%, respectively. Detailed analyses of outcomes showed that surgical complications were related to some tumor characteristics. Follow-up study was available in 83 patients by Karnofsky performance scale scores. Most patients maintained their preoperative neurologic status. There were 17 patients with surgical disability who demonstrated a clear improvement with rehabilitation treatment. Worsening of neurologic deficits occurred in 2 patients. Ectopic recurrent lesions developed in 2 patients.

CONCLUSIONS

Based on our experience, microsurgery is safe and effective, and excellent outcomes can be obtained for cystic or small tumors. We advocate early surgical intervention for sporadic HBs; giant solid HBs remain a challenge, and meticulous microsurgical technique and perioperative management are vital. Long-term monitoring also is recommended.

Specific immunohistochemical pattern of carbonic anhydrase IX is helpful for the diagnosis of CNS hemangioblastoma

Hemangioblastomas are rare capillary-rich tumors predominantly found in the CNS. The histological appearance of these tumors varies across a broad spectrum. Several entities show considerable histomorphological similarities to hemangioblastomas. Therefore, morphological evaluation can be challenging. In this study, we evaluated the diagnostic utility of immunohistochemistry using antibodies against carbonic anhydrase IX and cytokeratin staining. Within our files, we identified 20 hemangioblastomas. A collection of 46 other tumors relevant to the differential diagnosis (12 pilocytic astrocytomas, 11 meningiomas, one pleomorphic xanthoastrocytoma, one angiomatous fibrous histiocytoma, 14 carcinoma metastases and seven gliomas grades II-IX) served as control. The pattern of strong, diffuse expression of carbonic anhydrase IX with membranous accentuation in combination with keratin negativity was considered diagnostic for hemangioblastomas. It was found in 18 out of 20 (90%) hemangioblastomas and in none of the control cases (P < 0.001). This resulted in a sensitivity of 90% and a specificity of 100%. The positive and negative predictive values were 100% and 96%, respectively. Carbonic anhydrase IX with cytokeratin is thus a highly sensitive and specific marker combination for hemangioblastomas. It is therefore very helpful in the diagnosis of these tumors and in their discrimination from other entities.

A case of cerebellar hemangioblastoma with rhabdoid features

We present an unusual case of cerebellar hemangioblastoma characterized by rhabdoid features. The patient was a 35-year-old Japanese man with occipital neuralgia and exacerbating blurred vision. Magnetic resonance imaging revealed a left posterior cranial fossa tumor, which was isointense on T1-weighted images and hyperintense on T2-weighted images with marked homogeneous enhancement. Histology of the surgically resected tumor showed cellular-type hemangioblastoma with extensive proliferation of rhabdoid cells Immunohistochemistry analysis showed tumor cells positive for inhibin A, CD56, vimentin, INI-1, and vascular endothelial growth factor; negative for PAX8, CD10, epithelial membrane antigen, cytokeratin, (AE1/3), alpha-smooth muscle actin and D2-40; and had focal positivity for glial fibrillary acidic protein and S100. The Ki-67 labeling index was <1 %. Ultrastructural analysis revealed large lipid droplets and abundant intracellular accumulation of intermediate filaments. Based on these findings, the diagnosis was hemangioblastoma with focal rhabdoid features. After a 14-month follow-up, there was no evidence of recurrence. This is the first report of hemangioblastoma with rhabdoid features in the central nervous system. In addition, we discuss the possible pathogenesis.

Ocular Metastatic Renal Carcinoma Presenting With Proptosis

Metastatic renal carcinoma is the third most common source of ocular and second most common source of orbital metastases. This is the first published case of von Hippel-Lindau (vHL) disease that developed renal cell carcinoma metastatic to an eye with a retinal hemangioblastoma. A 73-year-old woman had a history of vHL disease that included prior retinal hemangioblastomas, 2 cerebellar hemangioblastomas, and bilateral renal cell carcinomas with sacral metastasis. After presenting with progressive, painful proptosis secondary to a large mass observable by ocular CT, an enucleation-orbitotomy was performed, and the surgical specimen was sent for histopathological analysis. The ophthalmic renal metastatic tumor, like the primary tumor, was a clear cell variant that involved both the eyeball and orbit in continuity. The intraocular component was larger than the extraocular portion, which was interpreted as an outward extension of an initial retinal metastasis that probably first settled within a hemangioblastoma. Clusters of ectatic ghost vessels with thickened walls produced by periodic acid Schiff-positive, redundant basement membrane material were partially infiltrated by tumor cells at their periphery, thereby lending some support for this hypothesis. Immunohistochemical positivity for the biomarkers cytokeratin 18, vimentin, carbonic anhydrase IX, PAX2, and PAX 8 confirmed the diagnosis. The patient has refused further treatment. Her anophthalmic socket has comfortably retained a porous polyethylene implant without clinical evidence of local recurrence during 5 months of follow up.

Brachyury: a diagnostic marker for the differential diagnosis of chordoma and hemangioblastoma versus neoplastic histological mimickers

Brachyury is a transcription factor which is required for posterior mesoderm formation and differentiation as well as for notochord development during embryogenesis. Due to its expression in the neoplastic cells of chordoma, a malignant tumour deriving from notochordal remnants, but not in tumors showing a similar histology, brachyury has been proposed as a diagnostic marker of this neoplasia. Though commonly considered a hallmark of chordoma, the expression of brachyury has been also documented in the stromal cells of hemangioblastoma (HBL), a slow growing tumor which may involve the central nervous system (CNS) and, rarely, the kidney. Herein we review the role of brachyury immunohistochemical detection in the identification and differential diagnosis of chordoma and HBL towards histological mimickers and suggest that brachyury is added to the panel of immunohistochemical markers for the recognition of HBL in routinary practice, principally in unusual sites.

Renal tumors: diagnostic and prognostic biomarkers

The International Society of Urological Pathology convened a consensus conference on renal cancer, preceded by an online survey, to address issues relating to the diagnosis and reporting of renal neoplasia. In this report, the role of biomarkers in the diagnosis and assessment of prognosis of renal tumors is addressed. In particular we focused upon the use of immunohistochemical markers and the approach to specific differential diagnostic scenarios. We enquired whether cytogenetic and molecular tools were applied in practice and asked for views on the perceived prognostic role of biomarkers. Both the survey and conference voting results demonstrated a high degree of consensus in participants' responses regarding prognostic/predictive markers and molecular techniques, whereas it was apparent that biomarkers for these purposes remained outside the diagnostic realm pending clinical validation. Although no individual antibody or panel of antibodies reached consensus for classifying renal tumors, or for confirming renal metastatic disease, it was noted from the online survey that 87% of respondents used immunohistochemistry to subtype renal tumors sometimes or occasionally, and a majority (87%) used immunohistochemical markers (Pax 2 or Pax 8, renal cell carcinoma [RCC] marker, panel of pan-CK, CK7, vimentin, and CD10) in confirming the diagnosis of metastatic RCC. There was consensus that immunohistochemistry should be used for histologic subtyping and applied before reaching a diagnosis of unclassified RCC. At the conference, there was consensus that TFE3 and TFEB analysis ought to be requested when RCC was diagnosed in a young patient or when histologic appearances were suggestive of the translocation subtype; whereas Pax 2 and/or Pax 8 were considered to be the most useful markers in the diagnosis of a renal primary.

Histologic variations and immunohistochemical features of metastatic clear cell renal cell carcinoma

BACKGROUND

Due to advancements in treatment of metastatic and advanced renal cell carcinoma (RCC), it has become increasingly important to diagnose metastatic RCC and the specific subtype. In this study, we investigated the diverse histologic features of metastatic clear cell renal cell carcinoma (CCRCC) cases in comparison with corresponding primary lesions.

METHODS

We identified 119 metastatic CCRCC cases from 81 corresponding primary lesions diagnosed between 1995 and 2010 and evaluated the diverse histologic and immunohistochemical features of these lesions.

RESULTS

A total of 44 primary lesions (54.3%) had a non-clear cell component in addition to a typical clear cell component. Of the 119 metastatic lesions, 63 lesions (52.9%) contained a non-clear cell component, and 29 metastatic lesions were composed of a non-clear cell component only. Rhabdoid features were the most frequent non-clear cell histology among the metastatic lesions. Metastatic CCRCCs mainly showed positive CD10 and epithelial membrane antigen staining and negative cytokeratin 7 staining.

CONCLUSIONS

Metastatic CCRCC commonly showed a variety of histologic features. If there is a difficulty to diagnose metastatic CCRCC due to a variety of histologic features or small biopsy specimen, histologic review of the primary lesion and immunohistochemical analysis can help determine the correct diagnosis.

Value of PAX8, PAX2, napsin A, carbonic anhydrase IX, and claudin-4 immunostaining in distinguishing pleural epithelioid mesothelioma from metastatic renal cell carcinoma

Both mesotheliomas and renal cell carcinomas can present a wide variety of cytomorphologic features and histologic patterns. Because of this, renal cell carcinomas metastatic to the pleura and lung can be confused with mesotheliomas. Recently, a variety of positive carcinoma markers, including kidney-associated markers, have become available. The aim of this study is to investigate the value of some of these markers, specifically PAX8, PAX2, napsin A, carbonic anhydrase IX, and claudin-4, for assisting in distinguishing pleural epithelioid mesotheliomas from metastatic renal cell carcinomas. To do so, a total of 40 pleural epithelioid mesotheliomas and 55 renal cell carcinomas (33 clear cell, 10 papillary, and 12 chromophobe) were investigated. In all, 91% of the renal cell carcinomas expressed claudin-4, 89% PAX8, 60% PAX2, 71% carbonic anhydrase IX, and 29% napsin A. All of the mesotheliomas were positive for carbonic anhydrase IX and were negative for all of the other markers. On the basis of these results, it is concluded that claudin-4 and PAX8 have a higher sensitivity and specificity for assisting in discriminating between pleural epithelioid mesotheliomas and renal cell carcinomas when compared with all of the other positive carcinoma markers that are, at present, recommended to be included in the immunohistochemical panels used in this differential diagnosis. Even though PAX2 and napsin A are highly specific, because of their low sensitivity, they have only a limited value. Carbonic anhydrase IX is not useful.

Neuropathology of brain metastases

Metastatic tumors are the most common neoplasms encountered in the central nervous system (CNS), and continue to be major cause for mortality and morbidity. Macroscopic features and corresponding radiological findings can be diagnostic in majority of the cases, however, microscopic evaluation would be necessary when the differential diagnosis includes a primary CNS tumor, unknown primary tumor site, and when the resection of the tumor is either considered therapeutic or palliative. The first step in the diagnosis of a metastatic brain lesion is to exclude a primary CNS tumor, followed by verification or identification of the primary tumor and the site. Although general approach to a metastatic lesion from an unknown primary tumor is the same everywhere else, there are slight variations for the metastatic lesions in the CNS versus other regions. When morphological features are not enough to establish a definitive diagnosis, additional studies including immunohistochemical stains are applied. With the expending immunohistochemical armamentarium for pathologists, more accurate assessments are possible even in cases of unknown primary tumor. This review summarizes the diagnostic approach to CNS metastases, immunohistochemical assessment of neoplasm of unknown primary, and primary CNS lesions entering in the differential diagnosis of metastases.

Nervous system involvement in von Hippel-Lindau disease: pathology and mechanisms

Patients with von Hippel-Lindau disease carry a germline mutation of the Von Hippel-Lindau (VHL) tumor-suppressor gene. We discuss the molecular consequences of loss of VHL gene function and their impact on the nervous system. Dysfunction of the VHL protein causes accumulation and activation of hypoxia inducible factor (HIF) which can be demonstrated in earliest stages of tumorigenesis and is followed by expression of VEGF, erythropoietin, nitric oxide synthase and glucose transporter 1 in VHL-deficient tumor cells. HIF-independent functions of VHL, epigenetic inactivation of VHL, pVHL proteostasis, and links between loss of VHL function and developmental arrest are also described. A most intriguing feature in VHL disease is the occurrence of primary hemangioblastic tumors in the nervous system, the origin of which has not yet been entirely clarified, and current hypotheses are discussed. Endolymphatic sac tumors may extend into the brain, but originally arise from proliferation of endolymphatic duct/sac epithelium; the exact nature of the proliferating epithelial cell, however, also has remained unclear, as well as the question why tumors almost consistently develop in the intraosseous portion of the endolymphatic sac/duct only. The epitheloid clear cell morphology of both advanced hemangioblastoma and renal clear cell carcinoma can make the differential diagnosis challenging, recent developments in immunohistochemical differentiation are discussed. Finally, metastasis to brain may not only be caused by renal carcinoma, but may derive from VHL disease-associated pheochromocytoma/paraganglioma, or pancreatic neuroendocrine tumor.

Supratentorial hemangioblastomas: three case reports and review of the literature

Hemangioblastoma (HBL) within the central nervous system is a benign vascular neoplasm that usually occurs in the cerebellum. Supratentorial occurrence of HBL is an extremely rare event. Till date, approximately 129 cases of supratentorial HBL have been reported in the literature. Here, we present three new cases of supratentorial hemangioblatomas, one of which was found to have the lesions in a unique location of the choroidal fissure. The clinical, histopathological, and neuroradiological characteristics, as well as management of this rare disease are discussed with a review of the pertinent literature.

Value of PAX2 immunostaining in tumor diagnosis: a review and update

PAX2 is a member of the PAX family of transcription factors that, together with PAX8, is involved in the regulation of the organogenesis of the kidney and the Müllerian system. Recent investigations have demonstrated that, among tumors, PAX2 is commonly expressed in epithelial tumors of the kidney and female genital tract. Although PAX2 expression has also been reported in B-cell lymphomas and rhabdomyosarcomas, especially alveolar rhabdomyosarcomas, it has been suggested that the positivity in these tumors was most probably due to a cross-reactivity of the anti-PAX2 antibody used in those investigations with other members of the PAX protein family. An analysis of published studies indicates that PAX2 sensitivity for epithelial renal neoplasms and epithelial tumors of the female genital tract is lower than that of PAX8. In contrast to the latter marker, however, PAX2 does not appear to be expressed in epithelial tumors of the thyroid gland or thymus. Because of its restricted expression, PAX2 has proved to be a useful immunohistochemical marker with a wide range of diagnostic applications in surgical pathology, some of which will be briefly reviewed.

Clear cell tumors of the central nervous system: a case-based review

Clear cell tumors of the central nervous system (CNS) encompass a variety of tumor subtypes that are challenging to diagnose given their similar morphologic features. Here, I use a case-based approach to review the clinicopathologic and radiologic features to help guide the general pathologist in the diagnosis of clear cell tumors of the CNS. First, the reader is invited to study 6 images of different CNS tumors with clear cell morphology. Then, each case is expanded in light of clinical and radiologic data and includes a histopathologic description of the tumor. A brief discussion follows with up-to-date diagnostic tools. Finally, I propose an immunohistochemical algorithm to navigate through the complex features that characterize clear cell tumors of the CNS. This review aims to provide a comprehensive approach to diagnosing clear cell neoplasms of the CNS based on improved assessment of the clinicopathologic and radiologic features of each entity.

Expression of brachyury in hemangioblastoma: potential use in differential diagnosis

Hemangioblastoma (HBL) accounts for up to 2.5% of all intracranial tumors. It may occur as a sporadic entity or as a part of Von Hippel-Lindau syndrome. Patients with Von Hippel-Lindau syndrome are also at an increased risk of developing clear cell renal cell carcinoma (CCRCC). The distinction of HBL from CCRCC metastatic to the central nervous system (CNS) or from other histologic mimics can be challenging at times when based solely on hematoxylin and eosin-stained sections. In the present study we evaluated the potential use of the immunohistochemical evaluation of brachyury protein in the differential diagnosis of these lesions. Archival tissues from 22 HBLs, 16 primary CCRCCs, 8 CCRCCs metastatic to the CNS, and 4 angiomatous and 4 clear cell meningiomas were retrieved from our surgical pathology files and submitted to the immunohistochemical procedures against brachyury. Cases showing nuclear and/or cytoplasmic staining were considered to be positive for brachyury. Positive cytoplasmic staining was evidenced in the stromal cells of 20 of the 22 HBLs. In most cases, >50% of the neoplastic cells were labeled, with strong or moderate intensity of staining. No nuclear or cytoplasmic staining for brachyury was observed in any of the primary renal or metastatic CCRCCs, nor in either of the meningioma types. Thus, brachyury cytoplasmic staining was demonstrated to be highly specific for HBL (specificity, 100%) and represented a sensible (sensitivity, 91%) method, with high positive (100%) and negative (89%) predictive values and high diagnostic accuracy (95%) in the differential diagnosis between HBL and CCRCC metastatic to the CNS or meningioma. On the basis of our findings we propose the use of brachyury as an additional helpful immunohistochemical marker to resolve the differential diagnosis of HBL toward histologic mimics.

Value of PAX 8 immunostaining in tumor diagnosis: a review and update

PAX 8 is a transcription factor involved in the regulation of organogenesis of the thyroid gland, kidney, and Müllerian system. Recent studies have shown that, among tumors, PAX 8 is commonly expressed in epithelial tumors of the thyroid and parathyroid glands, kidney, thymus, and female genital tract. Although PAX 8 expression has also been reported in certain neuroendocrine tumors, including well-differentiated pancreatic neuroendocrine tumors, and duodenal and rectal carcinoids, as well as in B-cell lymphomas, it has recently been shown that the PAX 8 positivity reported in these tumors was due to a cross-reactivity of the antibody used with the N-terminal region of PAX 6 and PAX 5, respectively. Owing to its restricted expression, PAX 8 has proved to be a useful immunohistochemical marker with a wide range of diagnostic applications in surgical pathology, some of which are briefly reviewed.

MiRNA-9 and MiRNA-200a distinguish hemangioblastomas from metastatic clear cell renal cell carcinomas in the CNS

Central nervous system (CNS) tumors in von Hippel-Lindau syndrome (VHL) include hemangioblastomas and metastatic clear cell renal cell carcinomas (Met CCRCC). While these tumors often show similar histologic features, differentiating them is of significant importance as Met CCRCC are higher-grade tumors with worse prognosis. No single current immunohistochemical marker unequivocally differentiates between these two entities. MicroRNAs (miRNAs) are noncoding cellular small RNA molecules that play an important role in cancer. We hypothesized that hemangioblastomas and Met CCRCC display distinct miRNA signatures enabling their histologic differentiation. MiRNAs were profiled in 10 cases each of hemangioblastomas, Met CCRCC and primary CCRCC. Ten miRNAs had greater abundance (including miR-9 (∼10-fold) and miR-135a (∼7-fold)) and 39 miRNAs were lower [including miR-200a (∼22-fold) and miR-200b (∼12-fold)] in hemangioblastomas compared with Met CCRCC. Quantitative real-time RT-PCR in 20 hemangioblastomas and 13 Met CCRCC showed a 12-fold increase in miR-9 and a 15-fold decrease of miR-200a in hemangioblastomas compared with Met CCRCC. Finally, in situ hybridization for miR-9 in 15 hemangioblastomas and 10 Met CCRCC confirmed these results. Our data suggest that miR-9 and miR-200a can distinguish between hemangioblastomas and Met CCRCC. Further, these results may also provide insight in understanding the biology of hemangioblastomas.