Animal Models of Uveal Melanoma: Methods, Applicability, and Limitations.

Animal models serve as powerful tools for investigating the pathobiology of cancer, identifying relevant pathways, and developing novel therapeutic agents. They have facilitated rapid scientific progress in many tumor entities. However, for establishing a powerful animal model of uveal melanoma fundamental challenges remain. To date, no animal model offers specific genetic attributes as well as histologic, immunologic, and metastatic features of uveal melanoma. Syngeneic models with intraocular injection of cutaneous melanoma cells may suit best for investigating immunologic/tumor biology aspects. However, differences between cutaneous and uveal melanoma regarding genetics and metastasis remain problematic. Human xenograft models are widely used for evaluating novel therapeutics but require immunosuppression to allow tumor growth. New approaches aim to establish transgenic mouse models of spontaneous uveal melanoma which recently provided preliminary promising results. Each model provides certain benefits and may render them suitable for answering a respective scientific question. However, all existing models also exhibit relevant limitations which may have led to delayed research progress. Despite refined therapeutic options for the primary ocular tumor, patients' prognosis has not improved since the 1970s. Basic research needs to further focus on a refinement of a potent animal model which mimics uveal melanoma specific mechanisms of progression and metastasis. This review will summarise and interpret existing animal models of uveal melanoma including recent advances in the field.

Intravitreally Injected HCmel12 Melanoma Cells Serve as a Mouse Model of Tumor Biology of Intraocular Melanoma.

PURPOSE: To establish a mouse model with histologic characteristics of uveal melanoma for investigation of intraocular tumor biology of melanoma. METHODS: After injection of 1 × 10(5) of HCmel12 melanoma cells, a cutaneous melanoma cell line, into the vitreous of CX3CR1(+/GFP) or C57Bl/6 mice (n = 12), tumor growth patterns, clinicopathological features, angiogenesis and metastatic behavior were analyzed by histology (hematoxylin and eosin, periodic acid-Schiff without hematoxylin) and immunohistochemistry (HMB45/MART-1-Ab, F4/80-Ab, green fluorescent protein (GFP)-Ab and VE-cadherin-Ab). RESULTS: HCmel12 cells formed intraocularly growing tumor masses, which showed histologic features of intraocular melanoma such as angiotropism, intratumoral endothelial-lined vasculature, vasculogenic mimicry including prognostic significant extravascular matrix patterns, and invasion by inflammatory cells, in particular macrophages. There was no difference in tumor growth characteristics between CX3CR1(+/GFP) and C57Bl/6 mice. Five of 10 mice proceeded to extrascleral tumor growth and three of these developed metastases. CONCLUSIONS: Intraocularly injected HCmel12 cells developed tumor masses with histologic characteristics of aggressive melanoma similar to human uveal melanoma. Since hematogenous dissemination to the liver was not observed, intravitreally injected HCmel12 cells do not qualify as a model for metastasizing intraocular melanoma. However, since the eye represents a semi-closed compartment with access to constant blood supply, these intraocular tumors represent a model for studies of isolated parameters in general tumor biology of intraocular melanoma.

Distribution and presumed proliferation of macrophages in inflammatory diseases of the ocular adnexae.

PURPOSE: The aim of this article is to investigate whether macrophages show a proliferative activity (as indicated by Ki67 expression) and their distribution at the site of inflammation. MATERIALS AND METHODS: Six different macrophage-containing lesions from six different patients (four females, two males; age range: 16-58 years) were stained for macrophage markers (CD68, CD163) and Ki67 by immunohistochemistry. Immunofluorescence techniques were used to investigate dual-labeling of the specimens for CD68, CD163 and Ki67, respectively. RESULTS: With immunofluorescence staining, scattered cells in all specimens were dual-labeled for CD68-Ki67 and CD163-Ki67. All lesions were composed of mixed infiltrates of M1 (CD68+CD163-) and M2 (CD68+CD163+) macrophages. The center of epithelioid-cell granulomas and foreign body giant cells was exclusively composed of M1 macrophages. CONCLUSIONS: This study shows that CD68+ and CD163+ cells express Ki67, a marker for proliferative activity at the site of inflammation. Until recently, macrophages were regarded as end-differentiated cells without mitotic activity. Since self-renewal of M1 and M2 macrophages has been described in the literature, staining of macrophages with Ki67 may indicate proliferative activity or at least an activation state. The distribution of macrophages in classic granulomatous lesions with only M1 macrophages in the avascular center represents an immune response to foreign body material, whereas the proangiogenic M2 macrophages are located mostly in the surrounding inflammatory tissue and seem to be mandatory for the vascularization of the inflammatory tissue.

Anterior segment developmental anomalies in a 33-week-old fetus with MIDAS syndrome.

We report anterior segment abnormalities in both eyes of a 33-week-old fetus endorsing the diagnosis of MIDAS (microphthalmia, dermal aplasia, and sclerocornea) syndrome. After abortion, the fetus was examined by a standard pediatric autopsy that included macroscopic and microscopic examination of both eyes. Postmortem findings included craniofacial stigmata (such as hypertelorism, a flat nose and low-set ears) and an agenesis of the corpus callosum. Array comparative genomic hybridization revealed a deletion of the short arm of the X chromosome (region Xp22.2 to p22.32). Ophthalmopathologic examination of the eyes revealed microphthalmia with anterior segment developmental anomalies, in particular sclerocornea and Peters' anomaly, respectively. General pathology findings plus the ocular findings allowed the diagnosis of MIDAS syndrome. A discussion of differential diagnoses is provided. This case report indicates that ophthalmopathologic investigation of fetal eyes can be of great value for the further classification of syndromes.

Expression of the lymphatic marker podoplanin (D2-40) in human fetal eyes.

During human ocular development, expression of proteins varies in different maturation stages. This study aims to characterize structures in human fetal eyes stained by the lymphatic marker podoplanin (D2-40) with emphasis on the stage of maturation and the presence of intraocular lymphatic structures. Formalin-fixed paraffin-embedded eyes from 40 human fetuses between 10 and 38 weeks of gestation (WoG) were investigated. Immunohistochemical stains were performed for D2-40, LYVE-1 as a secondary lymphatic marker, and CD34 as a control for endothelial reactivity. A semiquantitative analysis of antigen expression in different segments of the eye was performed by light microscopy. The intensity of antigen expression was graded with a score ranging from 0 to 3. Podoplanin expression was found with a variable intensity in 97.5% of the eyes, in particular in lymphatic vessels of the conjunctiva (n = 26), conjunctival and corneal epithelium (n = 33), corneal endothelium (n = 4), trabecular meshwork (n = 28), and optic nerve sheaths (n = 23). A slight, equivocal staining reaction was noted in the choroid (n = 14). There was a correlation of antigen reactivity and the gestational age for corneal endothelial reactivity in earlier gestational stages (p = 0.003) and trabecular meshwork in older eyes (p = 0.031). D2-40 positive Müller cells were detected in two eyes ≥32 WoG. Thus, aside from conjunctival lymphatic vessels, podoplanin was expressed in several structures of the human fetal eye and the ocular adnexae at different gestational stages. Podoplanin positive structures were also found in the choroid and the chamber angle. However, lymphatic vessels or its progenitors could not be unequivocally identified in intraocular structures during 10-38 weeks of gestation. There is no evidence from our data that transient intraocular lymphactics develop in the fetal eye between 10 and 38 weeks of gestation.

Absence of lymphatic vessels in the developing human sclera.

The adult sclera is free of lymphatic vessels, but contains a net of blood vessels. Whether and when this selectively lymphangiogenic privilege is achieved during embryologic development is not known yet. Therefore, we investigated the developing human sclera for blood- and lymphatic vessels in 34 abortions/stillborns (12-38 weeks of gestation). The probes were subdivided into three groups (group 1: 12-18 weeks of gestation, n = 10; group 2: 19-23 weeks of gestation, n = 13; group 3: 24-38 weeks of gestation, n = 11), and prepared for paraffin sections followed by immunohistochemistry against CD31 to detect blood vessels, and against lymphatic vessel endothelial hyaluronan receptor-1 (LYVE1)/podoplanin to detect lymphatic vessels. We could show, that in the human episclera distinct CD31 + blood vessels are present as early as week of gestation 13. Their amount increased during pregnancy, whereas stromal CD31 + blood vessels were elevated in early pregnancy and regressed with ongoing pregnancy. In the lamina fusca CD31 + blood vessels were absent at any time point investigated. Single LYVE1 + cells were identified primarily in the episclera; their amount decreased significantly with increasing gestational ages (group 1 compared to group 3: p < 0.01). However, LYVE1+/podoplanin + lymphatic vessels were not detectable in the sclera at any gestational ages analyzed. In contrast to the conjunctiva where LYVE1+/podoplanin + lymphatic vessels were detectable as early as week 17, the amount of LYVE1 + cells in the sclera was highest in early pregnancy (group 1), with a significant decrease during continuing pregnancy (p < 0.001). These findings are the first evidence for a fetal lymphangiogenic privilege of the sclera and show, that the fetal human sclera contains CD31 + blood vessels, but is primarily alymphatic. Our findings suggest a strong expression of selectively antilymphangiogenic factors, making the developing sclera a potential model to discern antilymphangiogenic mechanisms.

Lens artifacts in human fetal eyes - the challenge of interpreting the histomorphology of human fetal lenses.

BACKGROUND: Evaluation of the lens, including cataractous changes, is often of paramount importance in the classification of fetal syndromes or forensic questions. On histology, the crystalline lens is - especially in fetal and infant eyes - an organ susceptible to numerous artifacts. Thus, the aim of our study was to study various factors (including fixatives) that might have an impact on lens histomorphology. METHODS: Twenty eyes from ten fetuses (formalin fixation: n = 10, glutaraldehyde fixation: n = 10), matched for gestational age and abortion (spontaneous vs. induced), were investigated macroscopically and by light microscopy. Sections were stained with routine hematoxylin & eosin (H&E), and periodic acid schiff (PAS). The age of the fetal eyes ranged from 15 to 36 weeks of gestation. Lens artifacts were analyzed and compared to fetal and adult lenses with definitive cataractous changes. In addition, 34 eyes from 27 fetuses with trisomy 21 were investigated for lens changes. RESULTS: All lenses showed artifacts of varying extent, in particular globules, vacuoles, clefts, anterior/posterior capsular separation, subcapsular proteinaceous material, fragmentation of the lens capsule/epithelium, and a posterior umbilication. Glutaraldehyde-fixed lenses displayed less artifacts compared to those fixed in formalin. Slight differences in the appearance of artifacts were found dependent on the fixative (formaldehyde vs glutaraldehyde) and the kind of abortion (iatrogenous vs spontaneous). The gestational age did not have a significant influence on the type and extent of lens artifacts. The lenses from fetuses with trisomy 21 displayed similar lens artifacts with no specific findings. CONCLUSIONS: Alterations in fetal lens morphology are extremely frequent and variable. These artifacts have to be carefully taken into account when interpreting post-mortem findings. Thus, the postmortem diagnosis of a fetal cataract should be made with great caution, and should include, in adherence to our proposed diagnostic flow diagram, the macroscopic lens assessment. Reference slides with a proven cataract are recommended for comparison in equivocal cases.

Vascular endothelial cadherin expression in lung specimens of patients with sepsis-induced acute respiratory distress syndrome and endothelial cell cultures.

AIMS: Vascular endothelial (VE) cadherin is a cell adhesion molecule localized at endothelial cell (EC) junctions. As a major component of endothelial adherens junctions, its main function is the maintenance and regulation of EC integrity. In the acute respiratory distress syndrome (ARDS), increased vascular permeability is a major mechanism in pulmonary edema and lung dysfunction. In this study, VE-cadherin expression was investigated in ARDS lungs and control tissue as well as in an ARDS cell culture model. METHODS: Lung specimens of patients with ARDS due to Gram-negative sepsis (n = 20; control lung tissue: n = 41) and cell cultures of human pulmonary microvascular ECs and human umbilical vein ECs stimulated with LPS, TNF-α and IFN-γ were stained with a VE-cadherin antibody. Staining intensity was semiquantitatively evaluated by conventional light and immunofluorescence microscopy. RESULTS: VE-cadherin expression was statistically significantly reduced in the endothelium of all vessel types in ARDS lungs compared to control tissue. Cell cultures showing disrupted cellular borders confirmed these results. CONCLUSION: Reduced expression of VE-cadherin has to be considered as a major mechanism of increased vessel permeability in ARDS. The previously described vessel-type-specific expression pattern of VE-cadherin in the human lung is not influenced by ARDS.

Morphological and immunohistochemical changes after corneal cross-linking.

PURPOSE: To present light and electron microscopic as well as immunohistochemical findings after corneal cross-linking (CXL). METHODS: Six keratoconus corneas after CXL, 12 keratoconus corneas without CXL, and 7 normal corneas were examined by light microscopy, indirect immunohistochemistry using antibodies against proapoptotic BAX, antiapoptotic survivin, and BCL-2, and anti-smooth muscle actin and, in part, by transmission electron microscopy. Direct immunofluorescence with 4'6-diamidino-2-phenylindole was performed to analyze keratocytes/area in the anterior, middle, posterior, peripheral, and central corneal stroma. RESULTS: The period between CXL and keratoplasty ranged from 5 to 30 months. All keratoconus corneas showed the typical histological changes. Increased proapoptotic BAX expression and/or antiapoptotic survivin expression were noticed in keratocytes and endothelium in 2 keratoconus specimens after CXL. Smooth muscle actin was only observed in subepithelial scar tissue of 2 keratoconus corneas without CXL. Keratoconus corneas after CXL revealed a significant reduction in keratocyte counts in the entire cornea (P = 0.003) compared with keratoconus corneas without CXL and normal corneas. This difference was because of a loss of keratocytes in the anterior (P = 0.014) and middle (P = 0.024) corneal stroma. Keratocytes in CXL corneas were reduced in the center (P = 0.028) and the periphery (P = 0.047). CONCLUSIONS: CXL in human keratoconus can cause considerable morphologic corneal changes up to 30 months postoperatively. Especially noteworthy is a long-lasting, maybe permanent, keratocyte loss in the anterior and middle corneal stroma involving the central and peripheral cornea. As long-term corneal damage after CXL is of genuine concern, particular care should be taken to perform this procedure only in accordance with investigational protocols.

M2/M1 ratio of tumor associated macrophages and PPAR-gamma expression in uveal melanomas with class 1 and class 2 molecular profiles.

Macrophages have been found to be negative predictors of outcome in patients with uveal melanoma. In particular, recent studies point toward a disease-progressing role of proangiogenic M2 macrophages in melanomas with monosomy 3. Although most studies implicate a protective effect of PPAR-gamma activation in tumors, PPAR-gamma has also been shown to promote the polarization of M1 macrophages toward the M2 phenotype. The purpose of this investigation was first, to characterize the phenotype of tumor infiltrating macrophages and second, to study PPAR-gamma expression in uveal melanomas with molecular gene expression profile as prognostic predictors for patients' outcome. Twenty specimens from patients with uveal melanoma were analyzed for clinical and histologic tumor characteristics. The molecular RNA profile (class 1 or class 2) was commercially determined. Using immunohistochemical techniques, the specimens were dual labeled for CD68 and CD163. CD68 + CD163- M1 macrophages and CD68 + CD163+ M2 macrophages were analyzed in ten high power fields sparing macrophage-poor areas and a mean value was calculated for each tumor. The tumors were immunostained for von Willebrand factor and the micro vascular density (MVD) was analyzed according to Foss. To assess the proliferative rate of each tumor, Ki67 expression was evaluated in ten high power fields followed by calculation of a mean value. Expression of PPAR-gamma was evaluated using a score from 0 (no staining) to 3 (tumor entirely stained). Statistical analysis and a respective correlation were made between histologic characteristics, molecular profile, type of tumor infiltrating macrophages (M1 vs. M2), MVD, proliferative rate, and PPAR-gamma expression. Our results showed a correlation between the ratio of M2/M1 macrophages and the molecular profile with a ratio of approximately 1 corresponding to molecular class 1 and a ratio of approximately 2 corresponding to molecular class 2 (p = 0.01). The ratio of M2/M1 macrophages was higher in tumors with extraocular extension (p = 0.01). PPAR-gamma was predominantly expressed in the cytoplasm of tumor cells. Its expression showed no association with the molecular RNA profile (p = 0.83). This study confirmed that the ratio of M2/M1 macrophages is another prognostic factor in uveal melanoma. Thus, polarization of macrophages plays an important role for patients' outcome. PPAR-gamma is expressed in uveal melanoma tumor cells and further studies are warranted to determine its role in tumor biology.

Immunolocalization of different collagens in the cornea of human fetal eyes: a developmental approach.

PURPOSE: To study the corneal development in the human fetal eye with particular emphasis on the epithelial basement membrane and Bowman's layer. Thus, immunohistochemical markers supposed to stain this region were employed. MATERIAL AND METHODS: 19 formalin-fixed fetal eyes and a 16-day-old newborn's cornea without any obvious irregularities of the anterior segment were investigated. The age of the fetal eyes ranged from 11 to 38 week of gestation (WoG). The eyes (including the corneal thickness) were measured and, in addition to routine hematoxylin and eosin (H&E) and periodic acid-Schiff (PAS) stains, immunohistochemical labeling with antibodies to collagen IV, V, IX, and XVII was performed. RESULTS: Analysis of the H&E stains revealed that measurements of corneal thickness correlated well with corneal development as a basic indicator for maturation. In a more detailed immunohistochemical analysis, collagen IV was expressed in the epithelial basement membrane (BM) of the cornea, conjunctiva, and Descemet's membrane in fetal eyes up to the age of 23 WoG. In fetal eyes older than 23 WoG, staining was confined to the limbal area only. With the antibody against collagen V, the corneal stroma and the BM were intensely stained. Bowman's layer (first detected at 17 WoG by light microscopy) was not labeled. Anti-collagen IX labeled predominantly the conjunctival and corneal epithelium. With anti-collagen XVII, the BM of the cornea and conjunctiva was stained in all fetal eyes, whereas intracellular expression in the epithelium increased with age. CONCLUSION: Our results indicate maturation-associated variations of collagen expression in the human cornea. Measurements of the corneal thickness may serve as an additional parameter to narrow down the developmental age with possible implications for pediatric pathology and forensic issues.

Langerhans cell histiocytosis of the orbit: five clinicopathologic cases and review of the literature.

Langerhans cell histiocytosis (LCH) is a proliferation of Langerhans cells intermixed with inflammatory cells, in particular eosinophils, that may manifest as unisystem (unifocal or multifocal) or multisystem disease. Orbital involvement typically manifests as a solitary lesion that carries a favorable prognosis. We describe the clinical and histologic spectrum of LCH of the orbit in our five cases. One patient exhibited multifocal unisystem disease; the other four had a localized process. Typical histologic features included numerous histiocytes with varying degrees of giant cell formation and scattered eosinophilic granulocytes. The presence of Langerhans cells was confirmed by CD1a and S100 immunohistochemistry. Transmission electron microscopy demonstrated characteristic intracytoplasmic Birbeck granules. We review the different ophthalmic manifestations of LCH and treatment strategies. As LCH may solely involve the orbit, treatment is based on the degree of organ involvement. LCH should included in the differential diagnosis in tumors of the ocular adnexae, especially in young children.

Reactive retinal astrocytic tumors (so-called vasoproliferative tumors): histopathologic, immunohistochemical, and genetic studies of four cases.

PURPOSE: To evaluate the cellular nature of and diagnostic terminology used in connection with acquired retinal "vasoproliferative tumors." DESIGN: Retrospective clinicopathologic study. METHODS: Clinical records and microscopic slides of 4 enucleated globes were reviewed. Special stains and immunohistochemical probes for CD31, CD34, p53, glial fibrillary acidic protein (GFAP), CD163, and Ki67 (cell replication) were employed; ultrastructural and fluorescence in situ hybridization (FISH) analyses were performed. RESULTS: Tumors were located inferotemporally in middle-aged patients. They were uniformly composed of compacted elongated, GFAP-positive spindle cells (due to intermediate filaments identified ultrastructurally) with a Ki67 index of less than 1%. Rosenthal fibers and eosinophilic granular bodies were observed. Hyalinized periodic acid-Schiff-positive vessels were widely separated. CD31 and CD34 revealed a sparse microvasculature. Tumor-associated exudate spread predominantly subretinally. The retinal pigment epithelium had undergone extensive placoid fibrous metaplasia with focal ossification. P53 upregulation, BRAF-KIAA gene rearrangement, and IDH1R132H mutation typically associated with low-grade astrocytic neoplasms were absent. CONCLUSIONS: Retinal "vasoproliferative" tumors have been mischaracterized, because they actually display a paucity of microvessels. Proliferating fibrous astrocytes with a very low proliferation index predominate, without immunohistochemical or genetic evidence favoring a neoplasm. Subretinal exudate appeared capable of provoking widespread fibrous metaplasia of the pigment epithelium that was mainly responsible for secondary retinal damage. The term "reactive retinal astrocytic tumor" is proposed as more appropriate for this entity. In carefully selected progressive lesions, consideration should be given to earlier surgical intervention before extensive subretinal exudate accumulates and pigment epithelial proliferation with fibrous metaplasia ensues.

Pigmented tumour of the eyelid with unexpected findings.

A 63-year-old patient presented with a small painless nodular tumour of his left lower eyelid which had increased in size over the last few weeks. The tumour was excised by wedge resection and submitted for ophthalmopathologic examination. Histopathologic examination revealed a cystic lesion of apocrine origin with focal proliferations. The proliferative cells appeared pleomorphic and displayed marked atypia. Staining with Ki67 revealed a significant mitotic activity supporting the diagnosis of an apocrine adenocarcinoma of Moll. As the lesion displayed in most parts characteristics of a benign apocrine hidrocystoma, a thorough and critical histopathological examination is required in such cases to avoid missing an early malignant transformation.

Diffuse large B-cell lymphoma of the orbit: clinicopathologic, immunohistochemical, and prognostic features of 20 cases.

PURPOSE: To evaluate a series of orbital diffuse large B-cell lymphomas (DLBCL) for prognostic features and therapeutic outcomes. DESIGN: Retrospective multicenter case study of clinical and immunohistochemical features of 20 patients. METHODS: Clinical, histopathologic, and immunohistochemical features were correlated with outcomes. Immunohistochemistry for biomarkers including Bcl-6, CD5, CD10, CD20, FOXP1, GCET1, and MUM1 was performed to differentiate between 2 major genetic subtypes of DLBCL: activated B-cell-like (ABC) and germinal center B-cell-like (GCB). RESULTS: Sixteen patients presented with unilateral and 4 with bilateral tumors. Three had bony erosion of the orbit on imaging studies. Of 14 patients with detailed follow-ups, 3 had a prior or concurrent lymphomatous disease; 8 had stage I disease (limited to the orbit) at presentation; and 3 were newly diagnosed with systemic (stage IV) DLBCL. Localized disease was treated with combined systemic chemotherapy, including rituximab and radiation with no deaths to date; there was 1 death related to systemic DLBCL. Clinical staging was the best predictive method and no immunohistochemical feature or subcategory (ABC vs GCB) correlated with outcome. CONCLUSIONS: Primary orbital DLBCL has a more favorable prognosis than systemic DLBCL and may arise from a preexistent hematolymphomatous neoplasm (4 out of 20 cases). In our series, orbital DLBCL had a 57% likelihood of being restricted to the ocular adnexa. Clinical staging was more helpful in predicting outcome than any single immunohistopathologic feature or combination of biomarkers. Orbital radiation of 30 gray in conjunction with systemic chemotherapy with rituximab can achieve disease-specific survival approaching 100% in purely localized cases.

Conjunctival stromal tumor: report of 4 cases.

PURPOSE: To describe the clinical, histopathologic, immunohistochemical, and ultrastructural features of a case series of benign stromal tumors in the bulbar conjunctiva. DESIGN: Observational case series. PARTICIPANTS: Four patients with a conjunctival lesion that were classified histologically as low-grade stromal tumors consisting of spindle-shaped cells with occasional pseudonuclear inclusion and multinucleated cells in a partly myxoid matrix. METHODS: Four cases of low-grade conjunctival stromal tumors were retrospectively identified in an ophthalmic pathology laboratory database. Patients' records were analyzed for demographic data, clinical appearance, and the postoperative course. Formalin-fixed, paraffin-embedded specimens were routinely processed and stained with hematoxylin and eosin and periodic acid Schiff. Immunohistochemical stains for vimentin, S100, CD34, smooth muscle actin (SMA), CD68, and factor XIIIa were performed. Transmission electron microscopy (TEM) was performed on 3 of the cases. MAIN OUTCOME MEASURES: Histopathologic evaluation (including immunostains and TEM) and clinical correlation. RESULTS: All 4 tumors occurred in the bulbar conjunctiva of patients between 41 to 53 years of age. None of the patients developed recurrence after excisional biopsy. Histologically, all tumors exhibited spindle-shaped cells with pseudonuclear inclusions and occasional multinuclear cells. Mitotic figures were not observed. The stroma seemed to be myxoid to collagenous. Immunohistochemical stains were positive for CD34, vimentin, and focally for CD68, but were negative for S100 and SMA. CONCLUSIONS: We propose to classify these benign lesions, which share distinct histopathologic features, as "conjunctival stromal tumors." A reactive/inflammatory component needs to be considered in the pathogenesis of this lesion.