Distantly Metastatic Retinoblastoma to Soft Tissue and Bone: A Challenging Diagnosis Highlighting the Utility of CRX.

Distant metastasis of retinoblastoma to sites outside the central nervous system is rare; such cases may present years following primary treatment. Diagnosis may be difficult given the rarity of such events and considerable histologic mimics. We describe the clinicopathologic features of 6 cases of metastatic retinoblastoma to distant bone and soft tissue sites from 2 large academic centers. Patients were 3 female and 3 male children; median age was 9.5 years (range: 5 to 15 y) with a mean interval from primary disease diagnosis of 8.0 years (range: 0.75 to 14 y). Metastasis to bones of the lower extremities was most common, occurring in 4 of 6 cases. Tumors showed typical histologic features of retinoblastoma, with sheets of primitive round cells with minimal cytoplasm and indistinct nucleoli; however, characteristic Flexner-Wintersteiner rosettes were absent. A subset of cases demonstrated an alveolar growth pattern, and 2 cases showed higher grade cytology with nuclear anaplasia and prominent nucleoli. Immunohistochemistry for CRX and RB1 showed uniform positivity and loss of expression, respectively. Metastatic retinoblastoma outside the central nervous system may present following long disease-free intervals. Immunohistochemistry for CRX is helpful to confirm this challenging diagnosis.

Diagnostic efficacy of cell block method for vitreoretinal lymphoma.

BACKGROUND: Vitreoretinal lymphoma (VRL) is a life- and sight-threatening disorder. The aim of this study was to analyze the usefulness of the cell block method for diagnosis of VRL. METHODS: Sixteen eyes in 12 patients with VRL, and 4 eyes in 4 patients with idiopathic uveitis presenting with vitreous opacity were enrolled in this study. Both undiluted vitreous and diluted fluids were isolated during micro-incision vitrectomy. Cell block specimens were prepared in 19 eyes from diluted fluid containing shredding vitreous. These specimens were then submitted for HE staining as well as immunocytological analyses with antibodies against the B-cell marker CD20, the T-cell marker CD3, and cell proliferation marker Ki67. Conventional smear cytology was applied in 14 eyes with VRL using undiluted vitreous samples. The diagnosis of VRL was made based on the results of cytology, concentrations of interleukin (IL)-10 and IL-6 in undiluted vitreous, and immunoglobulin heavy chain gene rearrangement analysis. RESULTS: Atypical lymphoid cells were identified in 14 out of 15 cell block specimens of VRL (positive rate: 93.3 %), but in 5 out of 14 eyes in conventional smear cytology (positive rate: 35.7 %). Atypical lymphoid cells showed immunoreactivity for CD20 and Ki67. Seven cell block specimens were smear cytology-negative and cell block-positive. The cell block method showed no atypical lymphoid cells in any patient with idiopathic uveitis. CONCLUSIONS: Cell block specimens using diluted vitreous fluid demonstrated a high diagnostic sensitivity and a low pseudo-positive rate for the cytological diagnosis of VRL. The cell block method contributed to clear differentiation between VRL and idiopathic uveitis with vitreous opacity.

Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy: An analytical technique to understand therapeutic responses at the molecular level.

Rapid monitoring of the response to treatment in cancer patients is essential to predict the outcome of the therapeutic regimen early in the course of the treatment. The conventional methods are laborious, time-consuming, subjective and lack the ability to study different biomolecules and their interactions, simultaneously. Since; mechanisms of cancer and its response to therapy is dependent on molecular interactions and not on single biomolecules, an assay capable of studying molecular interactions as a whole, is preferred. Fourier Transform Infrared (FTIR) spectroscopy has become a popular technique in the field of cancer therapy with an ability to elucidate molecular interactions. The aim of this study, was to explore the utility of the FTIR technique along with multivariate analysis to understand whether the method has the resolution to identify the differences in the mechanism of therapeutic response. Towards achieving the aim, we utilized the mouse xenograft model of retinoblastoma and nanoparticle mediated targeted therapy. The results indicate that the mechanism underlying the response differed between the treated and untreated group which can be elucidated by unique spectral signatures generated by each group. The study establishes the efficiency of non-invasive, label-free and rapid FTIR method in assessing the interactions of nanoparticles with cellular macromolecules towards monitoring the response to cancer therapeutics.

Subretinal heterotopic respiratory epithelium: a case report and literature review.

A 51-year-old female underwent vitrectomy surgery to remove a group of spherical subretinal tumors beneath the detached retina. Hematoxylin and eosin staining and immunohistochemical findings showed that the characteristics of the tumor were consistent with a subretinal heterotopic respiratory epithelium. This is the first report of a respiratory epithelial heterotopia located in the subretinal space.

[Efficacy of intravitreal carboplatin plus bevacizumab in refractory retinoblastoma].

OBJECTIVES: To evaluate the efficacy of intravitreal carboplatin plus bevacizumab in refractory retinoblastoma. METHODS: Perspective study.Eleven patients (11 eyes) with the diagnosis of refractory retinoblastoma were enrolled in Department of Ophthalmology of Peking University People's Hospital from June 2013 to March 2014. They underwent intravitreal carboplatin plus bevacizumab every 4 weeks, an average of 4.5 times of treatment.Observe for 3 months after the last treatment. Aqueous humor was taken for cytological and VEGF detection and retinal funds were taken photos for observation.Statistical analyses between experimental group and control group and before and after intravitreal injection within experimental group were performed with independent samples t test. RESULTS: Tumor in vitreous cavity reduced significantly in seven patients, however, poor control in four cases, and three of them were recurrent after first-line treatment. Cytology detection for aqueous humor showed no tumor cells in all of them. Aqueous VEGF of patients with retinoblastoma (60.65 ± 6.20) was significantly higher than the control group (21.98 ± 6.91). The difference was statistically significant (t = 13.80, P < 0.01). And the aqueous VEGF content decreased significantly after treatment (t = 2.12, P < 0.05). CONCLUSION: Intravitreal carboplatin plus bevacizumab, is a relatively safe, effective treatment for refractory retinoblastoma, however, ineffective for recurrent tumor.

Immunoreactivity of the 14F7 Mab raised against N-Glycolyl GM3 Ganglioside in retinoblastoma tumours.

INTRODUCTION: The identification of molecules expressed selectively on the surface of retinoblastoma cells would allow applying targeted therapies. The Ganglioside, N-Glycolyl-GM3 (NeuGc-GM3), is an attractive candidate, as it has been detected in other paediatric neuroectodermic tumours, and it is not expressed in human normal tissues. The 14F7 antibody recognizes specifically the ganglioside NeuGc-GM3. PURPOSE: To characterize the expression of NeuGc-GM3 in retinoblastoma cell lines and in retinoblastoma tumours using the 14F7 monoclonal antibody. METHODS: We studied WERI-Rb1 and Y79 cell lines, 24 retinoblastoma primary tumours from unilateral and bilateral cases and two bone marrow biopsies from metastatic retinoblastoma. Tumours were classified into three groups: non-invasive (n = 13), invasive (n = 9) and metastatic (n = 2). Three eyes enucleated because of non-tumoural conditions were used as controls. Cell lines and tumour sections were studied by immunohistochemistry using the 14F7 antibody. NeuGc-GM3 expression was evaluated by analysing the percentage of positive tumoural cells and the staining intensity. These parameters were analysed comparatively among the three groups. RESULTS: Both retinoblastoma cell lines showed immunoreactivity to NeuGc-GM3 but WERI-Rb1 presented higher intensity than Y79. All the tumours studied showed strong immunoreactivity to NeuGc-GM3 with no significant differences among groups. In both bone marrow specimens, NeuGc-GM3 immunoreactivity was observed in retinoblastoma cells. In bilaterally enucleated cases, NeuGc-GM3 immunoreactivity was not altered before and after chemotherapy. Non-tumoural retinas were negative. CONCLUSIONS: NeuGc-GM3 is highly expressed in retinoblastoma cell lines, tumours and metastatic cells to the bone marrow, and it is not detectable in control eyes. There were no significant differences in the immunoreactivity to 14F7 among tumours from different disease stages. Its immunoreactivity did not change after chemotherapy.

p16(INK4a) expression in retinoblastoma: a marker of differentiation grade.

BACKGROUND: The tumor suppressor protein p16(INK4a) has been extensively studied in many tumors with very different results, ranging from its loss to its clear overexpression, which may be associated with degree of tumor differentiation and prognosis. However, its expression remains unclear in human retinoblastoma (RB), a common malignant tumor of retina in childhood. The aim of this study was to explore the expression pattern of p16(INK4a) in RB, and the correlation between p16(INK4a) expression and histopathological features of RB. METHODS: Sixty-five cases of RB were retrospectively analyzed. Paraffin-embedded blocks were retrieved from the archives of ocular pathology department at Zhongshan Ophthalmic Center of Sun Yat-sen University, China. Serial sections were cut and subjected to hematoxylin and eosin staining. Immunohistochemical staining was further done with antibodies p16(INK4a), CRX and Ki67. The correlation of p16 (INK4a) expression with CRX and Ki67 and clinicopathological features of RB were analyzed. RESULTS: RB tumor histologically consists of various differentiation components including undifferentiated (UD) cells, Homer-Wright rosettes (HWR) or Flexner-Winterstein rosettes (FWR) and fleurettes characteristic of photoreceptor differentiation or Retinocytoma (RC). p16(INK4a) expression was negative in both fleurette region and the residual retinal tissue adjacent to the tumor, weakly to moderately positive in FWR, strongly positive in both HWR and UD region. However, CRX had the reverse expression patterns in comparison with p16(INK4a). It was strongly positive in photoreceptor cells within the residual retina and fleurettes, but weakly to moderately positive in UD area. Together with Ki67 staining, high p16(INK4a) expression was associated with poor histological differentiation of RB tumors, which had higher risk features with the optic nerve invasion and uveal invasion. CONCLUSIONS: p16(INK4a) expression increased with the decreasing level of cell differentiation of RBs. RB tumors extensively expressing p16(INK4a) tended to have higher risk features with poor prognosis. This study suggested that p16(INK4a) would be a valuable molecular marker of RB to distinguish its histological phenotypes and to serve as a predictor of its prognosis. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_180.

Immunohistochemical expression of CD117 and vascular endothelial growth factor in retinoblastoma: possible targets of new therapies.

CD117 (C-kit) is thought to play an important role in tumourigenesis. There are limited data in the literature concerning C-kit expression in retinoblastoma. To date, no immunohistochemical studies have been performed to assess the possible association of C-kit with vascular endothelial growth factor (VEGF) in retinoblastoma. This study was designed to investigate C-kit and VEGF immunoexpression in retinoblastoma, their relationship with prognostic parameters as well as the correlation between them. A prospective immunohistochemical study was conducted on 56 retinoblastoma cases. Patients who had received preoperative chemotherapy were excluded. Positive C-kit and VEGF immunoreactivity was observed in 48.2% and 76.8% of retinoblastoma cases respectively. No C-kit immunostaining was seen in the adjacent uninvolved retina. However, VEGF expression was detected within its vasculature. Retinoblastomas with combined pattern of tumour growth revealed a highly significant positive C-kit expression (P = 0.002) compared to cases with endophytic or exophytic growths. Also, positive C-kit expression was statistically higher in cases with optic nerve invasion (P = 0.001) and choroidal invasion (P ≤ 0.01) compared to negative cases. A highly significant positive VEGF expression was detected in cases with optic nerve invasion (P = 0.013) compared to negative cases. Moreover, a highly significant positive correlation was detected between C-kit and VEGF expression (P = 0.006). C-kit is a feature of more aggressive retinoblastomas, with increased expression in tumours spreading beyond the retina. Moreover, VEGF is vastly expressed in retinoblastoma and is associated with optic nerve invasion. Both C-kit and VEGF may represent potential therapeutic targets for retinoblastomas.

Malignant teratoid medulloepithelioma with retinoblastic and rhabdomyoblastic differentiation.

We describe an unusual case of malignant teratoid medulloepithelioma in which distinct populations of tumor cells with different immunohistochemical staining patterns existed within the same eye. A neuroblastic population exhibited atypical features of retinoblastoma, including organization into pseudo-Flexner-Wintersteiner and Homer-Wright rosettes. Other populations evolved in strikingly different patterns, with large fields of cells resembling astrocytes and intervening streams of spindle cells that suggested smooth muscle. The spindle cell population was negative for smooth muscle antigen but stained positively for desmin, myoglobin, and myogenin. Under high magnification, the desmin, myoglobin, and myogenin-staining cells exhibited striations consistent with skeletal muscle differentiation.

Vitreoretinal presentation of secondary large B-cell lymphoma in patients with systemic lymphoma.

IMPORTANCE: Intraocular lymphomas represent a diverse group of hematologic malignant neoplasms involving different tissues within the eye. Predominant involvement of the retina and vitreous without uveal infiltration in systemic lymphoma, mimicking a primary vitreoretinal lymphoma, is extremely rare. Our study emphasizes the importance of systemic evaluation in addition to central nervous system evaluation in all patients with newly diagnosed vitreoretinal lymphoma. OBJECTIVE: To determine the incidence of secondary intraocular lymphoma presenting as vitreoretinal infiltrates without central nervous system involvement, mimicking primary vitreoretinal lymphoma in patients with systemic lymphoma. DESIGN Retrospective review of all vitreous aspiration biopsy samples acquired because malignant neoplasm was suspected clinically that were obtained at our institution from January 1, 2000, through December 31, 2010. Review included patient clinical history, radiographic study findings, cytologic and/or histologic preparations, immunophenotypic study findings, treatment, and outcomes. SETTING Mayo Clinic pathology database. PARTICIPANTS: Fifty-five patients with vitreous specimens available for review. EXPOSURES: Vitreous aspiration biopsy. MAIN OUTCOME AND MEASURE: Confirmation of the diagnosis of diffuse large B-cell lymphoma (DLBCL). RESULTS: Of the 55 patients with vitreous specimens available for review, 3 (5%) had a DLBCL infiltration in the vitreous without any central nervous system involvement as a manifestation of systemic lymphoma. All 3 patients were men, aged 54, 66, and 73 years, and had blurred vision and floaters for several weeks before undergoing diagnostic vitrectomy. Ophthalmic examinations revealed clumps of vitreous cells but no choroidal involvement. One patient had no history of lymphoma; the diagnosis of vitreoretinal lymphoma was followed by DLBCL after a lymph node biopsy. The other 2 patients had low-grade B-cell lymphoma and chronic lymphocytic leukemia for 29 and 7 months before large-cell transformation in the eye. Patients were treated with systemic chemotherapy plus intraocular injections of rituximab or methotrexate sodium. CONCLUSIONS AND RELEVANCE: Vitreoretinal symptoms of DLBCL in patients with systemic lymphoma may be more frequent than previously thought (5% in our study). Not all lymphomas with vitreoretinal involvement represent primary intraocular lymphomas; thorough ophthalmologic evaluation in patients with visual symptoms and complete staging in patients with documented ocular lymphoma are of utmost importance.

Adenoma of the retinal pigment epithelium: a report of 3 cases.

OBJECTIVE: To report the clinical manifestations and pathologic features of adenoma of the retinal pigment epithelium (RPE). DESIGN: Retrospective study. PARTICIPANTS: Three patients with an initial clinical diagnosis of choroidal melanoma. METHODS: Routine eye examinations, including visual acuity, intraocular pressure, slit-lamp examination, and ophthalmoscopy, were performed. Auxiliary examinations included fluorescein fundus angiography (FFA), indocyanine green angiography (ICGA), B-scan ultrasonography, colour Doppler imaging (CDI), and MRI. Endoresection of the tumours was performed, and the specimens underwent pathological examination. RESULTS: The tumours were of yellow-pink or brown colour and all located in the right eye. On FFA and ICGA, the tumours demonstrated hypofluorescence in the early phase and hyperfluorescence with prominent leakage in the late phase. CDI showed arterial blood signals in the tumour, and MRI showed hyperintensity in the T1-weighted image and hypointensity in the T2-weighted image. On pathological examination all the tumours were positive with periodic acid-Schiff, S-100, neurone-specific enolase, synaptophysin, epithelial membrane antigen, and vimentin staining but negative with melanoma-specific antigen HMB45, and cytokeratin. After 3 years of follow-up, there was no tumour recurrence and the retinas remained attached. CONCLUSIONS: RPE-derived adenoma is difficult to diagnose clinically. In most cases, pathological confirmation is needed. Local resection is a favorable alternative treatment for some patients.

Downregulation and aberrant promoter methylation of p16INK4A: a possible novel heritable susceptibility marker to retinoblastoma.

RB loss has long been recognized as the causative genetic alteration underlying retinoblastoma but it is increasingly evident that other alterations are required for the tumor to develop. Therefore, we set out to identify additional inheritable susceptibility markers and new potential preventive and therapeutic targets for retinoblastoma. We focused on the p16INK4A tumor suppressor gene because of its possible role in retinoblastoma pathogenesis and its involvement in predisposition to familial cancer. p16INK4A expression was analyzed in tumor samples from retinoblastoma patients by immunohistochemistry and in peripheral blood cells from both patients and their parents by real-time quantitative reverse transcription-PCR (qRT-PCR). Since promoter methylation is a common mechanism regulating p16INK4A expression, the methylation status of its promoter was also analyzed in blood samples from patients and their parents by methylation-specific PCR. A downregulation of p16INK4A was observed in 55% of retinoblastoma patients. Interestingly, in 56% of the cases showing p16INK4A downregulation at least one of the patients' parents bore the same alteration in blood cells. Analysis of p16INK4A promoter methylation showed hypermethylation in most patients with p16INK4A downregulation and in the parents with the same alteration in p16INK4A expression. The finding that p16INK4A was downregulated both in patients and their parents suggests that this alteration could be a novel inheritable susceptibility marker to retinoblastoma. The observation that p16INK4A downregulation seems to be due to its promoter hypermethylation opens the way for the development of new preventive and therapeutic strategies using demethylating agents.

Anterior diffuse retinoblastoma: mutational analysis and immunofluorescence staining.

Retinoblastoma is the most common primary intraocular tumor of childhood and may be heritable or occur sporadically. Anterior diffuse retinoblastoma is an uncommon variant that is thought to be sporadic. We describe a child with anterior diffuse retinoblastoma who presented with a pseudohypopyon. Genetic analysis showed a germline mutation of the RB1 allele that is potentially heritable. Immunofluorescence staining was positive for transforming growth factor beta and for vascular endothelial growth factor and negative for inducible nitric oxide synthase and for hypoxia inducible factor alpha in the tumor seeds, indicating acquisition of nonischemia-mediated survival factors of the tumor seeds in the aqueous humor.

Primary intraocular lymphoma: diagnosis and differential diagnosis.

Diagnosis of PIOL can be challenging. It requires a high degree of clinical suspicion and differential diagnosis includes infectious and non-infectious etiologies particularly the common masquaraders sarcoidosis, tuberculosis, viral retinitis and syphilis. The definitive diagnosis depends on demonstration of malignant lymphoma cells in ocular specimens or CSF. Ocular specimen could include vitreous, aqueous or chorioretinal biopsy. Ocular pathologist should be consulted prior to the diagnostic procedure to help handle and process the specimen appropriately. In addition to cytology, flow cytometry, immunohistochemistry, molecular analysis and cytokines may be used as adjuncts in facilitating the diagnosis.

Primary T-cell lymphoma of the retina and cerebellum: immunophenotypic and gene rearrangement confirmation.

PURPOSE: To document fully the first credible primary T-cell lymphoma of the retina and central nervous system in a 71-year-old man. DESIGN: Interventional, retrospective report. METHODS: Critical analysis of clinical history and findings, which included bilateral vitreitis with anterior chamber reaction, creamy intraretinal infiltrates, and retinal detachment; complete blood counts and other blood studies (anti-neutrophil cytoplasmic antibody [ANCA], angiotensin-converting enzyme levels, and Lyme and fluorescent treponemal antibody absorption titers); magnetic resonance imaging (MRI) scanning of the brain with total body computed tomographic and positron emission tomographic scanning; interleukin (IL) level determinations (IL-10 and IL-6); cytologic and electron microscopic evaluations; immunophenotyping of cells; and polymerase chain reaction studies for viral deoxyribonucleic acid and ribonucleic acid, and immunoglobulin heavy-chain, and T-cell receptor (TCR) gene rearrangements. RESULTS: The first vitreous specimen was diagnosed mistakenly as cytologically reactive and contained elevated levels of IL-10 and IL-6 in a ratio of 7 to 1. T cells predominated on immunophenotypic analysis. Computed tomographic and positron emission tomographic whole body scanning showed negative results for lymphoma. An MRI scan of the brain eventually revealed a cerebellar lesion. A retinal biopsy harbored cytologically atypical pleomorphic cells that were almost all immunophenotypically T cells; polymerase chain reaction studies demonstrated a clonal TCR gene rearrangement. T-cell lymphocytes in the biopsy specimen of the cerebellum had an identical clonal TCR gene rearrangement. CONCLUSIONS: This case unequivocally establishes that primary retinal T-cell lymphoma accompanied by central nervous system involvement can occur. Elevation in the IL-10 to IL-6 ratio in the face of inconclusive or confusing vitreous cytologic and immunophenotypic findings (a predominance of "reactive T cells with some atypicality") should lead to gene rearrangement studies on biopsies of involved tissues for the detection of T-cell clonality.

Phenotypic characterization of retinoblastoma for the presence of putative cancer stem-like cell markers by flow cytometry.

PURPOSE: Retinoblastoma (Rb) is an intraocular tumor that grows rapidly and poses a threat to sight and life. Similar to other tumors, there is increasing speculation that the Rb tumor also contains cancer stem-like cells that could influence the prognosis and response to therapy. This study was undertaken in an attempt to identify putative stem-like cells by characterizing different subpopulations of cells in retinoblastoma. METHODS: Freshly isolated tumor cells obtained from unfixed eye specimens (n=7) were analyzed for the presence of CD44, ABCG2, CXCR4, CD133, and CD90 using flow cytometry. RT-PCR was performed to analyze the expression of human Syntaxin1A, PROX1, CD133, and NSE in the sorted subpopulation of tumor cells. RESULTS: Two different subpopulations of cells were observed in seven samples. The small cells, assigned FSC(lo)/SSC(lo) (forward scatter low/side scatter low, ranging from 1.7% to 17.7%) were characterized as positive for CD44 and negative for CD133, CXCR4, and CD90. The large cells were designated as FSC(hi)/SSC(lo) (ranging from 2.7% to 35.1%) and characterized as positive for all markers. RT-PCR analysis revealed that sorted cells of FSC(lo)/SSC(lo) subpopulation expressed the retinal progenitor cell markers PROX1 and Syntaxin1A. CONCLUSIONS: Retinoblastoma, on flow cytometric analysis, revealed two distinct subpopulations with variable expression of stem cell and retinal progenitor markers. In these populations, the FSC(lo)/SSC(lo) subpopulation appeared to be more primitive, since they expressed stem cell (CD44) and retinal progenitor markers (PROX1 and Syntaxin 1A) combined with a relatively lower percentage of differentiated markers. Moreover, the FSC(hi)/SSC(lo) subpopulation showed a higher percentage of differentiated markers (CD90 and CD133).

Expression of motility-related protein MRP1/CD9, N-cadherin, E-cadherin, alpha-catenin and beta-catenin in retinoblastoma.

In our earlier study we showed that invasive retinoblastoma (RB) had down regulated tetraspanin protein KAI1/CD82, a family of cell surface glycoprotein. KAI1 may link to the cell surface molecules, such as integrins, E-cadherin, and other TM4SF members, and loss of KAI1 function may have a significant role in the progression of retinoblastoma. We also showed that epithelial cell adhesion molecule (EpCAM) is overexpressed in invasive RB. EpCAM expression decreases adhesion mediated by cadherins. Thus, we were further interested in studying the role of other adhesion molecules like cadherins and catenins in RB. We studied the expression of Motility-Related Protein 1 (MRP-1)/CD9, E-cadherin, N-cadherin, alpha-catenin and beta-catenin in RB and correlated clinicopathologically in 62 archival paraffin-embedded tumors by immunohistochemistry. There were 29 tumors with no invasion of choroids/optic nerve and 33 tumors with invasion of choroid/optic nerve/orbit. Western blotting was performed on 20 tumors using the same antibodies. We observed higher expression of CD9 (P<0.001), E-cadherin (P<0.001) and alpha-catenin (P<0.001) in the non-invasive RB and higher expression of N-cadherin (P<0.001) in invasive RB. The expression of beta-catenin was not significantly different between two groups of tumors. In Western blotting, we were able to see CD9 and E-cadherin expression in a minority of tumors while N-cadherin, alpha-catenin and beta-catenin were expressed with differing intensities in a majority of tumors. Thus, invasive tumors expressed increased N-cadherin, alpha-catenin and decreased E-cadherin and CD9. Thus, it appears that loss of E-cadherin and gain of N-cadherin expression are features of invasiveness. Further functional studies are required to evaluate the role of beta-catenin in RB.