Mapping of the keratin polypeptides in meningiomas of different types: an immunohistochemical analysis of 463 cases

Proteomic interrogation of the meninges reveals the molecular identities of structural components and regional distinctions along the CNS axis

The meninges surround the brain and spinal cord, affording physical protection while also serving as a niche of neuroimmune activity. Though possessing stromal qualities, its complex cellular and extracellular makeup has yet to be elaborated, and it remains unclear whether the meninges vary along the neuroaxis. Hence, studies were carried-out to elucidate the protein composition and structural organization of brain and spinal cord meninges in normal, adult Biozzi ABH mice. First, shotgun, bottom-up proteomics was carried-out. Prominent proteins at both brain and spinal levels included Type II collagen and Type II keratins, representing extracellular matrix (ECM) and cytoskeletal categories, respectively. While the vast majority of total proteins detected was shared between both meningeal locales, more were uniquely detected in brain than in spine. This pattern was also seen when total proteins were subdivided by cellular compartment, except in the case of the ECM category where brain and spinal meninges each had near equal number of unique proteins, and Type V and type III collagen registered exclusively in the spine. Quantitative analysis revealed differential expression of several collagens and cytoskeletal proteins between brain and spinal meninges. High-resolution immunofluorescence and immunogold-scanning electronmicroscopy on sections from whole brain and spinal cord - still encased within bone -identified major proteins detected by proteomics, and highlighted their association with cellular and extracellular elements of variously shaped arachnoid trabeculae. Western blotting aligned with the proteomic and immunohistological analyses, reinforcing differential appearance of proteins in brain vs spinal meninges. Results could reflect regional distinctions in meninges that govern protective and/or neuroimmune functions.

Proteomic Analysis on Sequential Samples of Cystic Fluid Obtained from Human Brain Tumors

Cystic formation in human primary brain tumors is a relatively rare event whose incidence varies widely according to the histotype of the tumor. Composition of the cystic fluid has mostly been characterized in samples collected at the time of tumor resection and no indications of the evolution of cystic content are available. We characterized the evolution of the proteome of cystic fluid using a bottom-up proteomic approach on sequential samples obtained from secretory meningioma (SM), cystic schwannoma (CS) and cystic high-grade glioma (CG). We identified 1008 different proteins; 74 of these proteins were found at least once in the cystic fluid of all tumors. The most abundant proteins common to all tumors studied derived from plasma, with the exception of prostaglandin D2 synthase, which is a marker of cerebrospinal fluid origin. Overall, the protein composition of cystic fluid obtained at different times from the same tumor remained stable. After the identification of differentially expressed proteins (DEPs) and the protein-protein interaction network analysis, we identified the presence of tumor-specific pathways that may help to characterize tumor-host interactions. Our results suggest that plasma proteins leaking from local blood-brain barrier disruption are important contributors to cyst fluid formation, but cerebrospinal fluid (CSF) and the tumor itself also contribute to the cystic fluid proteome and, in some cases, as with immunoglobulin G, shows tumor-specific variations that cannot be simply explained by differences in vessel permeability or blood contamination.

Nuclear CRX and FOXJ1 Expression Differentiates Non-Germ Cell Pineal Region Tumors and Supports the Ependymal Differentiation of Papillary Tumor of the Pineal Region

Papillary tumor of the pineal region (PTPR) is a neuroepithelial neoplasm first described in 2003. Despite the anatomic association of PTPR with the pineal gland, the features of these tumors resemble those of the ependymal circumventricular subcommissural organ (SCO) of the posterior third ventricle. Given the presumed distinct derivation of PTPR and pineal parenchymal tumors, we hypothesized that expression of lineage-specific transcription factors could distinguish these tumors and provide additional insight into the differentiation of PTPR. A broad series of pineal region samples was reviewed, including 7 benign pineal glands, 4 pineal cysts, 13 pineocytomas, 28 pineal parenchymal tumors of intermediate differentiation, 11 pineoblastomas, and 18 PTPR. All samples were evaluated by immunohistochemistry for expression of CRX, a master transcriptional regulator of photoreceptor differentiation expressed in pineal gland and retina and/or FOXJ1, a master transcriptional regulator of ciliogenesis expressed in normal ependymal cells and ependymal neoplasms. Diffuse nuclear CRX expression is present in 100% of pineal samples. FOXJ1 is negative in all pineal samples. CRX staining is present in 53% of PTPR, though expression is nearly always limited to rare cells. Diffuse nuclear FOXJ1 expression is present in 100% of PTPR. Fetal human SCO diffusely expressed FOXJ1 but was negative for CRX. Immunohistochemistry for FOXJ1 and CRX differentiates non-germ cell pineal region tumors with high sensitivity and specificity, including pineal parenchymal tumors and PTPR. Our findings support the hypothesis that PTPR have ependymal differentiation and are phenotypically more similar to SCO than pineal gland.

Malignant progression to anaplastic meningioma: Neuropathology, molecular pathology, and experimental models

Meningioma is a common adult intracranial tumor, and while several cases are considered benign, a subset is malignant with biologically aggressive behavior and is refractory to current treatment strategies of combined surgery and radiotherapy. Anaplastic meningiomas are quite aggressive and correspond to a World Health Organization (WHO) Grade III tumor. This highly aggressive phenotype mandates the need for more efficacious therapies. Designing rational therapies for treatment will have its foundation in the biologic understanding of involved genes and molecular pathways in these types of tumors. Anaplastic meningiomas (WHO Grade III) can arise from malignant transformation of lower grade (WHO Grade I/II) tumors, however there is an incomplete understanding of specific genetic drivers of malignant transformation in these tumors. Here, the current understanding of anaplastic meningiomas is reviewed in the context of human neuropathologic specimens and small animal models.

Pathology and molecular genetics of meningioma: recent advances

Meningiomas are the most common intracranial primary neoplasm in adults. Although the spectrum of clinical and molecular genetic issues regarding meningiomas remains undefined, novel genetic alterations that are associated with tumor morphology, malignancy, or location have recently been discovered. This review focuses on recent advances in understanding of the heterogenous pathology of meningiomas, particularly on associations between the clinical, histological, etiological, epidemiological, and molecular genetical aspects of the neoplasm.

[Malignant meningioma with adenocarcinoma-like metaplasia: a rare entity to be not misdiagnosed]

We report on a 51-year-old woman who presented with a cervical spinal cord tumor clinically suspected to be a metastasis. Histological examination revealed an anaplastic meningioma containing epithelial nests arranged in a gland-like pattern suggestive of adenocarcinoma. This component strongly expressed cytokeratins whereas the meningothelial component was vimentin--epithelial membrane antigen--and progesterone receptor-immunoreactive, suggesting either anaplastic meningioma with adenocarcinoma-like metaplasia, or adenocarcinoma metastasis in a meningioma, but the search for a primitive neoplasia including thoracic-abdominal-pelvic computed tomography and mammography was negative. Anaplastic meningiomas with adenocarcinoma-like metaplasia are uncommon lesions, 4 cases having been reported in the literature so far. Their immunohistochemical and chromosomal characteristics are similar to those observed in secretory meningiomas. When available, fluorescence in situ hybridization detects the same chromosomal alterations in the two components, confirming a common clonal origin. This observation demonstrates the necessity to perform the correct diagnosis of malignant meningioma with adenocarcinomatous metaplasia, whose prognosis and treatment radically differ from those of metastatic adenocarcinoma located in a meningioma.

Cytopathology of extracranial ectopic and metastatic meningiomas

INTRODUCTION

Extracranial meningiomas may infrequently be encountered as ectopic or metastatic tumors. Their rarity and unique cytomorphology often pose significant diagnostic dilemmas. The aim of this study was to report our experience with a series of ectopic and metastatic meningiomas, characterizing their cytomorphology with histological correlation.

MATERIALS AND METHODS

A retrospective analysis involving 13 patients with cytological preparations from extracranial meningiomas was performed. Cytology cases were correlated with available surgical resection specimens. Data regarding clinical findings, tumor information, cytomorphology, follow-up histological features and immunohistochemistry were recorded and analyzed.

RESULTS

There were 5 cases with metastases and 8 ectopic meningiomas. Metastases occurred in the scalp/skull, lung, paraspinal soft tissue and liver. Primary ectopic meningiomas were located in the paranasal sinuses and ear, orbit and neck. Cytomorphological features characteristic of meningiomas were identified in the majority of samples including tightly cohesive clusters of spindled cells, whorls, intranuclear inclusions, nuclear grooves and psammomatous calcification. Unusual cytomorphological features identified in only a few cases included epithelioid cell predominance, abundant inflammatory cells, small-cell change, papillary structures and pseudoacinar growth. Metastatic tumors exhibited more nuclear atypia and occasionally mitoses or necrosis. Meningiomas were shown to be immunoreactive for epithelial membrane antigen, pancytokeratin and vimentin.

CONCLUSION

Although rare, extracranial meningiomas can be encountered in cytologic specimens and should be included in the differential diagnosis when characteristic morphological features of meningiomas are seen. Cytopathologists should be aware that these lesions could be mistaken for other tumors, especially when confounded by atypia and unusual cytomorphological features.

Meningeal tumors histologically mimicking meningioma

A number of meningeal neoplastic lesions may radiologically and clinically simulate meningioma. In the present paper, we review meningeal non-meningothelial tumors which may also mimic different histotypes of meningioma at the histological examination. Awareness that these lesions exist may facilitate their recognition and correct diagnosis, which is of fundamental importance for prognosis and an appropriate therapeutic approach. Histological and immunohistochemical clues for the differential diagnosis are discussed.

Immunohistochemical Detection of CD34, E-cadherin, Claudin-1, Glucose Transporter 1, Laminin, and Protein Gene Product 9.5 in 28 Canine and 8 Feline Meningiomas

The variation in histologic pattern of meningiomas can make their diagnosis challenging. The immunohistochemical profile of 28 canine and 8 feline meningiomas was examined. Tumor types included anaplastic (6 dogs), angiomatoid (1 cat), fibroblastic (3 dogs, 1 cat), meningothelial (1 dog), microcystic (2 dogs), myxoid (3 dogs), psammomatous (4 cats), and transitional (13 dogs, 2 cats). The authors compared the expression of novel markers (CD34, E-cadherin, claudin-1, glucose transporter 1 [GLUT-1], laminin, and protein gene product [PGP] 9.5) with published markers (cytokeratins, glial fibrillary acidic protein [GFAP], progesterone receptor, S100, and vimentin). Neoplastic cells were immunohistochemically positive for vimentin in 100% of the meningiomas; CD34, 94%; GLUT-1, 86%; E-cadherin, 81%; S100, 75%; laminin, 72%; claudin-1, 60%; PGP 9.5, 55%; progesterone receptor, 44%; pancytokeratins, 39%; cytokeratins 8/18, 17%, and GFAP in 9%. Ki67 index did not correlate well with mitotic index. Based on these results and those in the human literature, immunohistochemistry for vimentin, CD34, and E-cadherin is proposed to support a diagnosis of meningioma. Immunohistochemistry for claudin-1, albeit of only moderate to low sensitivity in canine and feline meningiomas, may help to distinguish meningioma from some mesenchymal neoplasms involving the brain and associated structures, such as schwannomas, which in humans express claudin-1 poorly or not at all. Further studies with CD34, E-cadherin, and claudin-1 in canine and feline tumors that may mimic meningiomas are needed to determine the adequacy of this approach.

Secretory meningiomas: a benign subgroup causing life-threatening complications

While meningiomas are known as slow-growing extracerebral neoplasms, the subgroup of secretory meningiomas with histologically benign characteristics tend to cause disproportional peritumoral edema, frequently leading to severe medical and neurological complications in postoperative management. Among 1,484 meningiomas that were resected at our institution between 1990 and 2007, 44 (3%) patients were found to have the histological diagnosis of a secretory meningioma. The clinical course, radiological appearance, and histopathological features were retrospectively analyzed to examine the specifics of these benign lesions. Meningiomas were located at the convexity (n = 14), the cranial base (18), and the sphenoid ridge (12). A severe, nearly hemispheric perifocal edema disproportional to tumor size was seen on preoperative MR imaging in 18 (41%) patients. Following surgical resection, the postoperative course was uneventful in 29 patients. In 15 patients, severe peritumoral edema continued or even increased on postoperative CT imaging. Six patients showed midline shift and clinical worsening necessitating respirator-assisted ventilation and intracranial pressure monitoring. An association between the extent of brain edema and number of periodic acid Schiff-positive pseudopsammomas was found (p < 0.02). Further, the size of the edema correlated with the number of immunohistochemically detected cells expressing carcinoembryonic antigen (CEA) and cytokeratin (CK) (p < 0.01). Mean MIB-1 (Ki-67 antigen) proliferation index was 3.0% (range, 0%-17%) and did not correlate with edema or tumor recurrence. Secretory meningiomas are frequently associated with severe peritumoral edema. The extent of edema correlates with immunohistochemically detected expression of CEA and CK. Extended perifocal edema in meningiomas is an unusual finding and should alert the neurosurgeon that surgery may aggravate edema excessively, leading to a life-threatening postoperative situation.

Immunohistochemical profiling of cytokeratin expression by endometrial stroma sarcoma

Endometrial stromal sarcomas can be confused with several neoplasms because of their inconsistent and widely varied morphologic appearance and frequent immunohistochemical expression of a variety of antigens including cytokeratin. The resulting diagnostic challenge becomes problematic particularly in the diagnosis of metastases resulting from such tumors. Because of the sometime epithelioid appearance of the tumor cells and their expression of cytokeratin, the metastases may be misdiagnosed as poorly differentiated carcinoma. We therefore studied the profile of cytokeratin proteins expression in 17 cases of endometrial stromal sarcomas using a panel of antibodies including cytokeratin cocktail antibody (AE1/AE 3), CK5/6, CK7, CK14, CK16, Cam5.2 (CK8), CK19, CK20, and 34Ebeta12 (CK1, 5, 10, and 14). Of the 17 cases, 8 (47%) stained positive with the cytokeratin cocktail antibody (AE1/AE 3). Of the 8 cases with cytokeratin expression, 5 (63%) stained positive with CK19, and 3 of them stained positive with Cam5.2. The 3 cases that stained positive with Cam5.2 also expressed CK19. Of the 5 cases with CK19, 1 was focally positive for CK5/6, CK7, and 34Ebeta12. None of the cases expressed CK14, CK16, or CK20. These results show that CK19 is most commonly expressed cytokeratin in endometrial stromal tumors. Hence, the inclusion of CK19 in the panel of immunostains may help resolve the diagnostic confusion created by keratin expression in endometrial stromal sarcoma and may also help in the correct diagnosis of endometrial stromal sarcoma at extrauterine sites.

Temporal bone secretory meningioma presenting as a middle ear mass

A 44-year-old woman presented with a history of increasing left hypoacusis and sporadic vertigo. CT scan revealed a tumor occupying the mastoid, middle ear, and external auditory canal. After surgical removal, a typical secretory meningioma was diagnosed. The histological hallmark and the immunohistochemical profile of secretory meningiomas are reviewed. The differential diagnosis of this tumor in this location is also commented on. As far as we know, primary temporal bone meningiomas with secretory histology have not been previously reported in the medical literature.

Expression of E-cadherin and catenins in meningioma: Ubiquitous expression and its irrelevance to malignancy

The expression of cell adhesion molecules in 107 meningiomas was analyzed with immunohistochemical methods using antibodies to epithelial (E)-cadherin and catenins (alpha, beta and gamma). According to the provided World Health Organization (WHO) grading, 84, 18 and five cases were classified as grade I, II and III, respectively. In addition, hemangioblastoma (15 cases) and hemangiopericytoma (four cases) were also evaluated. In most meningiomas, E-cadherin, alpha- and beta-catenins were expressed along the cell membrane or inside the cytoplasm. The tumor cells constituting whorls and glandular structures of secretory type showed a strong immunoreactivity. gamma-Catenin expression tended to be weak and infrequent in fibrous meningiomas, while other types exhibited diffuse stainings. Even in meningiomas of more than grade II, the expressions of cell adhesion molecules were detected in all cases. Hemangiopericytoma was positive for alpha- and beta-catenins, and hemangioblastomas were positive for beta-catenin alone, which was distinct from the expression pattern in meningiomas. Quantitatively, there were no correlations between the histological variants, Ki-67 indexes, or grades of meningiomas and the immunoreactive scores except for gamma-catenin scores of fibrous meningiomas. The present study demonstrates that cell adhesion molecules are ubiquitously expressed in all variants of meningioma and may be involved in the tumor morphogenesis. This result suggests that the expression of cell adhesion molecules is not a reliable indicator of malignancy in meningiomas. The present study also suggests that these markers may be useful for the differential diagnosis of meningioma.

Expression of cytokeratin by malignant meningiomas: diagnostic pitfall of cytokeratin to separate malignant meningiomas from metastatic carcinoma

Based on clinical and histologic features, differentiating metastatic carcinomas from benign or malignant meningiomas usually is not difficult. Occasionally, however, in some patients without a clinical history of carcinoma, malignant meningiomas can morphologically simulate metastatic carcinoma, necessitating an immunohistochemical study for cytokeratin to make a correct diagnosis. However, the utility of immunohistochemical markers to separate malignant meningioma from metastatic carcinoma has not been investigated. The immunoperoxidase method with antigen retrieval was used to characterize the expression of three cytokeratins (AE1/AE3, CAM 5.2, and Pan cytokeratin), EMA, CEA, Ber-EP4, CD 15, and B72.3 in 12 previously diagnosed malignant meningiomas, 20 benign meningiomas, and 20 metastatic carcinomas. Cytokeratin expression was detected in 75% of malignant meningiomas, 0% of benign meningiomas, and 100% of metastatic carcinomas. While epithelial markers of Ber-EP4, CEA, B72.3 and CD-15 were positive in 90, 80, 70 and 65% of the metastatic carcinoma, respectively, they were negative in all 12 malignant meningioma examined. Vimentin immunoreactivity was seen in all benign and malignant meningiomas, and in 20% of metastatic carcinomas. Our results indicated that cytokeratin is not a reliable immunohistochemical marker to separate a malignant meningioma from metastatic carcinoma. A panel of epithelial markers including Ber-EP4, CEA, B72.3 and CD-15, and vimentin may be needed to separate malignant meningioma from metastatic carcinoma. Cytokeratin expression can be a potential pitfall for confusing a malignant meningioma with a metastatic carcinoma.