CAIX and pax-8 Commonly Immunoreactive in Endolymphatic Sac Tumors: A Clinicopathologic Study of 26 Cases with Differential Considerations for Metastatic Renal Cell Carcinoma in von Hippel-Lindau Patients

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.

CAIX Immunostaining in Non-neoplastic Renal Diseases

BACKGROUND/AIM

Carbonic anhydrase 9 (CAIX) is a transmembrane metalloenzyme that regulates cellular adhesion, proliferation, and intra/extracellular pH. It is expressed primarily through a hypoxia-inducible factor 1 (HIF-1)-dependent mechanism. Its over-expression is closely related to somatic mutations in the Von Hippel-Lindau (VHL) gene. Studies have shown that it is over-expressed in renal cell carcinoma. In this study, we aimed to assess the value of CAIX immunostaining as an ancillary diagnostic tool in renal malignancies and medical renal diseases.

PATIENTS AND METHODS

Slides of kidney tumors and medical kidney diseases were selected to evaluate CAIX expression. Intensity and staining patterns of CAIX were independently assessed by two pathologists.

RESULTS

Our results showed strong and diffuse box-like membranous staining pattern in the majority of the clear cell renal cell carcinoma (ccRCC) cases (47/59 cases; 94%). A strong, diffuse cup-shaped staining pattern was observed in clear cell papillary RCC. Variable positivity was observed in other RCC (renal cell carcinoma) subtypes. In non-neoplastic renal conditions, the majority of the cases were negative for CAIX, and only a few cases demonstrated patchy non-specific staining. Of note, a single case of transplanted kidney biopsy taken because of delayed graft function showed a focal area of dilated tubules lined by cells with clear cytoplasm and enlarged nuclei with prominent nucleoli. This area showed diffuse membranous staining for CAIX.  Two cases of end-stage renal disease showed a focal circumferential membranous staining pattern for CAIX in dilated tubules.

CONCLUSION

The CAIX immunoreactivity observed in these three cases could be indicative of an early-stage renal cell neoplasm and warrants further investigation.

Immunohistochemical Expression Pattern of Theragnostic Targets SSTR2 and PSMA in Endolymphatic Sac Tumors: A Single Institution Case Series

BACKGROUND

Endolymphatic sac tumors are rare neoplasia characterized by slow growth. However, their clinical impact should not be underestimated, considering their potential for local aggressive behavior and strong association with von Hippel-Lindau syndrome. Therefore, early detection with emerging theragnostic examinations such as ⁶⁸Ga-DOTATATE-PET/CT might improve patient management and reduce morbidity.

METHODS

We report the clinicopathological features of seven endolymphatic sac tumors. In this cohort, we performed immunohistochemical analysis of somatostatin receptor 2A (SSTR2A) and prostate specific membrane antigen (PSMA) protein expression patterns; two targets providing rationale for novel imaging modalities such as PSMA- or SSTR-targeted PET.

RESULTS

The tumor cells of all cases were negative for prostate specific membrane antigen and somatostatin receptor 2A, however immunolabeling was consistently detected in intratumoral endothelial cells of endolymphatic sac tumors for PSMA (7/7 cases, 100%), and for SSTR2A (5/7 cases, 71%).

CONCLUSIONS

Our results show a high rate of PSMA and SSTR2A expression in the tumor vasculature of endolymphatic sac tumors. PSMA and SSTR2A can be targeted with appropriate radioligands for diagnostic and therapeutic purposes. This finding provides a rationale for prospective clinical studies to test this approach as a sensitive screening tool for patients with suspected endolymphatic sac tumors including an improved management of von Hippel-Lindau syndrome.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumours: Tumours of the Ear

In the recently published 5th Edition of the World Health Organisation Classification of Head and Neck Tumours, there are relatively few changes to report in terms of nomenclature in lesions of ear and temporal bone and fewer developments in molecular pathogenesis in comparison to other sites, particularly in sinonasal tract. Ear and temporal bone tumours are rare and biopsy material is limited. As a result, resources in the literature are scarce with few large series, no controlled clinical trials and the approaches to staging and management are not standardised. New entities are difficult to characterise. The number of entries has, however, increased for tumours of the ear and temporal bone (thirteen) compared to the 4th Edition (eleven). Some lesions previously included in the 4th Edition considered to have no site-specific features have been excluded to be discussed elsewhere and other benign lesions that are specific to this site have been included. The tumours and tumour-like entities of ear and temporal bone are discussed here mindful that the chapter in the 5th edition better correlates disease processes with clinical information and imaging and as far as possible standardises nomenclature.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Familial Tumor Syndromes

The initiative of the 5th edition of the WHO classification of the Head and Neck Tumours establishing a new section dedicated to familial/heritable tumor syndromes with tumors and lesions in the head and neck region was much needed to better understand the tumours, diseases, and associated syndromes, as well as establish recommendations for monitoring and treating these patients. (WHO Classification of Tumours Editorial Board. Head and Neck tumours. Lyon (France): International Agency for Research on Cancer; 2022. https://publications.iarc.fr/ ). Within the newly established chapter on genetic tumor syndromes, we have described the main manifestations on the head and neck region in 15 syndromes. This review highlights the important findings within these syndromes, especially on the update on syndromes with tumors involving the head and neck region, as Gorlin syndrome/nevoid basal cell carcinoma syndrome associated with odontogenic keratocysts; Brooke-Spiegler syndrome/familial cylindromatosis and the associated membranous-type salivary gland basal cell adenoma, PTEN hamartoma tumor syndrome/Cowden syndrome with associated facial skin and mucosal lesions and characteristic multinodular thyroid lesions, Von Hippel Lindau syndrome and the associated middle ear endolymphatic sac tumor, as well as the fascinating genetic aspects of the diverse Head and Neck Paragangliomas. We will also discuss hyperparathyroidism-jaw tumor syndrome is characterized by parathyroid tumors in association with fibro-osseous jaw tumors, as well as head and neck desmoid tumors associated with familial adenomatous polyposis with Gardner syndrome variant familial, multicentric head and neck squamous cell carcinoma, tuberous sclerosis and neurofibromatosis type 1-associated head and neck lesions.

Molecular characterisation of sporadic endolymphatic sac tumours and comparison to von Hippel-Lindau disease-related tumours

AIMS

Although inactivation of the von Hippel-Lindau gene (VHL) on chromosome 3p25 is considered to be the major cause of hereditary endolymphatic sac tumours (ELSTs), the genetic background of sporadic ELST is largely unknown. The aim of this study was to determine the prevalence of VHL mutations in sporadic ELSTs and compare their characteristics to VHL-disease-related tumours.

METHODS

Genetic and epigenetic alterations were compared between 11 sporadic and 11 VHL-disease-related ELSTs by targeted sequencing and DNA methylation analysis.

RESULTS

VHL mutations and small deletions detected by targeted deep sequencing were identified in 9/11 sporadic ELSTs (82%). No other cancer-related genetic pathway was altered except for TERT promoter mutations in two sporadic ELST and one VHL-disease-related ELST (15%). Loss of heterozygosity of chromosome 3 was found in 6/10 (60%) VHL-disease-related and 10/11 (91%) sporadic ELSTs resulting in biallelic VHL inactivation in 8/10 (73%) sporadic ELSTs. DNA methylation profiling did not reveal differences between sporadic and VHL-disease-related ELSTs but reliably distinguished ELST from morphological mimics of the cerebellopontine angle. VHL patients were significantly younger at disease onset compared to sporadic ELSTs (29 vs. 52 years, p < 0.0001, Fisher's exact test). VHL-disease status was not associated with an increased risk of recurrence, but the presence of clear cells was found to be associated with shorter progression-free survival (p = 0.0002, log-rank test).

CONCLUSION

Biallelic inactivation of VHL is the main mechanism underlying ELSTs, but unknown mechanisms beyond VHL may rarely be involved in the pathogenesis of sporadic ELSTs.

Endolymphatic sac tumor: single-institution series of seven cases with updated review of literature

BACKGROUND

Endolymphatic sac tumour (ELST) is a rare low-grade locally aggressive neoplasm arising from the endolymphatic duct or sac. It presents mostly with vestibulo-cochlear symptoms either sporadically or as part of von Hippel-Lindau (VHL) syndrome. Micro-neurosurgical excision remains the cornerstone of therapy with the role of radiotherapy (RT) being controversial. This is a clinico-pathological analysis of consecutive ELST patients presenting to a single-institution in India.

METHODS

Neuropathology database of a tertiary-care comprehensive cancer centre was searched electronically to identify consecutive patients with histopathological diagnosis of ELST registered at the institute over last one decade. Data regarding demographic profile, clinical presentation, histopathological features, treatment details and outcomes were retrieved from electronic medical records for this retrospective analysis.

RESULTS

Electronic search identified seven unique patients with biopsy-proven ELST registered at the institute between 2009 and 2020. Median age of the study cohort was 39 years (range 24-65 years) with strong male predilection (5:2 ratio) and left-sided preponderance (71%). Most common presenting symptoms were hearing loss (86%) and earache (71%) on affected side followed by headache (43%). All patients underwent maximal safe resection at initial diagnosis and were followed-up closely with periodic surveillance imaging. Two patients underwent salvage RT using high-precision conformal techniques at recurrence/progression.

CONCLUSION

ELST is a rare low-grade locally aggressive neoplasm that arises generally as part of VHL syndrome or sometimes sporadically. Gross total resection provides the best chance of cure with RT being reserved for unresectable disease, large residue, medical inoperability, or as salvage therapy for recurrent/progressive tumor.

Clear cell papillary renal cell carcinoma: an update after 15 years

Fifteen years since the first recognition of clear cell papillary renal cell carcinoma, this distinct renal tumour type is now well accepted as a distinct entity in major classification schemes. It occurs both with and without end-stage renal disease and may be multifocal or bilateral in both scenarios. Recognisable morphological features include clear cells lining branching glands and variable papillary formations with nuclear alignment. Most tumours are small (pT1a) and nucleolar grade 1-2. Immunohistochemistry consistently shows positivity for carbonic anhydrase IX and cytokeratin 7, and often high molecular weight cytokeratin or GATA3, the latter suggesting distal nephron phenotype. Labeling for AMACR and CD10 is consistently negative or minimal. Despite a resemblance to clear cell renal cell carcinoma, molecular alterations of VHL and chromosome 3p are typically lacking, with debatable rare exceptions. Potential mimics include clear cell renal cell carcinoma (with branching architecture or nuclear alignment), papillary renal cell carcinoma with clear cytoplasm, or rarely MITF family translocation renal cell carcinoma. Clinical behaviour is highly favourable with rare, debatable reports of aggressive behaviour. Combined with striking similarity to several extrarenal benign neoplasms, it would be reasonable to reclassify this entity as a benign or low malignant potential neoplasm. Using the nomenclature of the extrarenal counterparts, clear cell papillary (cyst)adenoma is proposed.

Papillary-cystic neoplasms of the middle ear are distinct from endolymphatic sac tumours

AIMS

Papillary neoplasms of the middle and inner ear are rare and poorly characterised. The current World Health Organization classification divides them into two major subtypes: aggressive papillary tumours (APTs) and endolymphatic sac tumours (ELSTs). The aim of this article is to present two papillary neoplasms of the middle ear that do not fit into either the classic APT category or the classic ELST category, and compare them with three ELSTs.

METHODS AND RESULTS

The patients were a 48-year-old female and a 59-year-old male without a history of other neoplasms. Histology showed papillary-cystic growth of predominantly oncocytic (Case 1) or mucinous (Case 2) cells surrounded by a p63-positive basal layer. The overall histology was reminiscent of oncocytic sinonasal papilloma (Case 1) and pancreatobiliary or salivary intraductal papillary mucinous neoplasms (Case 2). Ovarian-type stroma, invasion and malignant features were absent. Immunohistochemistry revealed expression of cytokeratin (CK) 7, but not carbonic anhydrase IX (CAIX) or paired box gene 8 (PAX8) (except for very focal PAX8 expression in Case 1). The TST15 gene panel and HRAS sequencing revealed no pathogenic mutations in BRAF, KRAS, EGFR, AKT1, or HRAS. The TruSight RNA fusion panel revealed an MKRN1-BRAF fusion in Case 1. No fusion was detected in Case 2. The three ELSTs showed classic features of the entity, expressed CK7, epithelial membrane antigen, PAX8, and CAIX, and lacked a basal cell layer.

CONCLUSION

These novel cases suggest that papillary tumours of the ear represent a heterogeneous spectrum of distinct neoplasms unified by a prominent papillary-cystic pattern rather than a single entity. Future studies should clarify whether the MKRN1-BRAF fusion is a defining recurrent driver event, especially in those cases reported as sinonasal-type middle ear papillomas.

The endolymphatic sac tumor: challenges in the eradication of a localized disease

OBJECTIVE

Identify the critical points that lead to recurrences and lack of radicality in endolymphatic sac tumors (ELSTs).

STUDY DESIGN

Retrospective case study and review of the literature.

SETTING

Tertiary referral center.

PATIENTS

Thirteen cases of ELST were included in the study and their preoperative, intraoperative and postoperative data were analyzed and compared to a review of the literature.

INTERVENTION(S)

Therapeutical.

MAIN OUTCOME MEASURE(S)

Prevalence of recurrent and residual tumors, comparison to the literature and analysis of ELST characteristics.

RESULTS

Diagnosis was made 26 ± 17 months after the onset of symptomatology, and an ELST was preoperatively suspected in only six cases. At the time of surgery, 10 patients suffered from hearing loss. Preoperative symptoms or audiometry could not predict labyrinth infiltration, although speech discrimination scores were significantly associated with labyrinth infiltration (p = 0.0413). The labyrinth was infiltrated in 8 cases (57.1%), and in 7 cases (46.7%) the tumor eroded the carotid canal, whereas 6 cases (40%) presented an intradural extension. A gross total resection was achieved in 11 cases. There were two residual tumors, one of which because of profuse bleeding, and one recurrence (23.1%). A mean of 22.8% of recurrent or residual tumors are described in the literature based on 242 published cases, in more than half of the cases as a consequence of subtotal tumor resection (STR).

CONCLUSIONS

Recurrence derives mostly from the difficulty to identify the extension of the tumor due to the extensive bone infiltration. Accurate diagnosis and correct preoperative planning, with embolization when possible, will facilitate surgery and avoid STR due to intraoperative bleeding. Long follow-ups are important in order to avoid insidious recurrences.