[Investigation of a new highly porous hydroxyapatite matrix for obliterating open mastoid cavities - application in guinea pigs bulla]. / Untersuchung von hochporösem Knochenaufbaumaterial zur Mastoidhöhlenobliteration- Intrabulläre Applikation beim Meerschweinchen.

BACKGROUND: Many different techniques for obliterating open mastoid cavity have been described. The results after the application of alloplastic materials like Hydroxyapatite and Tricalciumphosphate were poor due to long-lasting resorption. Extrusion of those materials has been described. We investigated the applicability of a new high-porosity ceramic for obliterating large open mastoid cavities and tested it in an animal model (bulla of guinea pig). METHODS: A highly porous matrix (NanoBone) bone-inductor fabricated in a sol-gel-technique was administered unilaterally into the opened bullae of 30 guinea pigs. In each animal the opposite bulla was filled with Bio-Oss, a bone substitute consisting of a portion of mineral bovine bone. Histological evaluations were performed 1, 2, 3, 4, 5 and 12 weeks after the implantation. RESULTS: After the initial phase with an inflammatory reaction creating a loose granulation tissue, we observed the formation of trabeculare bone within the fourth week in both groups. From the fifth week on we found osteoclasts on the surface of NanoBone and Bio-Oss with consecutive degradation of both materials. CONCLUSION: In our animal model study we found beneficial properties of the used bone-inductors NanoBone and Bio-Oss for obliterating open mastoid cavities.

[Myxoma of the middle ear-a rare cause of facial palsy]. / Das Myxom des Mittelohrs als mögliche Ursache einer temporären Fazialisparese.

In case of the co-occurrence of facial palsy and inflammation-like symptoms of the same ear, the differential diagnosis is focused on viral (herpes zoster) or bacterial diseases. We report a patient for whom the surgical exploration of the middle ear revealed a benign tumor: a myxoma. These neoplasias are rare tumors in the head and neck region. The typical tumor site is the atrium of heart. In the ear, the tumor grows slowly and remains asymptomatic unless it irritates structures such as the facial nerve or the vestibular organ. Histologically, the tumor presents a "myxoid" matrix that is rich in acid mucopolysaccarides. The treatment of choice is complete surgical resection. Using the case presented, we discuss the causality between the tumor and the facial palsy, although during the operation the bony canal of the nerve was found to be intact. In any cases with clinically and radiologically unclear findings of the ear in connection with facial palsy, surgical exposure should be considered.

A radiation-induced gene signature distinguishes post-Chernobyl from sporadic papillary thyroid cancers.

We investigated selected gene targets to differentiate radiation-induced papillary thyroid cancers (PTCs) from other etiologies. Total RNA was isolated from 11 post-Chernobyl PTCs and 41 sporadic PTCs characterized by a more aggressive tumor type and lacking a radiation exposure history. RNA from 10 tumor samples from both groups was pooled and hybridized separately on a whole genome microarray for screening. Then 92 selected gene targets were examined quantitatively on each tumor sample using an RTQ-PCR-based low-density array (LDA). Screening for more than fivefold differences in gene expression between the groups by microarray detected 646 up-regulated and 677 down-regulated genes. Categorization of these genes revealed a significant (P < 0.0006) over-representation of the number of up-regulated genes coding for oxidoreductases, G-proteins and growth factors, while the number of genes coding for immunoglobulin appeared to be significantly down-regulated. With the LDA, seven genes (SFRP1, MMP1, ESM1, KRTAP2-1, COL13A1, BAALC and PAGE1) made a complete differentiation between the groups possible. Gene expression patterns known to be associated with a more aggressive tumor type in older patients appeared to be more pronounced in post-Chernobyl PTC, thus underlining the known aggressiveness of radiation-induced PTC. Seven genes were found that completely distinguished post-Chernobyl (PTC) from sporadic PTC.

Rb-loss is associated with high malignancy in chondrosarcoma.

Loss of function of the human retinoblastoma gene (Rb) is a frequent genetic abnormality in human malignancies and causes a disturbance in the cell cycle and loss of normal proliferation and differentiation. We studied the loss of heterozygosity (LOH) of the Rb gene in 31 formalin-fixed, paraffin-embedded cartilaginous tumors using polymerase chain reaction. The tumors were subdivided into 8 cases of dedifferentiated (DD) chondrosarcoma, 17 cases of conventional chondrosarcoma (nine grade 1, seven grade 2 and one grade 3), 4 enchondromas and 2 chondroblastomas. Both components of DD chondrosarcoma, the low-grade and anaplastic components, were separated by a microdissection approach. The genetic data were correlated with the expression of the Rb protein examined by Rb immunohistochemistry. We found Rb-LOH in one grade 3 chondrosarcoma, and in the anaplastic component in 7 of 8 cases of DD chondrosarcoma (89% of all high-grade chondrosarcomas). All tumors with Rb-LOH were immunohistochemically Rb-negative. The only case of DD chondrosarcoma negative for Rb-LOH in both components of the tumor also showed weak expression of the Rb protein in the anaplastic component. All benign cartilaginous tumors, low-grade chondrosarcomas and low-grade tumor components of DD chondrosarcomas were negative regarding Rb-LOH but positive in Rb immunohistostaining. We concluded that Rb-LOH predominantly occurs in high-grade chondrosarcomas. However, it is not a marker for identifying low-grade tumors with a tendency towards progression or local recurrence.

A case of Brooke-Spiegler syndrome with a novel mutation in the CYLD gene in a patient with aggressive non-Hodgkin's lymphoma.

PURPOSE: Brooke-Spiegler syndrome (BSS, familial cylindromatosis) is a rare hereditary disease characterized by multiple tumors of the skin appendages predominantly located in the head and neck region, such as cylindromas, trichoepitheliomas, or spiradenomas. It is caused by an autosomal dominant mutation in the CYLD gene, mapped on chromosome 16q12-13. Association with secondary malignant neoplasms has been reported. Until now 51 different mutations in 73 families have been reported; 41 % of them constitute frameshift mutations, resulting in an interruption of the expression of the gene product CYLD. CYLD is a deubiquitinating enzyme and plays an important role in (NF)-κB pathway signaling, a central pathway for apoptosis regulation. Mutation-induced loss of function leads to constitutive activation of NF-κB. METHODS: Here, we report the case of a 48-year-old female patient diagnosed with an abdominal aggressive non-Hodgkin's lymphoma. The patient presented with multiple cylindromas of the capillitium. The patient's mother also has a mild form of late-onset cylindromas. Due to the typical clinical features indicating BSS, genotyping from peripheral blood was performed. A c.2465insAACA mutation in exon 17 of the CYLD gene, leading to a frameshift, was detected in the patient and in the patient's mother. RESULTS/CONCLUSIONS: This is the first description of this hereditary mutation in exon 17 of the CYLD gene. There have been several reports on patients with CYLD mutations and different types of malignancies. However, a coincidence with aggressive non-Hodgkin's lymphoma has not been reported yet.

Spatial and temporal disease progression of adult-onset subacute sclerosing panencephalitis.

An adult-onset case of subacute sclerosing panencephalitis with occipitofrontal spread of the infection documented clinically and by MRI is reported. Autopsy revealed numerous intranuclear viral inclusions and widespread demyelination in both frontal lobes. In the occipital lobes where the disease started 5 years previously, inclusions were rare, but degenerative tissue changes were prominent. This case underlines the importance of measles virus migration for the progression of this fatal disorder.

GRO-alpha in normal and pathological thyroid tissues and its regulation in thyroid-derived cells.

Thyroid glands affected by Graves' disease (GD) show striking leukocytic infiltration, mainly by T-cells. The mechanisms by which the various leukocytes are maintained in the thyroid are unknown. Growth-regulated oncogene-alpha (GRO-alpha) in interaction with its receptor CXCR2 is a chemoattractant for both T-cells and neutrophils and may be one of the chemokines involved in the cell maintenance. GRO-alpha and CD18 mRNA as a marker of leukocytic infiltration were quantified in thyroid tissue using competitive RT-PCR. We found very high GRO-alpha mRNA levels in all thyroid tissues. In GD patients (n=16), the GRO-alpha mRNA did not correlate with the CD18 mRNA level or thyroid peroxidase and TSH-receptor antibodies in patients' sera. In thyroid autonomy (n=10), the GRO-alpha mRNA levels were significantly lower in autonomous single adenomas compared with the corresponding normal tissue. In order to define the cellular source of GRO-alpha mRNA and protein, we examined various thyroid-derived cells. Thyrocytes, thyroid-derived leukocytes and fibroblasts showed basal GRO-alpha mRNA and protein expression, which was remarkably upregulated by different stimuli in vitro. The expression of GRO-alpha by thyroid carcinoma cell lines confirms that thyrocytes may actually produce GRO-alpha. As shown by flow cytometry and immunohistology, CD68+ monocytes/macrophages are the only cell population strongly expressing CXCR2 in the thyroid.

Distinction between lipoma and liposarcoma by MDM2 alterations: a case report of simultaneously occurring tumors and review of the literature.

We investigated a lipoma and a well-differentiated/dedifferentiated liposarcoma (WD/DDL), occurring simultaneously in one patient for the possible role of p53 and mdm2 in the molecular oncogenesis of liposarcoma and tumor progression. The hypothesis tested was if there is a continuum in the development from lipoma to liposarcoma. Lipoma was characterized by a lack of p53 mutation, p53 LOH and p53 protein expression, as well as by mdm2 amplification and mdm2 protein expression. p53 mutation and p53 LOH were found neither in the well-differentiated nor in the dedifferentiated parts of the liposarcoma. In contrast, mdm2 amplification and an increase in mdm2 protein expression were found to be associated with malignancy and dedifferentiation, whereas p53 protein expression was only slightly increased. These findings indicate that mdm2 constitutes one of the most common targets for molecular aberration in WD/DDL. We suggest that mdm2 is a marker distinguishing between ordinary lipoma and well-differentiated liposarcoma, and that the genesis of these tumors is different.

Genetic and epigenetic alterations in tumor progression in a dedifferentiated chondrosarcoma.

In this case of a dedifferentiated chondrosarcoma, we searched for genetic or epigenetic alterations in both components of the tumor, the low grade chondroblastic component, and the high grade osteosacomatouscomponent. To date, only little is known about aberrant patterns of DNA methylation in chondrosarcomas. Microdissection was used as a valuable method for clearly separating the tissues. We examined CpG island methylation of 8 tumor suppressor genes and candidate tumor suppressor genes, which are involved in different pathways: cell cycle (p21WAF1, p16INK4, p14ARF), apoptosis (DAPK, FHIT), DNA repair (hMLH1), and cell adherence (E-Cadherin). We found p16INK4 and E-cadherin promotor methylation in the low grade chondroid compartment of the dedifferentiated chondrosarcoma. P16INK4, FHIT, and E-cadherin were methylated in the highly malignant osteosarcomatous compartment of the tumor. Earlier investigations of this chondrosarcoma showed p53 mutation and p53-LOH in the anaplastic component. As shown in this case, it was accompanied by Rb-LOH. Early methylation of p16IK4 and E-cadherin in the chondroid compartment could point to the monoclonal origin of demonstrated dedifferentiated chondrosarcoma. Further alterations, as shown in p53, Rb and FHIT, are responsible for the "switch" to a high grade anaplastic sarcoma.

Different mRNA expression profile during tumor progression in a well-differentiated liposarcoma--A microdissection approach.

Like malignant fibrous histiocytoma (MFH), dedifferentiated liposarcoma represents a distinct subtype of liposarcoma and is characterized by an abrupt transition from well-differentiated liposarcoma (WDL) to highgrade dedifferentiated liposarcoma (DDL) . In addition, specific cytogenetic aberrations support the close biological relationship between WDL and DDL. Recent observations indicated the significance of cell cycle aberrations in tumor progression from the low-malignant, well differentiated to its dedifferentiated form, the prognosis of which is poor. Thus, alterations of mdm2 and p53 genes belong to the most frequently reported alterations in these two subtypes of liposarcoma. In previous investigations, we reported that loss of heterozygosity at the Rb gene locus, telomerase activity, hTERT, and c-Myc expression were associated with tumor progression in liposarcomas. In this study, we report on a case of a WD/DDL, in which both tumor components were separated using laser microdissection (P.A.L.M.) for the investigation of hTERT mRNA expression on a LightCycler. Macroscopically selected and histologically proven cryosections of low malignant and highly malignant tumor areas were cytogenetically investigated to confirm the diagnosis and to find additional chromosomal alterations with tumor progression.

[Juvenile laryngeal papillomatosis--immunisation with the polyvalent vaccine gardasil]. / Juvenile Larynxpapillomatose--Impfung mit dem polyvalenten Spaltimpfstoff Gardasil.

Juvenile laryngeal papillomatosis is a rare condition caused by human papilloma virus (HPV). In cases with rapid recurrences permanent impairments of voice and breathing are almost inevitable due to the frequent need of debulking surgeries. Efforts to lower the recurrence rate comprise the adjuvant use of interferon alpha, local cidofovir, photodynamic therapy or mumps vaccination. In the present case we tried to positively influence the aggressive course of disease in a two year old boy by immunisation with the quadrivalent HPV vaccine Gardasil(R). Chromogenic in-situ hybridisation analysis and polymerase chain reaction (PCR) of lesion tissue showed simultaneous infection with the HPV-Types 6 and 11. After the third immunisation the disease became stable. No further surgery was necessary for the last ten months. The risk profile of this adjuvant treatment is low. We think it worth to initiate a multicentre trial to prove a benefit of this treatment even if no complete virus elimination can be achieved.

Close localization of DAP-kinase positive tumour-associated macrophages and apoptotic colorectal cancer cells.

The death-associated protein kinase (DAP-kinase) is a cytoskeleton-associated protein crucially involved in the induction of early apoptotic pathways. Aberrant hypermethylation of the DAP-kinase promoter plays a major role in tumorigenesis. We aimed to investigate the inactivation of DAP-kinase and its association with apoptotic cell death in 94 colorectal carcinomas. DAP-kinase promoter hypermethylation and mRNA expression were investigated using methylation-specific PCR and real-time RT-PCR, respectively. The expression of DAP-kinase, Fas, and Fas-ligand (FasL) proteins was studied by immunohistochemistry and immunofluorescence. Apoptosis of tumour cells was investigated using the TUNEL assay. DAP-kinase was expressed in tumour cells and tumour-invading macrophages and was closely associated with high numbers of apoptotic tumour cells. DAP-kinase expression co-localized with FasL overexpression in tumour-associated macrophages, and aberrant promoter hypermethylation was verified in more than 50% of carcinomas. There was a tendency for proximal tumours to show DAP-kinase promoter methylation more frequently (p = 0.07). Promoter methylation resulted in a decrease or loss of DAP-kinase protein expression in tumour cells and tumour-associated macrophages. Simultaneously, a decreased apoptotic count and loss of Fas/FasL expression was observed in tumour cells. Our study is the first to demonstrate DAP-kinase expression in invading tumour-associated macrophages in colorectal cancer. The presence of similar expression levels of DAP-kinase in tumour cells and associated macrophages, and their dependence on the promoter methylation status of the tumour cells, suggests cross talk between these cell types during apoptotic cell death.

[Telomerase and new aspects for tumor biology]. / Telomerase und neue Aspekte in der Tumorbiologie.

The field of tumor genetics is characterized by a whole string of unsolved questions that affect both the basics of tumorigenesis and the possibilities of using molecular markers at the clinical level. Telomerase, an enzyme that has the capability of unlimitedly maintaining the division of immortal cells, can nowadays be demonstrated with the use of up-to-date molecular biological methods. In vitro experiments have now succeeded in changing normal cells into tumor cells via transfection with telomerase. The regulatory mechanisms and interactions of telomerase are presently the subject of intensive research. Telomerase activity plays a crucial role even in present day diagnostic procedures and the estimation of prognosis for certain tumor types. In comparison with normal tissues, increased telomerase activity in tumor tissues implies therapeutical possibilities with the use of telomerase inhibitors.

PTEN is not altered in sporadic vestibular schwannomas.

AIMS: To investigate the role of the tumour suppressor gene PTEN in the tumorigenesis and growth of sporadic vestibular schwannomas, and to characterize the cellular distribution of the PTEN protein in relation to the MIB-1 proliferation index in these tumour. METHODS AND RESULTS: Immunoexpression of the PTEN protein was observed within the neoplastic Schwann cells in 21 out of 30 sporadic schwannomas examined (70%). PTEN expression was consistently stronger in Antoni A areas than in Antoni B areas. High levels of PTEN immmunoexpression in schwannomas were associated with an increased MIB-1 labelling index. Occasionally, vascular endothelial cells also showed PTEN immunoreaction. By polymerase chain reaction-single strand conformation polymorphism screening, no mutations were found in the complete protein coding region of the PTEN gene. CONCLUSIONS: The PTEN tumour suppressor gene is expressed in the majority of sporadic schwannomas. The maintained expression of the PTEN protein, together with the lack of detectable mutations in this gene, suggests that the function of the PTEN tumour suppressor gene is not altered in sporadic vestibular schwannomas.

Prophylaxis of peritoneal carcinomatosis in experimental investigations.

BACKGROUND AND AIMS: We compared the effectiveness and side effects of various cytostatic agents for use in perioperative intraperitoneal irrigation to prevent peritoneal carcinomatosis. METHODS: The adenocarcinoma cell line CC-531 was implanted during laparotomy at the mesenterial trunk of anesthetized male WAG rats. Direct perioperative intraperitoneal chemotherapy was performed after 5 min with either 5-fluorouracil, cisplatin, or mitomycin; controls received only tumor cells. The animals were inspected daily over 30 days for side effects. They were then killed, and the greater omentum and mesentery were resected, the tumor mass was examined for the presence of peritoneal carcinomatosis, and tumor nodules in the greater omentum and mesentery were counted. RESULTS: All the animals in the control group developed histologically confirmed peritoneal carcinomatosis. Animals receiving cisplatin or mitomycin by direct intraperitoneal perioperative chemotherapy showed no macroscopic or histological evidence of tumor growth. Two animals in the fluorouracil group had macroscopically and histologically manifest tumor growth; another animal showed only histological evidence of malignancy. Substantial side effects were noted in the cisplatin group, with all animals experiencing bleeding in the peritoneum and toxic necrotic reactions of the colon; two animals died of these side effects. CONCLUSION: Direct intraperitoneal chemotherapy with cisplatin or mitomycin prevents peritoneal carcinomatosis in experimental investigations.

[Role of the class II tumor suppressor gene maspin in thyroid carcinogenesis]. / Die rolle des Klasse II Tumorsuppressorgens Maspin in der thyreoidalen Karzinogenese.

The presented study was aimed to investigate new mechanisms of carcinogenesis in thyroids at the molecular level and to find potential protein markers involved in the initiation of the different histological subtypes of thyroid carcinoma. For this, we performed differential proteome analysis on primary cultured thyrocytes and transformed thyrocytes derived from 238Pu alpha-particle irradiation using two-dimensional electrophoresis (2-DE) and peptide mass fingerprinting (PMF) with matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF MS). Proteome analysis identified a strong upregulation of maspin, a serine protease inhibitor and class II tumor suppressor, in irradiated thyrocytes. To clarify the role of maspin in thyroid carcinogenesis, we searched for mRNA/protein expression in 30 normal (tumor-free) thyroid tissues, 35 follicular adenomas, 68 papillary carcinomas, 38 follicular carcinomas, 25 poorly differentiated carcinomas, and 34 undifferentiated carcinomas and compared the results with maspin promoter methylation status, p53 expression, clinicopathological data and prognosis. Maspin expression was detectable in 48 of 68 papillary carcinomas exclusively. There was a low methylation rate of 28% in papillary carcinomas in contrast to the other tissues (89-100%). p53 was positive in 2% of maspin positive cases, and in 80% of maspin negative cases. After 110 month follow-up 83% of the maspin positive patients had recurrence-free disease, whereas only 40% of the maspine negative patients were recurrence-free. Our data suggest: (1) maspin expression is a special feature of papillary thyroid carcinomas, (2) promotor methylation-caused maspin repression plays a major role in gene balance and in the process of tumor determination, (3) maspin protein possibly functions as a clinically relevant inhibitor of tumor progression, (4) our data delivers the hints for a p53-depentent regulatory pathway of the maspin protein in human cancer.

Prevention and treatment of peritoneal carcinomatosis in experimental investigations with CPT-11 and oxaliplatin.

Following surgical resection of colorectal carcinoma, local recurrence in the tumor bed or in the mesentery remains a frequently encountered problem. Currently there are no recognized standard therapy protocols for the prevention of local recurrence or the treatment of peritoneal carcinomatosis. The aim of our trial was to investigate whether CPT-11 and oxaliplatin could decrease i.p. tumor growth in a basic experimental animal model. Experiments were performed on three groups of animals plus controls. In the first group, the cytostatic agents were applied directly following tumor cell implantation into the peritoneal cavity. In the second group, early postoperative i.p. chemotherapy (days 5, 10 and 15 following surgery) was administered. In the third group, late i.p. chemotherapy (days 15, 20 and 25 after tumor cell transfer) was administered with the intention of reducing a manifest peritoneal carcinomatosis. The trial also set out to describe any side effects observed following i.p. administration. The results indicated that CPT-11 and oxaliplatin were highly effective in reducing i.p. tumor spread after direct i.p intraoperative application. Intraperitoneal administration of CPT-11 or oxaliplatin also decreased i.p. tumor growth after early i.p. chemotherapy. CPT-11 was a little more effective with lower side effects. However, it was clear that it was not possible to treat a manifest peritoneal carcinomatosis in this way.

[Biallelic inactivation of the p16-Gen in a metachronous triple carcinoma in the oropharyngeal region]. / Biallelische Inaktivierung des p16-Gens bei metachronem Dreifachkarzinom im oropharyngealen Bereich.

AIMS: Recent studies have shown that most Dutch families with atypical multiple-mole melanoma (FAMMM) have a 19-bp deletion (p16-Leiden) in exon 2 of the p16 gene. Apart from reports on metachronous pancreatic tumors, other cancer types have never been described in such families. Due to heterozygous p16-Leiden constitution, our proband with multiple head and neck carcinomas was a suitable model for studying the type of p16 inactivation according to the Knudson-two-hit model. METHODS: p16 mutations in exons 1 and 2 were determined using PCR-SSCP-Sequencing analysis. p16 methylation was assessed by methylation-specific PCR. RESULTS: All three metachronous (larynx, pharynx, oral cavity) tumors had a methylated p16 promotor. The p16 protein loss detected by immunohistochemistry clearly confirmed a complete loss of p16 tumor suppressor function. Thus, all three tumors exhibited biallelic inactivation of p16, caused by aberrant methylation of the p16 promotor. CONCLUSIONS: This is the first report on p16-Leiden mutation in head and neck cancer. We provide evidence that the somatic methylation of p16 promotor is associated with the germline transmission of p16-Leiden mutation. This is an example for the rare event of in which aberrant methylation acting as the 'second hit' in a familial cancer syndrome. Our results show that this epigenetic event is equivalent to genetic alterations (mutation/LOH) confirming the Knudson's hypothesis for tumor suppressor gene inactivation.

Pineal epidermoid coinciding with pineocytoma.

Tumours of the pineal region are uncommon. We report on a 62-year-old male presenting with Parinaud's syndrome and aqueduct stenosis caused by a cystic tumour in the pineal region. During surgery, adjacent to the cystic tumour, a second smaller tumour was identified, which was clearly separate from the first tumour and from the pineal gland. Histological examination disclosed the cystic tumour as an epidermoid cyst, whereas the second tumour demonstrated histological and immunohistochemical features of a pineocytoma. The unique finding of two different types of tumours in the pineal region is evaluated with regard to the histogenesis of epidermoid cysts and pineocytomas.

Molecular targets for tumour progression in gastrointestinal stromal tumours.

BACKGROUND AND AIMS: The distinction between benign and malignant gastrointestinal stromal tumours (GISTs) is often unclear at the clinical and histopathology levels. GISTs are believed to arise from the stem cells of Cajal. In order to define genetic biomarkers and identify target genes related to GIST progression, we analysed and compared benign and malignant GISTs with verified follow up data using cDNA expression arrays. METHODS: Eight genes were frequently overexpressed in malignant GISTs and their overexpression was confirmed using quantitative real time reverse transcription-polymerase chain reaction. These genes included ezrin (villin 2 (VIL2)), collagen 8 alpha 1 subunit (COL8A1), G2/mitotic specific cyclin B1 (CCNB1), high mobility group protein (HMG2), TSG101 tumour susceptibility protein, CENP-F kinetochore protein, protein tyrosine kinase 2 (FAK), and protein kinase DYRK2. To test these genes in a clinical setting, we obtained diagnostic samples of 16 additional GISTs that were classified at diagnosis as benign, malignant, and uncertain malignant potential (UMP). RESULTS: There was remarkable gene overexpression in all malignant GISTs. Statistical analyses revealed significant correlations between overexpression of several gene pairs in malignant GISTs. We found the strongest correlations (rho>0.70) among the significant correlations (p<0.01) between CCNB1-CENP-F (rho = 0.87) and CCNB1-FAK (rho = 0.73). Gene expression of the UMP GISTs suggested two different groups. Three UMP GISTs had gene expression consistent with malignant tumours and their follow up data revealed that indeed these patients had recurrences later on. On the other hand, UMP GISTs that had low gene expression levels continued free of disease for several years. CONCLUSIONS: These results provide insight into the oncogenesis of GISTs and suggest that testing the expression profile of a number of genes may segregate GISTs into groups of different tumour behaviour.