Immunohistochemistry of central nervous system tumors. Its contributions to neurosurgical diagnosis

Reactive Astrocytes in the Morphologic Composition of Peripheral Areas of Gliomas

The participation of reactive astrocytes in the morphologic composition of peripheral areas of 25 gliomas was investigated. Reactive astrocytes were studied by the immunohistochemical demonstration of glial fibrillary acidic protein and vimentin. Reactive astrocytes were more abundant around malignant gliomas than around well-differentiated astrocytomas. They underwent modifications when entrapped within the tumor proliferation and became indistinguishable from tumor astrocytes. Mitoses occurred in both types of cells. Reactive astrocytes did participate in the cell composition of gliomas. They might have contributed to tumor growth. Practically, their occurrence might lead to an erroneous diagnosis when small fragments of tissue are examined.

Positron Emission Tomography and Computed Tomography in Differential Diagnosis between Recurrent or Residual Glioma and Treatment-Induced Brain Lesions

In previous studies of supratentorial gliomas with positron emission tomography (PET) and computed tomography (CT), high uptakes of L-methyl-11C-methionine (11C-L-methionine) were found even in astrocytomas without blood-brain barrier defects as judged by CT or 68Ga-EDTA PET. In a number of patients examined after radiation therapy, there were no consistent changes in the high uptake values. In the present investigation PET and CT were compared with regard to their abilities to visualize and delineate recurrent tumors and treatment-induced brain defects and to differentiate between them. The study was undertaken on four patients who were long-term survivors after treatment for high-grade gliomas. For PET, 11C-L-methionine and 68Ga-EDTA were used. In two patients recurrent/residual tumors appeared considerably larger with 11C-L-methionine PET than with CT or 68Ga-EDTA PET. In one patient, no signs of recurrence were seen with any of these three methods, and in a fourth patient, whose condition was clinically stable, the findings at PET with 11C-L-methionine were non-specific. In areas corresponding to the surgical parenchymal defects, the 11C-L-methionine uptake and, except in one case, the local blood volume was markedly reduced. PET with 11C-L-methionine thus has a potential for distinguishing between postoperative brain lesions and tumor recurrence with a higher accuracy than CT.

Immunohistochemical expression of glial fibrillary acidic protein and CAM5.2 in glial tumors and their role in differentiating glial tumors from metastatic tumors of central nervous system

Background and Objectives:

Immunohistochemistry (IHC) has become an important tool in the diagnosis of metastatic brain tumors. The judicious use of a panel of selected immunostains is unquestionably helpful in diagnostically challenging cases. In our study, the best combination of immune markers useful in differentiating metastatic carcinoma from high-grade gliomas in central nervous system (CNS) are glial fibrillary acidic protein (GFAP) and cytokeratin (CK) (CAM5.2).

Materials and Methods:

The study was conducted on 80 cases of glial tumors including metastatic tumors to the CNS. Histopathological diagnosis was established on routine hematoxylin and eosin staining of the sections. Special IHC markers, GFAP, and CAM5.2 were used to differentiate glial from metastatic tumors.

Result:

Of total 80 cases, 40 cases of astrocytic tumors, 2 cases of ependymoma, 2 cases of mixed glial tumors, and 16 cases of glioblastoma multiforme were positive for GFAP. Twelve cases of oligodendroglioma were negative for GFAP. The sensitivity of GFAP in glial tumors was statistically significant as 81.1% and specificity 100%, whereas sensitivity and specificity of CAM5.2 in metastatic tumors were 100%.

Conclusion:

IHC plays an important role in diagnosing tumors of CNS and markers such as GFAP and CK (CAM5.2) are quite effective in differentiating glial tumors from metastatic tumors of CNS.

Diagnosis and management challenge of a granular cell astrocytoma of the pineal region: case report

Granular cell astrocytoma (GCA) is a rare type of infiltrative brain tumor with most reported cases occurring in the suprasellar region. A pineal localization is extremely rare, with only 4 previously reported cases in the literature. The authors describe the case of a 16-year-old boy who developed signs of increased intracranial pressure and Parinaud syndrome. Cranial CT and MRI revealed a well-demarcated and enhanced mass in the pineal region accompanied by obstructive hydrocephalus. Subtotal resection was performed via a subtemporal approach. A histological diagnosis of GCA was made. Three years after surgery, the patient was alive and well without adjuvant therapy, and serial MRI showed no signs of progression of a small residual tumor. After a thorough review of the different epidemiological, clinical, and imaging features; treatments; and prognoses of GCAs in other intracranial localizations, the authors analyzed features of this tumor in the pineal region.

Multiparametric magnetic resonance in the assessment of the gender differences in a high-grade glioma rat model

Background

Glioblastoma, the most frequent and aggressive of all astrocytomas, presents a clear predominance in male humans, but the assessment of sexual differences in its tumourigenesis and growth has received little attention so far. In this study, we aim to identify gender-dependent surrogate markers in an animal model of this cancer by means of magnetic resonance (MR) imaging and biochemical and behavioural studies.

Methods

A high-grade glioma model developed in male and female rats was used. Multiparametric magnetic resonance images and localized spectra were acquired. The MR parameters linked to tumoural features were quantified. Motor and metabolic activity was also assessed. Postmortem analyses were carried out to measure indicators of malignancy, tumoural metabolism and viability of the blood-brain barrier (BBB).

Results

Statistically significant differences dependent on the animal sex were found in the study of pathological indicators like oedema, inflammation, cellularity and microvasculature. Results suggest higher cell proliferative rate, inflammation and vasogenic oedema and or necrosis in glioma-bearing male rats. Haemodynamic parameters measured indicated a major disruption of the BBB, postmortem confirmed, in this sex. Metabolomic and energetic metabolism activity data are in agreement with a major malignancy and aggressiveness of this cancer model on males.

Conclusions

Gender differences should be taken into account in preclinical studies of glioblastoma models, in the characterization of the tumoural behaviour and consequently in the development and validation of new therapeutic approaches. MR imaging and spectroscopy allow to non-invasively monitor this sexual dimorphism in the diagnosis and prognosis of brain cancer.

Subependymal giant cell astrocytoma: current concepts, management, and future directions

BACKGROUND

Subependymal giant cell astrocytoma (SEGA) is the most common central nervous system tumor in patients with tuberous sclerosis complex (TSC). SEGAs are generally benign, non-infiltrative lesions, but they can lead to intracranial hypertension, obstructive hydrocephalus, focal neurologic deficits, and even sudden death.

DISCUSSION

Surgical resection has been the standard treatment for SEGAs, and it is generally curative with complete resection. However, not all SEGAs are amenable to safe and complete resection. Gamma Knife stereotactic radiosurgery provides another treatment option as a primary or adjuvant treatment for SEGAs, but it has highly variable response effects with sporadic cases demonstrating its efficacy. Recently, biologically targeted pharmacotherapy with mammalian target of rapamycin (mTOR) inhibitors such as sirolimus and everolimus has provided a safe and efficacious treatment option for patients with SEGAs. However, SEGAs can recur few months after drug discontinuation, indicating that mTOR inhibitors may need to be continued to avoid recurrence. Further studies are needed to evaluate the advantages and adverse effects of long-term treatment with mTOR inhibitors. This review presents an overview of the current knowledge and particularly highlights the surgical and medical options of SEGAs in patients with TSC.

Antiproliferative effects of PACAP and VIP in serum-starved glioma cells

Emerging evidence have suggested that calorie restriction (CR) is a reliable method to decrease cancer development since it produces changes in tumor microenvironment that interfere with cell proliferation, tissue invasion, and formation of metastases. Studies on the role of pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) in cancer cells indicate that their influence on cell growth is either cell type specific or dependent on culture conditions. Evidence showing the effect of PACAP and VIP in glioma cells grown under conditions mimicking CR are currently unavailable. Therefore, we explored the effects of both PACAP and VIP in C6 glioma cells either grown in a normal growth medium or exposed to serum starvation, to resemble an acute condition of CR. Cell viability, expression of proteins related to cell proliferation (cyclin D1), apoptosis (Bcl2, p53, and cleaved caspase-3), and cell malignancy (GFAP and nestin) were assessed by MTT assay, immunoblot, and immunolocalization, respectively. Results demonstrated that CR significantly decreased cell proliferation, reduced levels of cyclin D1 and Bcl2, and increased the expression of p53 and cleaved caspase-3. Surprisingly, all of these CR-driven effects were further exacerbated by PACAP or VIP treatment. We also found that PACAP or VIP prevented GFAP decrease caused by CR and further reduced the expression of nestin, a prognostic marker of malignancy. In conclusion, these data demonstrate that PACAP and VIP possess antiproliferative properties against glioma cells that depend on the specific culture settings, further supporting the idea that CR might offer new avenues to improve peptide-oriented glioma cancer treatment.

Inducible expression of stem cell associated intermediate filament nestin reveals an important role in glioblastoma carcinogenesis

The intermediate filament nestin is transiently expressed in neural stem/progenitor cells during the development of central nervous system. Recently, increasing evidence has shown that upregulation of nestin is related to malignancy of several cancers, especially glioblastoma. However, the function of nestin in carcinogenesis remains unclear. In this study, we investigated the role of nestin in glioblastoma carcinogenesis by comparing subclones of rat C6 glioblastoma cells that were either high or low for nestin expression. We found that while nestin expression did not influence the in vitro proliferation of glioblastoma cells, subclones characterized by high levels of nestin formed tumors in vivo at significantly faster rates than subclones with low expression. Importantly, C6 subclones that expressed nestin at low levels in vitro were also found to give rise to tumors highly positive for the protein, suggesting that induction of nestin plays an important role in glioblastoma carcinogenesis. Derivation of nestin positive tumors from nestin negative human U87 glioblastoma cells in immunodeficient mice further confirmed that a switch to positive expression of nestin is fundamental to the course of glioblastoma development. Blocking the expression of nestin in glioblastoma tumors via intratumor injection of shRNA significantly slowed tumor growth and volume. These results demonstrated that nestin plays a crucial role in development of glioblastoma and may potentially be targeted for treatment of the disease.

Diffuse craniospinal metastases of intraventricular rhabdoid papillary meningioma with glial fibrillary acidic protein expression: a case report

Rhabdoid papillary meningioma is a recently described clinically aggressive variant of meningiomas with a high recurrence rate. Additionally, only one case of intraventricular rhabdoid meningioma has been reported so far. We present a case of a 50-year-old man who developed an intracranial tumor of the left lateral ventricle at the trigone, for which he underwent total tumor resection followed by gamma knife radiosurgery for recurrence of the tumor. The histological diagnosis was rhabdoid papillary meningioma. Five years after surgery, diffuse craniospinal leptomeningeal metastases developed and subtotal removal of the spinal tumor was performed. The spinal tumor was considered to have metastasized via cerebrospinal fluid (CSF) in view of its histological features that were identical to those of the primary tumor. Immunohistochemistry revealed the unusual cytoplasmic expression of glial fibrillary acidic protein (GFAP) of tumor cells. To our knowledge, this is the first reported case of diffuse craniospinal metastases of intraventricular rhabdoid papillary meningioma with GFAP expression and the second reported case of the rhabdoid subtype amongst intraventricular meningiomas.

Pattern of serum autoantibodies allows accurate distinction between a tumor and pathologies of the same organ

PURPOSE

Recent studies impressively showed the diagnostic potential of seroreactivity patterns for different tumor types, offering the prospect for low-cost screening of numerous tumor types simultaneously. One of the major challenges toward this goal is to prove that seroreactivity profiles do not only allow for identifying a tumor but also allow for distinguishing tumors from other pathologies of the same organ.

EXPERIMENTAL DESIGN

We chose glioma as a model system and tested 325 sera (88 glioma, 95 intracranial tumors, 60 other brain pathologies, and 82 healthy controls) for seroreactivity on a panel of 35 antigens.

RESULTS

We were able to discriminate between glioma and all other sera with cross-validated specificity of 86.1%, sensitivity of 85.2%, and accuracy of 85.8%. We obtained comparably good results for the separation of glioma versus nontumor brain pathologies and glioma versus other intracranial tumors.

CONCLUSION

Our study provides first evidence that seroreactivity patterns allow for an accurate discrimination between a tumor and pathologies of the same organ even between different tumor types of the same organ.

Lucien J. Rubinstein: enduring contributions to neuro-oncology

Dr. Lucien Rubinstein is best remembered for his significant contributions to the field of neuropathology, particularly in the classification of nervous system tumors. His accomplishments in basic neuro-oncology and in the formulation of diagnostic principles reflected a unique talent for synthesizing fundamental clinicopathological concepts based on skillful diagnostic investigation and a thorough understanding of neurobiology. Dr. Rubinstein was the leader in the establishment of cell cultures from central nervous system (CNS) tumors. He meticulously analyzed both light and electron microscopic features of CNS tumors, recorded his findings, and patiently drew sketches to be shared generously with his colleagues and students. As a pioneer in neuropathology, in his work Dr. Rubinstein set the foundation for many enduring concepts in neurosurgery, neuro-oncology, neurology, and basic tumor biology.

Primary rhabdomyosarcoma associated with tumoral hemorrhage--case report

A 42-year-old female presented with right hemiparesis. Computed tomography (CT) demonstrated a slightly heterogeneous high density mass over the left frontal convexity with peritumoral edema, with homogeneous enhancement by contrast material. Magnetic resonance imaging showed the left frontal convexity tumor as a heterogeneous low intensity area on the T1-weighted image and a heterogeneous high intensity area on the T2-weighted image, with homogeneous enhancement and dural tail sign after intravenous administration of gadolinium-diethylenetriaminepenta-acetic acid. After admission, the patient suddenly lost consciousness. CT demonstrated aggressive increase in the bulk of the tumor and large peritumoral hemorrhage. The tumor was totally removed. The histological diagnosis was rhabdomyosarcoma. Combined immunohistochemistry and electron microscopy techniques should be used to differentiate rhabdomyosarcoma from malignant meningioma.

Atypical pleomorphic astrocytoma in the pineal gland: case report

OBJECTIVE AND IMPORTANCE

We report a rare case of pleomorphic astrocytoma in the pineal region that took a benign course despite pleomorphism.

CLINICAL PRESENTATION

A 30-year-old woman suddenly developed right hemiparesis followed by loss of consciousness. A computed tomographic scan revealed a mass in the pineal region accompanied by obstructive hydrocephalus. Her symptoms improved after ventriculoperitoneal shunt surgery.

INTERVENTION

The tumor was totally removed in an en bloc fashion using the occipital interhemispheric transtentorial route. Light microscopy revealed that the tumor had marked pleomorphism and multinucleated, bizarre giant cells, but neither mitosis nor necrosis was seen. Glial fibrillary acid protein was immunohistochemically positive in a few tumor cells. Retinal soluble antigen was negative. No reticulin network between the tumor cells was observed. A histological diagnosis of atypical pleomorphic astrocytoma was made.

CONCLUSION

No signs of recurrence have been observed for 7 years after surgery without adjuvant therapy. Histologically, the tumor resembled pleomorphic xanthoastrocytoma or pleomorphic granular cell astrocytoma, but the immunohistochemical findings were not completely compatible with either diagnosis. This benign astrocytoma in the pineal gland with unique features is the first such case reported.

Immunohistochemical characterization of hepatoblastomas in B6C3F1 mice treated with diethylnitrosamine and sodium phenobarbital

Hepatoblastomas (HBs) were induced in B6C3F1 male mice by diethylnitrosamine (DEN) and sodium phenobarbital (PB). Six-week-old mice received a single intraperitoneal dose of DEN followed by a continuous treatment with PB in diet at a concentration of 0 (group 1) or 500 (group 2) ppm for 50 weeks. HBs were observed in 13 of 21 (62%) group 2 mice, with typical histologic features as reported previously, while no such tumors were observed in group 1. Seven of 13 (54%) HBs were found in and/or adjacent to hepatocellular adenomas (HCAs) or hepatocellular carcinomas (HCCs). Immunohistochemically, all HBs were positive for S-100 protein but negative for keratin, alpha-fetoprotein (AFP), albumin (ALB) and vimentin, while HCC cells occasionally reacted positively for AFP with a mosaic pattern. HCC and HCA cells were occasionally positive for ALB. Non-neoplastic hepatocytes and normal bile ducts were positively stained for ALB and keratin/S-100 protein, respectively. S-100 protein is known to be expressed in many mesenchymal tissues and neoplasms including neuroectodermal elements but negative in cells of the hepatic lineage. Thus, the present immunohistochemical results suggested that mesenchymal differentiation occurs in mouse HB cells as observed in human HBs, one of the most frequent infant liver tumors in humans. Although the susceptibility of mouse HBs to PB-promotion suggests a hepatocytic histogenesis, the present immunohistochemical results support the hypothesis that the mouse HB is derived from pluripotent endodermal stem-like cells.

Neuroendocrine, immunohistochemical, and ultrastructural study of pineal region tumors

Thirteen patients with tumors in the pineal region were submitted to pre- and post-operative blood sampling (08:00, 14:00, 20:00, and 02:00 hr) for three or four consecutive days. A single cerebrospinal fluid (CSF) sample was collected at surgery, and melatonin levels determined. In all patients, serum and CSF beta subunit of human chorionic gonadotrophin (betaHCG), carcino embryonic antigen (CEA), and alpha-fetoprotein (AFP) levels were measured. Histology revealed four pineocytomas, one pineoblastoma, four germinomas, one immature teratoma, one pilocytic astrocytoma, one lymphoma, and one meningioma. Serum and CSF levels of serological biomarkers were normal, except for one of the germinoma cases. In most patients, alteration either in the circadian rhythm or in the melatonin concentration was observed before surgery. In benign neoplasms the circadian rhythm was conserved. In pineoblastoma, lymphoma, and three out of four germinomas, melatonin concentrations were undetectable. In one case of germinoma, melatonin levels were high, with the circadian rhythm being abolished. According to conventional histology, all germinomas were similar. Therefore, in a rare case of pineal germinoma with high melatonin levels, the tissue was subjected to an in depth investigation (immunohistochemical and ultrastructural) in order to determine the pathology and the possible differences from the other typical germinomas. Results were compared to those provided from other pineal neoplasms. Electron microscopy examination detected the presence of clusters of intermediate filaments and numerous electrondense granules only in the case of a germinoma producing melatonin.

Molecular characterization of glioblastoma cell differentiation

OBJECTIVE

Induction of cellular differentiation continues to be an attractive therapeutic strategy for malignant glioma. The purpose of this study was to develop a convenient in vitro model system for glioblastoma differentiation and to then characterize it using conventional techniques and flow cytometry.

METHODS

A subline of U138 MG cells ("U138B") was treated with 0 to 4 mmol/L sodium butyrate (or serum deprivation) for up to 96 hours. Cells were initially studied for effects on proliferation, morphology, and glial fibrillary acidic protein (GFAP) staining. Northern blot and immunoblot analyses of c-myc expression were performed. Multiparameter flow cytometry was then used to analyze GFAP, c-myc protein, and total cellular protein fluorescence and to relate them to changes in cell cycle distribution.

RESULTS

Butyrate treatment produced a dose-dependent inhibition of cellular proliferation and changes in morphology, GFAP staining, and c-myc expression consistent with a differentiation response. Detailed flow cytometric studies, including subpopulation analysis, showed that during 72 hours of treatment with 2 mmol/L butyrate, mean GFAP fluorescence increased to 420%, whereas c-myc protein decreased to 45 +/- 13% and total cellular protein increased to 181 +/- 17%. The effects of butyrate were distinct from those of serum deprivation and were not simply the result of cells shifting into Gzero/G1.

CONCLUSION

The butyrate-induced responses of the U138B cell line provide a convenient model system for studying the molecular events accompanying the differentiation of glioblastoma cells. Multiparameter flow cytometry is a useful technique for characterizing such differentiation.

A malignant astrocytoma containing simian virus 40 DNA in a macaque infected with simian immunodeficiency virus

Polyomaviruses have proven oncogenicity in nonhost experimental animals; however, studies concerning the association between human brain tumors and simian and human polyomaviruses have yielded inconclusive results. We examined the relationship of SV40 to a malignant astrocytoma found in the right frontal lobe of a pigtail macaque (Macaca nemestrina) infected with simian immunodeficiency virus (SIV). Consistent with the histologic diagnosis, the tumor was immunoreactive with antibodies to S-100 protein, vimentin, and glial fibrillary acidic protein, but negative for neurofilament protein, synaptophysin, neuron-specific enolase, and chromogranin A. At the time of SIV inoculation, the animal was seropositive for SV40. Polymerase chain reaction assay of tumor DNA, but not normal brain DNA, yielded a 300 base-pair fragment corresponding to the carboxy-terminal coding region (C-terminus) of the large T antigen gene of SV40, suggesting an association with the tumor.

Dynamic characterization of glioblastoma cell motility

The cell motility dynamic of two glioblastoma cell lines (U373 and U87) was studied by means of an automatic video-cell-tracking-system enabling each cell in a colony to be tracked for several hours. Twenty-five experiments were performed on both models growing on three different supports (glass, plastic and Matrigel). Cell motility was significantly different in each cell line and also for different growth support in a given cell line. We observed that U87 cells are significantly (p < 0.00001) less motile than U373 cells. The most favorable growth supports for cell motility studies were Matrigel and glass. A significant (p < 0.001) correlation between cell colony density and cell motility was highlighted, with isolated cells exhibiting a motility level distinct from the one observed for colonies. The present methodology, which enabled cell motility to be quantified in human glioblastoma cells, represents an original tool for identifying new classes of compounds able to reduce glioblastoma cell motility and cell migration potential into the brain.

Immunohistochemistry in diagnostic dermatopathology

Immunopathology continues to be important in diagnostic dermatopathology. Immunopathology is an invaluable tool for assessing the tissue of origin or direction of differentiation of cells. In some cases this can result in a more precise diagnosis. This article reviews the role of immunopathology in determining the biologic behavior of hematolymphoid infiltrates. It explores the methodology of immunoperoxidase, discusses the most commonly used antibody reagents, and presents a series of diagnostic dilemmas in which immunopathology can be useful. In each case a strategy is established that maximizes the likelihood of making a definitive diagnosis.

Tumor antigens in astrocytic gliomas

Gliomas affect 15,000 to 17,000 Americans every year and carry a dismal prognosis. The potential of immunologically mediated diagnosis and therapy, although greatly enhanced since the advent of monoclonal antibodies, has not been fully realized due to significant problems, most especially the challenge of identifying antigenic molecules specific to glial tumors. Other problematic issues include antigen-associated factors such as heterogeneity, modulation, shedding, and cross-reactivity with normal cells, and factors associated with therapeutic agent delivery, typically variable tumor perfusion and unfavorable diffusional forces in tumor microenvironment. An understanding of these problems called for the delineation of operationally specific antigens (tumor-associated antigens not expressed by the normal central nervous system) combined with the use of compartmental therapeutic approaches to increase the specificity of therapy. Numerous antigens have been identified and are classified as extracellular/matrix-associated, membrane-associated, and intracellular antigens. Nevertheless, only a few have been demonstrated to be of significant therapeutic and diagnostic utility. These few include the extracellular matrix-associated antigens tenascin and GP 240, defined by the monoclonal antibodies 81C6 and Mel-14, both of which are now in Phase I clinical trials, and membrane-associated ganglioside molecules, primarily 3', 6'-isoLD1, defined by the antibody DMAb-22. Recent identification of the overexpression of a deletion variant of the epidermal growth factor receptor (EGFRvIII) in up to 50% of the more malignant glial tumors and the subsequent creation of monoclonal antibodies that are specific to this molecule and do not recognize the wild-type EGFR provide the most exciting development yet in the design of specific antiglioma immunoconjugates. In addition, the tumor-specific nature of EGFRvIII combined with improved knowledge of immune mechanisms, especially in the context of the central nervous system, will facilitate the design of highly selective cell-mediated therapeutic approaches with a view toward obtaining tumor-specific immunity.

Immunohistochemical characterization of 'small, lymphoid-like cell populations' within germinomas: immunologic and molecular approaches to diagnosis

Little is known to date about the biological and molecular characteristics of 'small lymphoid cells' within intracranial germinomas. Frozen sections from three germinoma specimens were evaluated immunohistochemically in order to identify phenotypic markers expressed on human lymphoid cells as well as intercellular adhesion molecules. In addition, T-cell receptor (TCR) variable alpha- and beta-chain mRNA expression was analyzed by polymerase chain reaction (PCR). The small cells stained faintly with anti-CD5 in two specimens, but were negative for the T cell specific markers, CD2, CD3, CD7, and CD8. In addition, these cells were weakly positive for CD11b (Mac-1) and CD54 (ICAM-1), but were negative for lymphocyte-specific CD11a (LFA-1) and CD11c (p150,95). No TCR V alpha or V beta gene expression was detected by PCR within these germinoma specimens. The small cells of germinomas with the cytologic appearance of lymphocytes are not derived from T-cells or other lymphocytic lineages.

Low-grade astrocytomas may arise from different astrocyte lineages

The management of low-grade astrocytomas remains a challenge. Although the majority of these tumors have common histological features, they may have very different clinical manifestations and rates of proliferation. Because low-grade astrocytomas are composed of relatively well-differentiated neoplastic cells that closely resemble the astrocytic phenotype, it is possible that some of these lesions express antigens that characterize astrocyte lineages. The authors performed an immunohistochemical analysis of 20 low-grade astrocytomas with A2B5, a monoclonal antibody to a ganglioside found in early postnatal Type 2 (fibrillary) astrocytes, but absent in Type 1 (protoplasmic) astrocytes, and anti-glial fibrillary acidic protein to determine whether the expression of these antigens could be used to determine the histogenesis of these tumors. These findings were compared with the clinical and imaging features of these tumors. The percentages of cells positive for A2B5 and glial fibrillary acidic protein was strongly correlated with the location of the tumor within the cortex or white matter and with the length of preoperative symptoms. Tumors based in the cortex contained significantly fewer A2B5-positive and glial fibrillary acidic protein-positive cells than white matter tumors. In addition, lesions that caused a relatively short period of preoperative symptoms (< 1 year) had significantly more A2B5-positive and glial fibrillary acidic protein-positive cells than lesions responsible for a long preoperative history (mean, 12.9 years). These findings suggest that slow-growing, cortically based low-grade astrocytomas have a phenotype consistent with the Type 1 (protoplasmic) astrocyte lineage, while white matter low-grade astrocytomas express antigens consistent with the Type 2 (fibrillary) astrocyte lineage.

Immunohistochemical and ultrastructural investigation of granular cell tumours in dog, cat, and horse

Six canine, one feline and one equine granular cell tumours (GCTs) were investigated electron microscopically and immunohistochemically. The tumours were tested for reactivity with monoclonal antibodies against vimentin and desmin and with polyclonal antibodies against cytokeratin, S-100 protein, glial fibrillary acidic protein (GFAP) and neuron specific enolase (NSE). All GCTs were characterized by their PAS positive cytoplasmic granules in light microscopy, which in electron microscopy appeared as lysosome-like granules. In each case two canine GCTs were stained by the antibody against cytokeratin, vimentin and S-100 protein. Cells of the equine GCT showed reactivity with the antiserum against S-100 protein. In the feline GCT no reactivity with any of the antibodies tested was observed. These differences of the immunohistochemical reactions of GCTs suggest a nonuniform histogenesis of GCTs in domestic animals. The reactivity of the tumour cells with the antiserum against NSE is discussed.

Inflammatory leukocytes associated with increased immunosuppression by glioblastoma

In order to determine the in vivo immune response in glioblastoma, monoclonal and polyclonal antibodies specific for inflammatory leukocytes and immunoregulatory products were utilized to stain tissue from four surgical specimens. The more activated the inflammatory cells, the more activated the tumors appeared to be. In the tumor with the largest infiltration (Case 3), inflammatory cells were stained for interferon-gamma, interleukin-2, interleukin-1 beta, lymphotoxin, tumor necrosis factor-alpha, and transforming growth factor-beta. The tumor cells also expressed interleukin-1 beta, interleukin-6, transforming growth factor-beta, tumor necrosis factor-alpha, and prostaglandin E. In contrast, in the tumor with the least inflammatory response (Case 1), the tumor cells did not express any cytokines. Expression of cytokines by glioma cells was modest in the two cases with modest inflammatory responses. Cellular inflammation, primarily consisting of T cells and macrophages with few or no B cells or natural killer cells, was two- to 15-fold greater outside the tumor than within. In contrast to leukocytes outside the tumor, which were activated and expressing class II major histocompatibility antigens, leukocytes within the tumor parenchyma or at the tumor's edge were negative for these antigens. In the four specimens studied here, the tumor cells themselves were also negative for class II major histocompatibility antigens. These findings, although preliminary, suggest that inflammatory cells within gliomas are inactivated and that glioma cells may increase the expression of immunosuppressive cytokines in response to an increased lymphocyte infiltrate. This observation, if corroborated by more extensive studies, may help to explain the failure of immune treatments in glioblastoma multiforme.

Biology and treatment of gliomas

This review discusses some of the recent advances in glioma research and treatment. Our understanding of the characteristics of these tumors has been strengthened by the application of molecular biologic and genetic techniques to pathologic grading and therapy outcome. Newer attempts to correlate imaging modalities to pathologic grading are also discussed. It is anticipated that these developments will strengthen our ability to design improved treatment strategies, an essential goal inasmuch as current treatment schemes have limited benefit. More work needs to be done to understand the biology of these tumors especially the complex interactions of their cytokine expression, multiplicity of genetic abnormalities, and their local environment. Only then will be able to develop improved therapeutic interventions.

Establishment of a new cell line derived from a human gliosarcoma

A permanent cell line, GI-1, was established from a human gliosarcoma, and its characteristics were investigated. The original tumor was a mixture of two different neoplasms which had components of both glioma and sarcoma. The established cell line expressed various mesenchymal antigens, but not neuroepithelial antigens. It was noted, however, that the cell line produced tumors with the morphological features of human glioma after inoculation in athymic mice. The contrast of the pathological characteristics in tissue culture and in xenograft was unique, and this finding suggests that the GI-1 cell line may have the features of both glioma and sarcoma.

Melanoma-associated antigens in tumours of the nervous system: an immunohistochemical study with the monoclonal antibody HMB-45

The aim of this study was to determine the specificity and sensitivity of the commercially available, monoclonal anti-melanoma antibody HMB-45 in brain tumours and peripheral nerve sheath tumours. Hence, a series of 155 different non-melanotic tumours of the central and peripheral nervous system were examined immunohistochemically. The brain lesions consisted of primary tumours and metastases from various carcinomas. Twenty melanotic tumours (cerebral metastases of malignant melanomas, meningeal melanomatosis, meningeal melanocytomas) and dermal blue cell naevi served as controls. All melanotic tumours stained positive. Furthermore, a positive immunohistochemical reaction was observed in the following non-melanotic tumours: gliosarcomas, primitive neuroectodermal tumours, ependymoma, malignant schwannomas and different intracranial hamartomas. Two plasmacytomas and 4 metastatic carcinomas also revealed positive staining for HMB-45. Our results confirm the necessity for cautious interpretation of HMB-45 immunoreactivity as a tool in the immunohistochemical characterization of nervous system tumours.

A continuous cell line (KK-2) from a supratentorial primitive neuroectodermal tumor

Tumor tissue located in the occipital lobe with hemorrhage was obtained from a 19-year-old patient. Histological examination indicated it to consist of undifferentiated small, round cells without neuronal or glial differentiation, and possibly to be a type of primitive neuroectodermal tumor. The tumor cells were cultured for 3 years and a continuous cell line (KK-2) was established. KK-2 was transplantable to nude mice. With immunocytochemistry, neuron-specific enolase, protein gene product 9.5, vimentin, TUJ1 (a monoclonal antibody specific for neuron-associated class III beta-tubulin isotype) and 6H7 (a monoclonal antibody to NCAM produced by us) were detected. None of the following could be found: glial fibrillary acidic protein, S-100 protein, neurofilament and synaptophysin, calcitonin gene-related peptide, gastrin releasing peptide corticotropin-releasing factor, substance P, somatostatin, chromogranin, aromatic L-amino acid decarboxylase and tyrosine hydroxylase. The original tumor and KK-2 cells obtained after 3 years of culture and transplants in nude mice displayed essentially the same ultrastructural and immunohistochemical characteristics. KK-2 cells showed no differentiation to mature neuronal, glial or ependymal cells. This cell line may possibly serve as a useful model for studying cellular differentiation of human neuroectodermal tumors and normal neuronal development.

Paragangliomas of the head and neck. Immunohistochemical analysis of 16 cases in comparison with neuro-endocrine carcinomas

Sixteen cases of paragangliomas of the head and neck including 8 of the vagal body, 3 of the carotid body, 2 jugulotympanic, 2 vagal or jugulotympanic and 1 of the larynx were analysed. Clinically, 13 tumors were benign, 2 showed local aggressivity and 1 showed metastases. All tumors were tested with antisera directed against neuron-specific enolase (NSE), chromogranin A (CGA), S-100 protein, neurofilaments (NF), glial fibrillary acid protein (GFAP) and cytokeratin (CK). Immunohistochemical results were compared with those of 5 cases of neuroendocrine carcinoma (NC) (1 of the oral vestibule, 1 of the larynx, 1 Merkel-cell tumor of the skin and 2 medullary thyroid carcinomas). Immunoreactivity for NSE and/or CGA was always positive in all paragangliomas and NC. S-100 protein was positive in sustenticular cells in all cases of paragangliomas and focally in two cases of NC. NF and GFAP were focally positive in 3 and 2 paragangliomas respectively; and in 1 NC. CK was constantly negative in all cases of paraganglioma and constantly positive in all cases of NC. Antibody anti-CK is the single most useful immunomarker for differential diagnosis between paraganglioma, frequently benign neoplasms and NC commonly aggressive in the head and neck. These findings are consistent with the current concepts of the neuroendocrine system.

Primary angiosarcoma of the central nervous system. Study of eight cases and review of the literature

Angiosarcoma arising in the central or peripheral nervous system has rarely been reported. Eight patients with primary angiosarcoma of the central nervous system are described here; these included five males and three females ranging in age from 2 weeks to 72 years (mean 38 years). Of the eight neoplasms, six were located in the cerebral hemispheres and one was in the meninges; the site was unknown in the other. All patients underwent surgical resection. Five of the eight patients died, four within 4 months after surgery and one after 30 months. Two of the remaining three patients were 17 and 27 years old at the time of diagnosis and were alive at follow-up review 39 and 102 months after surgery, respectively. One patient was lost to follow-up monitoring. Microscopically, all eight tumors demonstrated a well-differentiated pattern with irregular vascular channels and intraluminal papillae; in addition, four showed poorly differentiated solid areas. Immunohistochemical staining of neoplastic cells to factor VIII-related antigen and Ulex europaeus agglutinin I was performed in five tumors and was focally positive in four. No correlation could be shown between the histological features and the growth and biological behavior of the tumors.

Prognostic implications of glial fibrillary acidic protein containing cell types in oligodendrogliomas

In oligodendroglial tumors the intermediate filament glial fibrillary acidic protein (GFAP) may be expressed by cells with the morphologic characteristics of typical oligodendrocytes (gliofibrillary oligodendrocytes [GFOC]) and by miniature forms of gemistocytes (minigemistocytes) as well. These latter cell types have been regarded as transitional cells that represent intermediate forms between an oligodendroglial and an astrocytic phenotype. Furthermore, in oligodendrogliomas GFAP may be expressed by intermingled classic large gemistocytes, which are not considered transitional cells. In a retrospective study of 111 oligodendrogliomas, the presence of the various GFAP-positive cell types was correlated with the survival rates of the patients. Therefore, GFAP expression was visualized with the use of an indirect conjugated peroxidase method. The survival times of the patients were recorded and statistical comparisons were made. The percentage of GFAP-positive tumor cells is increased in oligodendrogliomas of 28 patients who underwent a second biopsy (all these patients had been treated with radiation therapy as well). It was found that neither the presence of GFOC nor that of minigemistocytes is predictive of the survival. In contrast, patients with classic gemistocytes had survival lengths approximately twice as short as those of patients who did not have these cells in their tumors. No clear correlation was found between tumor grading or any of the individual histopathologic features with the presence of the various GFAP-positive cell types. The ominous sign of the presence of gemistocytes in oligodendrogliomas confirms some earlier reports about the prognostic significance of this cell type in astrocytomas.

Brain tumours in south Brazil: a retrospective study of 438 cases

All brain tumours diagnosed since 1967 in a University Hospital in the Southern region of Brazil were reviewed and clinical information concerning age, sex, symptoms and evolution were analysed. 88.1% of tumours were primary neoplasms and the rest secondary deposits. There was a male predominance and the second and fifth decades of life were the most affected. The main presenting symptoms were headache, vomiting, hemiparesis, loss of vision and epilepsy. The commonest tumour was of astrocytic origin (36.3%) amongst which the malignant ones, including glioblastoma multiforme, predominated. These tumours were frequent in the cerebral hemispheres (31.3%), particularly in the frontal lobes. The time of evolution from the beginning of the clinical manifestations until the first hospital admission was also studied. The authors discuss the clinical and pathological observations in relation to other large series analysed in the literature.

Neurofilament and chromogranin expression in normal and neoplastic neuroendocrine cells of the human gastrointestinal tract and pancreas

To differentiate neuroendocrine (NE) neoplasms arising at different levels of the gut and pancreas, the authors studied the expression of neurofilament (NF) proteins and chromogranin (CR) in normal and neoplastic NE cells of the human gastrointestinal tract (GIT) (14 ileal/jejunal carcinoids, six appendiceal carcinoids, 11 rectal carcinoids) and pancreas (23 islet cell tumors). Among pancreatic islet cell tumors, those with middle molecular weight (NF-M)-positive cells were more abundant than those with high molecular weight (NF-H)-positive cells; nearly all of these tumors expressed CR. Although NF-M was abundantly expressed in greater than 50% of tumor cells in a subset of these tumors, only one of these tumors exhibited diffuse immunoreactivity with NF-H. Among rectal carcinoid tumors, NF-M and NF-H-positive cells were present in approximately the same number of tumors, yet only diffuse immunoreactivity to NF-H could be detected. Chromogranin immunoreactivity in greater than 50% of tumor cells was present in 74% of islet cell tumors, 93% of ileojejunal carcinoids, and 83% of appendiceal carcinoids, but only in a minority of rectal carcinoids (36%). Although ileojejunal carcinoid tumors rarely expressed NF-M and did not express NF-H, diffuse immunoreactivity with CR was present in nearly all of these tumors. None of the appendiceal carcinoid tumors expressed NF-M or NF-H, yet all of these tumors demonstrated immunoreactivity with CR. Neurofilament immunoreactivity was not detected in normal GIT and pancreatic NE cells, whereas CR immunoreactivity was always present. These results suggest that for NE neoplasms of the GIT and pancreas the differential expression of NF subtypes appears to be related to tumor site; and CR is a marker of most GIT and pancreatic NE neoplasms although NF may discriminate subtypes of GIT and pancreatic NE tumors. Neurofilament subtyping may be useful in the evaluation of the origin of NE tumors presenting as metastatic lesions.

Contrary effect of lactic acid on expression of neuron-specific enolase and glial fibrillary acidic protein in human glioma cells

We examined the effect of lactic acid on cultured human glioma cell lines expressing glial fibrillary acidic protein (GFAP), vimentin and neuron-specific enolase (NSE). The growth of the cells was inhibited by the lactic acid in a dose-dependent manner. At 56 mM of lactic acid, the surviving cells of the KNS-42-c2 cell line developed slender processes and increasingly formed bizzar giant cells. In an immunofluorescence study of the lactic acid-resistant cells, the GFAP-positive cells prominently decreased in number, while the NSE-positive cells clearly increased. The vimentin was not affected throughout the experiment. After removing lactic acid from the medium, the GFAP-positive cells gradually increased in number. The method of dot immunoassay was useful for quantifying GFAP in cellular extracts. It indicated that the amount of GFAP decreased in the cells cultured with lactate-containing media and increased to the primary values after removing the lactic acid. These results may suggest that the morphological and immunochemical diversities of glioma cells are secondarily affected by cellular microenvironments such as lactic acid.

Dibutyryl cyclic AMP induces vimentin and GFAP expression in cultured medulloblastoma cells

Evidence for the astrocytic lineage in medulloblastomas rests largely on the detection of the glial fibrillary acidic protein (GFAP) from which intermediate filaments (IF) specific for astrocytes are assembled. Astrocyte progenitor cells from the mouse neopallium however express another IF protein, vimentin, before they acquire GFAP in vivo and in vitro. The purpose of the current study was to determine if cells obtained from a focally GFAP-positive posterior fossa medulloblastoma previously shown to acquire GFAP in response to dibutyryl cyclic AMP (dBcAMP), also express vimentin before expressing GFAP. More than 80% of cells in the tumor section contained vimentin while fewer than 1% of cells contained GFAP; occasional clusters of malignant GFAP-positive cells and clusters of cells negative for both vimentin and GFAP were also identified in the tumor. One hundred per cent of cultured cells in the first 10 passages from the tumor contained vimentin and no cells expressed GFAP. When cells were cultured in the presence of dBcAMP. Western immunoblotting showed an increase in vimentin which reached maximal values within 24 h followed by an increase in GFAP which reached maximal values at 72 h. The increase in vimentin followed by that of GFAP in cultured medulloblastoma cells has not previously been reported and suggests that most astrocyte progenitors which are derived from medulloblastoma and cultured in vitro may be at a developmental stage which corresponds to the proastroblast stage in the developing mouse brain.(ABSTRACT TRUNCATED AT 250 WORDS)

An immunocytochemical comparison of glial fibrillary acidic protein, S-100p and vimentin in human glial tumors

Immunostaining patterns of glial fibrillary acidic protein (GFAP), S-100 protein (S-100p) and vimentin were studied using immunohistochemical techniques on 48 paraffin embedded glial tumors. GFAP was positive in all tumor cases except in two oligodendrogliomas. S-100p was found in most astroglial tumors and in half of the oligodendrogliomas. Vimentin was positive in many astrocytomas but in no oligodendrogliomas. Most astroglial tumors showed similar immunoreactivity for GFAP and S-100p. Fibrillary processes, however, showed stronger and more crisp staining with anti-GFAP than with anti-S-100p, whereas cell nuclei were labeled only for S-100p. Vimentin was localised mainly in juxtanuclear positions. In many astrocytomas with different degrees of malignancy co-expression of GFAP, S-100p and vimentin was found. The presence of GFAP and S-100p was not correlated with the degree of differentiation in astrocytomas. Vimentin was more positive in anaplastic astrocytomas but this finding was not statistically significant. It seems that GFAP is a superior marker to S-100p and vimentin in the identification of human gliomas.

"Anemone" cell (villiform) tumor of the brain

At age 31, the patient developed hydrocephalus secondary to a brain lesion that had been present for 12 years. A ventriculoperitoneal shunt was performed, but a stereotactic biopsy did not establish a definitive diagnosis at that time. At age 34 the patient experienced spontaneous intratumoral and ventricular hemorrhage, which prompted radical surgical resection of the lesion. Histologic and immunocytochemical findings established a diagnosis of ependymoma; review of the ultrastructure of the tumor from the biopsy performed when the patient was 31 years old revealed the characteristics of an "anemone" cell neoplasm.

Immunohistochemical characterization of rat central and peripheral nerve tumors induced by ethylnitrosourea

Ethylnitrosourea-induced central and peripheral nerve tumors in Sprague-Dawley rats were tested for GFAP (Glial Fibrillary Acidic Protein), S-100 protein, NSE (Neuron Specific Enolase) and Anti-Leu 7 (HNK-1) immunoreactivity utilizing the ABC method (avidin-biotin-complex) for GFAP, S-100 protein and NSE, and the PAP method (peroxidase-antiperoxidase) for Anti-Leu 7. Peripheral nerve neurinomas were consistently positive for S-100 protein and consistently negative for GFAP and Anti-Leu 7. Neurinomas would occasionally exhibit positive staining for NSE (2 of 55 tumors). The staining intensity for S-100 protein varied from strongly positive in differentiated neurinomas to weakly positive in anaplastic tumors. Neoplastic and reactive astrocytes exhibited positive staining for both S-100 protein and GFAP. Variation in the GFAP staining intensity of glial tumors correlated with the degree of differentiation as anaplastic tumors did not stain with the same intensity as their more differentiated counterparts. Oligodendrogliomas exhibited occasional immunoreactivity to S-100 protein (3 of 36 tumors). NSE reactivity in oligodendrogliomas was rarely observed (1 tumor in 36) and immunoreactivity against GFAP or Anti-Leu 7 was consistently absent. Anti-Leu 7 and NSE proved to be of little value in the classification of ENU-induced neural tumors.

Immunobiology of brain tumors

In summary, many actual interactions between tumors in the CNS and the immune system have been demonstrated. The normal brain does not possess a lymphatic system and is partially hidden from the systemic immune system by the BBB, furthermore brain cells do not express MHC antigens which are necessary for the initiation of an immune response. In pathological conditions however, immunocompetent cells may find their way through transformed endothelial cells. Microglia and astrocytes may function as antigen presenting cells. Glioma cells when stimulated by cytokines such as IFN gamma can be induced to express MHC class I and class II antigens, thus making them more susceptible to an immune attack. In addition glioma cells are capable of secreting several cytokines including IL 1, IL 3 and IL 6 also involved in the generation of an immune response. Indeed, a functional analysis of lymphocytes infiltrating gliomas has revealed the accumulation at the tumor site of cytotoxic T lymphocytes as well as NK cells. However host-immune responses against gliomas seem to be weak in comparison to other cancers. Glioma cells are known to secrete TGF beta 2 and PGE 2 which may in part be responsible for this lack of immune response, thus shielding themselves from immune attack. In order to be recognized by the immune system the tumor cells must express TAA in addition to MHC antigens, and such TAA have been identified by MAbs. These MAbs can be used for "targeted" therapy when coupled to toxic agents or radionuclides. Preclinical studies have shown that, after intravenous or intracarotid injection, there is specific accumulation of the MAb in the tumor but in insufficient amounts for therapeutic use. The relatively small amount of MAb binding to the tumor in vivo can be due to several factors: not all the cells in a single tumor express a given tumor-associated antigens, the MAb may have a low affinity for the antigen, the BBB may hinder the passage of the MAb. Attempts have been made to overcome these drawbacks by opening the BBB for example. In addition MAbs can readily be used for the treatment of carcinomatous meningitis. There has been little success in the development of immunotherapy with IFN beta 1 and even less with adoptive immunotherapy using LAK cells plus IL 2. TIL as well as LAK cells can be expanded in vitro with IL2 and it is feasible to reinject these cells into the tumor site.(ABSTRACT TRUNCATED AT 400 WORDS)

Histogenesis and cell lineage analysis of medulloblastomas

Although the histopathology, ultrastructural features, and cellular immunoreactivity for neuron-specific enolase and synaptophysin suggest that medulloblastomas are neuronal in character, the histogenesis of these tumors has not been firmly established due to conflicting observations surrounding the expression of intermediate filament proteins. In the present study the question of cell lineage in medulloblastomas was re-explored by examining tumors for the presence of neurofilament protein using a highly sensitive assay which employs a cocktail of monoclonal antibodies, as well as A2B5 antigen, and glial fibrillary acidic protein. With this assay, 12 of 14 tumors tested (86%) expressed high levels of both neurofilament protein and A2B5 antigen, whereas glial fibrillary acidic protein was either absent or expressed in very low percentages of the cells. The distributions of neurofilament and A2B5 antigens closely paralleled one another. These observations suggest that medulloblastomas have a common histogenesis from A2B5+ progenitor cells, and consistently manifest a trend toward neuronal rather than glial differentiation.

Multifocal glioblastoma with liver metastases in the absence of surgery. Case report

A patient with two intracerebral glioblastomas of differing histology with metastases to the liver in the absence of surgery is reported. The gliomatous nature of the lesions was confirmed by staining for glial fibrillary acidic protein. Histological and immunohistochemical evidence suggests that the metastases arose from the more poorly differentiated of the intracerebral tumors. One of the intracerebral tumors had enhanced expression of the ras p21 oncogene as compared to the other tumors and as compared to nonmalignant brain tissue from this patient.

Primary intracranial rhabdomyosarcoma: report of two cases

Primary intracranial rhabdomyosarcoma (RMS) is a rare tumor in infancy and childhood that is found in various locations in the central nervous system. The clinical course worsens rapidly, and the final outcome is poor, with a median survival time of 8-10 months. Invasion of the meninges, spontaneous intratumoral bleeding, spinal leptomeningeal CSF spreading of tumor cells, and early recurrence of the mass are the distinctive features of RMS. Diagnosis of RMS may be missed: immunohistochemical staining using specific markers (myoglobin, myosin, desmin, vimentin, enolase), along with ultrastructural studies, provide the basis for making the final diagnosis. Treatment of RMS includes surgical excision, craniospinal radiation therapy, and chemotherapy. We report two cases of primary RMS in the CNS located in the posterior fossa and frontotemporal area. Both children underwent total surgical removal of the mass. Early recurrence of the tumor mass was noticed in both patients 2 months after surgery. Both children died shortly thereafter.

Choroid plexus papillomas: an immunohistological study of 16 cases

Eleven benign and five malignant choroid plexus papillomas in children and adults were studied immunohistologically with a panel of antibodies against glial fibrillary acidic protein, S-100 protein, vimentin, desmin, epithelial membrane antigen and two different cytokeratins (LP34 and CAM 5.2). Glial fibrillary acidic protein was focally present in epithelial tumour cells, in cells within solid areas and in clusters of cells within the stroma. S-100 protein was diffusely present in tumour cells with focal accentuation. Vimentin was present in all cases, the epithelial tumour cells demonstrating strong and diffuse positivity with perinuclear accentuation; malignant tumours, however, showed stronger positivity than benign ones. Desmin was negative in all tumours. Epithelial membrane antigen and cytokeratin (LP34) were demonstrated in four of five malignant tumours but were absent in the benign ones; CAM 5.2 reacted with four of five malignant tumours and also reacted with eight of the 11 benign ones. The significance of these findings is discussed in respect of the ontogeny of these tumours.