Neuropeptide Y receptor 1 is expressed by B and T lymphocytes and mast cells in infantile haemangiomas.

AIM: We investigated the expression of neuropeptide Y (NPY), NPY receptor 1 (NPYR1) and NPY receptor 2 (NPYR2) in infantile haemangiomas (IHs). METHODS: Immunohistochemical (IHC) staining was performed on proliferating IHs from six patients aged 4-13 (mean 8.7) months and involuted IHs from six patients aged 5-59 (mean 18.7) years, for the expression of NPY, NPYR1 and NPYR2. Protein and messenger ribonucleic acid expression corresponding to these proteins was investigated by Western blotting and NanoString analysis, respectively. RESULTS: IHC staining, Western blotting and NanoString analysis demonstrated the presence of NPYR1, but not NPYR2, within proliferating and involuted IHs. IHC staining showed NPYR1 was expressed by B and T lymphocytes expressing CD45 and mast cells expressing tryptase. IHC staining demonstrated the presence of NPY on the NPYR1+ cells, but it was not detected by Western blotting or NanoString analysis. CONCLUSION: NPYR1, but not NPYR2, was present in IHs. The localisation of NPYR1 to B and T lymphocytes and mast cells suggests its role in the biology of IHs. The demonstration of NPY on the NPYR1+ cells, without active transcription, suggests that NPY was not being produced within IHs.

[13 cases of littoral cell angioma in spleens].

OBJECTIVE: To investigate the clinicopathological features, morphological characteristics, immunophenotypes of littoral cell angioma (LCA) in spleen, and to provide new evidence for making diagnosis and avoiding misdiagnosis. METHODS: Clinicopathological data, histological characteristics of 13 cases of LCA were retrospectively studied and immunohistochemical staining was imposed on the paraffi-nembedded specimens, and 5 cases of cavernous hemangioma, 4 cases of normal littoral cells of spleens were used as control groups, simultaneously. RESULTS: All the 13 LCA patients included 7 males and 6 females, aged from 39 to 70 years with an average of 54. 2 years and a median age of 55 years. Among these tumor patients, 6 cases were accompanied by malignances, benign tumors or inflammation states at abdominal cavities, and 7 cases were accidentally discovered by physical examinations. Grossly, spleens contained solitary or multiple gray red nodules ,which ranged from 0.5 to 6.2 cm in diameter. Histologically, tumors were composed by anastomosing vascular spaces which were lining by plump, rounded to cuboidal littoral cells that extended into vascular lumens. Usually, papillary frameworks that were covered by these cells were also seen extending into the lumens in some areas. Other types of histiocytoid cells were identified in lumens and the sizes were larger than the littoral cells. Both types of cells absented cytologic atypia. Immunohistochemical study demonstrated that the littoral cells in all cases were positive for vascular endothelial and histiocyte markers, such as CD21, CD31, CD68, polyclone FVIII RAg and ERG, while these cells were negative for CD8, CD34, and WT-1. These findings manifested that immunophenotype of littoral cell in LCA distinctive from that in controls. CONCLUSION: LCA is a benign lesion, which frequently occurs in the elderly. Its etiology remains confusion, however, immune dysregulation may associate with it because of the concomitance with other tumor or inflammation in some cases. The littoral cells in LCA show a hybrid endothelial-histiocytic phenotype on immunohistochemistry, therefore these cells may have features that intermediate between those of endotheliocytes and histiocytes. Emphasizing the histological findings and immunophenotypes is significant for diagnosis and differential diagnosis.

A hydrogel-endothelial cell implant mimics infantile hemangioma: modulation by survivin and the Hippo pathway.

Microvascular endothelial cells cultured in three-dimensional hydrogel scaffolds form a network of microvessel structures when implanted subcutaneously in mice, inosculate with host vessels, and over time remodel into large ectatic vascular structures resembling hemangiomas. When compared with infantile hemangiomas, similarities were noted, including a temporal progression from a morphological appearance of a proliferative phase to the appearance of an involuted phase, mimicking the proliferative and involutional phases of infantile hemangioma. Consistent with the progression of a proliferative phase to an involuted phase, both the murine implants and human biopsy tissue exhibit reduced expression of Ajuba, YAP, and Survivin labeling as they progressed over time. Significant numbers of CD45+, CD11b+, Mac3+ mononuclear cells were found at the 2-week time point in our implant model that correlated with the presence of CD45+, CD68+ mononuclear cells observed in biopsies of human proliferative-phase hemangiomas. At the 4-week time point in our implant model, only small numbers of CD45+ cells were detected, which again correlated with our findings of significantly diminished CD45+, CD68+ mononuclear cells in human involutional-phase hemangiomas. The demonstration of mononuclear cell infiltration transiently in the proliferative phase of these lesions suggests that the vascular proliferation and/or regression may be driven in part by an immune response. Gross and microscopic morphological appearances of human proliferative and involutional hemangiomas and our implant model correlate well with each other as do the expression levels of Hippo pathway components (Ajuba and YAP) and Survivin and correlate with proliferation in these entities. Inhibitors of Survivin and Ajuba (which we have demonstrated to inhibit proliferation and increase apoptosis in murine hemangioendothelioma cell tissue culture) may have potential as other beneficial treatments for proliferating infantile hemangiomas. This implant model may have potential as a modest through-put screen for testing and development of therapeutics targeted at the proliferative phase of infantile hemangiomas, reducing the subsequent postinvolutional scarring or deformities sometimes associated with these lesions.

Thrombin receptor PAR-1 activation on endothelial progenitor cells enhances chemotaxis-associated genes expression and leukocyte recruitment by a COX-2-dependent mechanism.

BACKGROUND: Endothelial colony forming cells (ECFC) represent a subpopulation of endothelial progenitor cells involved in endothelial repair. The activation of procoagulant mechanisms associated with the vascular wall's inflammatory responses to injury plays a crucial role in the induction and progression of atherosclerosis. However, little is known about ECFC proinflammatory potential. AIMS: To explore the role of the thrombin receptor PAR-1 proinflammatory effects on ECFC chemotaxis/recruitment capacity. METHODS AND RESULTS: The expression of 30 genes known to be associated with inflammation and chemotaxis was quantified in ECFC by real-time qPCR. PAR-1 activation with the SFLLRN peptide (PAR-1-ap) resulted in a significant increase in nine chemotaxis-associated genes expression, including CCL2 and CCL3 whose receptors are present on ECFC. Furthermore, COX-2 expression was found to be dramatically up-regulated consequently to PAR-1 activation. COX-2 silencing with the specific COX-2-siRNA also triggered down-regulation of the nine target genes. Conditioned media (c.m.) from control-siRNA- and COX-2-siRNA-transfected ECFC, stimulated or not with PAR-1-ap, were produced and tested on ECFC capacity to recruit leukocytes in vitro as well in the muscle of ischemic hindlimb in a preclinical model. The capacity of the c.m. from ECFC stimulated with PAR-1-ap to recruit leukocytes was abrogated when COX-2 gene expression was silenced in vitro (in terms of U937 cells migration and adhesion to endothelial cells) as well as in vivo. Finally, the postnatal vasculogenic stem cell derived from infantile hemangioma tumor (HemSC) incubated with PAR-1-ap increased leukocyte recruitment in Matrigel(®) implant. CONCLUSIONS: PAR-1 activation in ECFC increases chemotactic gene expression and leukocyte recruitment at ischemic sites through a COX-2-dependent mechanism.

Evaluation of expression profiles of hematopoietic stem cell, endothelial cell, and myeloid cell antigens in spontaneous and chemically induced hemangiosarcomas and hemangiomas in mice.

It is unclear whether the process of spontaneous and chemically induced hemangiosarcoma and hemangioma formation in mice involves the transformation of differentiated endothelial cells (ECs) or recruitment of multipotential bone marrow-derived hematopoietic stem cells or endothelial progenitor cells (EPCs), which show some degree of endothelial differentiation. In the present study, immunohistochemical staining for hematopoietic stem cell markers (CD45 and CD34), EC markers (vascular endothelial growth factor receptor 2 [VEGFR2], CD31, and factor VIII-related antigen), and a myeloid lineage marker (CD14) was employed to better define the origin of hemangiosarcomas and hemangiomas in mice. Staining was negative for CD45, factor VIII-related antigen, and CD14 and positive for CD34, VEGFR2, and CD31, indicating that mouse hemangiosarcomas and hemangiomas are composed of cells derived from EPCs expressing CD34, VEGFR2, and CD31 but not factor VIII-related antigen. The lack of CD45 expression suggests that mouse vascular tumors may arise from EPCs that are at a stage later than hematopoietic stem cells. Since factor VIII-related antigen expression is known to occur later than CD31 expression in EPCs, our observations may indicate that these tumor cells are arrested at a stage prior to complete differentiation.  In addition, myeloid lineage cells do not appear to contribute to hemangiosarcoma and hemangioma formation in mice.

Microvenular hemangioma presenting with numerous bilateral macules, patches, and plaques: a case report and review of the literature.

Microvenular hemangioma (MVH) is a rare, slowly growing, benign vascular tumor that typically presents as a solitary enlarging plaque or nodule on the trunk or the extremities of young to middle-aged adults. A minority of MVH present with multiple lesions that are either gradually or suddenly acquired (eruptive MVH). Herein, we report a case of a 53-year-old woman who progressively developed numerous bilateral MVHs presenting as enlarging, blanching, erythematous to violaceous macules, patches, and plaques over the proximal thighs and axillae. Two biopsies exhibited the irregular branching venules with inconspicuous lumina lacking endothelial atypia and associated with dermal fibrosis characteristic of MVH. Immunophenotypically, the endothelium expressed Wilms Tumor 1, CD31, CD34, and erythrocyte-type glucose transporter protein (GLUT-1) GLUT-1 focally and was negative for Human herpes virus 8 and the lymphatic marker D2-40. In addition, numerous dermal spindle cells expressing CD34 and procollagen, putative fibrocytes, surrounded the thickened dermal collagen bundles and small vessels of MVH implicating a reactive/reparative (proliferative) process due to an unrecognized cutaneous injury. A review of MVH summarizing its clinicopathologic findings and its natural history is presented.

Urea immunoliposome inhibits human vascular endothelial cell proliferation for hemangioma treatment.

BACKGROUND: Urea injection has been used in hemangioma treatment as sclerotherapy. It shrinks vascular endothelial cells and induces degeneration, necrosis, and fibrosis. However, this treatment still has disadvantages, such as lacking targeting and difficulty in controlling the urea dosage. Thus, we designed a urea immunoliposome to improve the efficiency of treatment. METHODS: The urea liposome was prepared by reverse phase evaporation. Furthermore, the urea immunoliposome was generated by coupling the urea liposome with a vascular endothelial growth factor receptor (VEGFR) monoclonal antibody using the glutaraldehyde cross-linking method. The influence of the urea immunoliposome on cultured human hemangioma vascular endothelial cells was observed preliminarily. RESULTS: Urea immunoliposomes showed typical liposome morphology under a transmission electron microscope, with an encapsulation percentage of 54.4% and a coupling rate of 36.84% for anti-VEGFR. Treatment with the urea immunoliposome significantly inhibited the proliferation of hemangioma vascular endothelial cells (HVECs) in a time- and dose-dependent manner. CONCLUSIONS: The urea immunoliposome that we developed distinctly and persistently inhibited the proliferation of HVECs and is expected to be used in clinical hemangioma treatment.

Littoral cell angioma of the spleen in a patient with previous pulmonary sarcoidosis: a TNF-α related pathogenesis?

BACKGROUND: Littoral cell angioma (LCA) is a rare vascular tumor of the spleen. Generally thought to be benign, additional cases of LCA with malignant features have been described. Thus, its malignant potential seems to vary and must be considered uncertain. The etiology remains unclear, but an immune dysregulation for the apparent association with malignancies of visceral organs or immune-mediated diseases has been proposed. CASE PRESENTATION: We report a case of LCA in a 43-year old male patient who presented with a loss of appetite and intermittent upper abdominal pain. Computed tomography showed multiple hypoattenuating splenic lesions which were hyperechogenic on abdominal ultrasound. Lymphoma was presumed and splenectomy was performed. Pathological evaluation revealed LCA. CONCLUSIONS: LCA is a rare, primary vascular neoplasm of the spleen that might etiologically be associated with immune dysregulation. In addition, it shows a striking association with synchronous or prior malignancies. With about one-third of the reported cases to date being co-existent with malignancies of visceral organs or immune-mediated diseases, this advocates for close follow-ups in all patients diagnosed with LCA. To our knowledge, this report is the first one of LCA associated with previous pulmonary sarcoidosis and hypothesizes a TNF-α related pathogenesis of this splenic tumor.

[Progressive increase of serum circulating immune complexes and its significance in patients during the progression from chronic hepatitis B to hepatocellular carcinoma].

OBJECTIVE: To investigate the significance of increasing circulating immune complex (CIC) in patients during the progression from chronic hepatitis B to hepatocellular carcinoma (HCC). METHODS: Serum levels of CIC from 20 hospitalized patients diagnosed by pathology with primary HCC, and 13 with hepatic hemangioma, and from 45 subjects with chronic HBV infection who finally developed into HCC (45 cases), and age- and gender-matched 45 subjects who kept the chronic HBV infection after consecutively followed up for 10 - 13 years by June of 2009 were quantified by ELISA. The serum levels of anti liver-kidney microsomal (anti LKM-1) antibodies were also measured by ELISA, and that of HBV-DNA were quantified by Taqman probe-based real time PCR in the followed up chronic HBV infection subjects. In the 45 chronic HBV subjects who finally developed into HCC and the 45 controls, serum samples were collected and determined at 3 time points: the baseline when the subjects were recruited, the middle point during the follow-up, and the end of follow-up. RESULTS: The serum level of CIC was significantly higher in the 20 HCC patients than that in the 13 hemangioma cases (P < 0.001). When HCC was diagnosed, the CIC concentration was significantly higher than that in the baselines (P < 0.001) in the 45 chronic HBV subjects who finally developed into HCC after the consecutively follow-up for 5 - 13 years. Of them, 36 patients (80.0%) showed progressively increased CIC during the follow-up (P < 0.001). In the controls, the CIC levels were kept relatively stable during the follow-up. Among them, 17 patients (37.8%) showed CIC slightly increased (P = 0.046). Kaplan-Meier survival analysis indicated that elevated serum CIC during the follow-up increased cumulative HCC incidence (HR = 2.77, 95%CI 1.47 - 5.22). In addition, the serum levels of anti-LKM-1 and HBV-DNA were also significantly higher in the patients who finally progressed into HCC than that in the controls and maintained at a high level during the follow-up tested at all the 3 time points. Further analysis indicated that the serum level of CIC was correlated with that of serum HBV-DNA only when HCC was diagnosed (r = 0.344, P = 0.026). CONCLUSION: Progressive increase of serum CIC level may be one of risk factors reflecting HCC development from chronic HBV infection.

Severe gastrointestinal bleeding and thrombocytopenia in a child with an anti-GATA1 autoantibody.

We describe a patient, who developed during the first week of life petechiae and hematomas caused by severe thrombocytopenia and gastrointestinal bleeding due to multiple small gastric hemangiomata. Bone marrow examination showed hypermegakaryocytosis and dysmegakaryopoiesis. Alloimmune thrombocytopenia was excluded. Only 3 y later, platelet counts normalized and bleedings disappeared but small skin hemangiomata remained. Electron microscopy showed enlarged round platelets with a paucity of alpha granules similar as in GATA1-deficient patients but no GATA1 mutation was found. Immunoblot analysis showed a strong interaction between patient Igs and recombinant GATA1, GATA2, and the N finger (Nf) of GATA1. The lymphocyte transformation test with recombinant GATA1Nf was positive. In vitro culturing of normal CD34 cells with purified patient Igs showed a decreased number of megakaryocyte colonies but an increased overall size of the colonies compared with control Igs. Mice injected with patient Igs showed a reduced platelet count compared with mice injected with control Igs. Thrombopoiesis was also reduced after injection of patient Igs in transgenic zebrafish compared with control Igs. In conclusion, this study is the first report of an anti-GATA1 autoantibody leading to severe thrombocytopenia and gastrointestinal bleeding from multiple pinpoint hemangiomata.

Intralymphatic atypical T-cell proliferation in a cutaneous hemangioma.

We report an unusual case of atypical T-cell proliferation involving the lymphatic vessels within a cutaneous hemangioma from an elderly woman. Despite the blastic morphology, the CD4 restricted phenotype and the very high proliferation index, the clinical presentation (single skin lesion in a healthy woman), the benign clinical course and the absence of T-cell receptor (TCR) clonal rearrangement favored a reactive nature of the process. Since the atypical cells showed an effector/memory-like regulatory T-phenotype (CD45RO+, CD25+ and FOXp3+), expressed the migration-associated molecule CCR7 and were exclusively located within podoplanin+ lymphatic vessels, we speculate that the process might reflect an unusual local immune response, with migration of T-cells to draining lymph nodes.

Eruptive microvenular hemangiomas in 4 Chinese patients: clinicopathologic correlation and review of the literature.

Microvenular hemangioma (MVH) is an uncommon benign vascular neoplasm that usually occurs as a solitary asymptomatic red or purple papule, nodule, or plaque with a predilection for the upper extremities. Patients with more than 1 lesion, that is, multiple MVHs, are extremely rare. We describe the clinicopathologic features of 4 Chinese patients who had a rapidly progressive abrupt onset of numerous MVHs numbering in the tens to hundreds. Clinically, the correct diagnosis of MVH could not be made in any of our patients; however, histologic examination revealed the characteristic features of MVH. Immunohistochemical stains were performed in all cases and showed the vessel lining cells to be positive for CD34, CD31, and factor VIII-related antigen. Polymerase chain reaction for human herpesvirus-8 was negative in all cases. The differential diagnosis and review of the literature of patients with multiple MVHs are presented.

Expression of allograft inflammatory factor-1 and CD68 in haemangioma: implication in the progression of haemangioma.

BACKGROUND: Recent studies revealed that immune and immune-mediated inflammatory events may contribute to the pathogenesis of haemangioma. As a modulator of immune responses, the allograft inflammatory factor-1 (AIF-1) is involved in immune dysfunction and macrophage activation. OBJECTIVE: To investigate the possible role of AIF-1 in the progression of haemangioma. METHODS: In a retrospective study of haemangiomas in the oral and facial regions, we assessed lesional immunoreactivities for AIF-1, CD68 and Ki67. Negative controls were similarly confirmed, including 24 pyogenic granulomas, 26 vascular malformations, five samples of normal skin, 10 squamous cell carcinomas of the tongue and three placentas. Immunostaining for each antigen in the haemangiomas was compared with control tissues. RESULTS: Out of all the samples, intense immunoreactivity for AIF-1 was detected in 17 of 19 (89%) haemangioma specimens, with a specific location in the endothelial cells. The intensity of AIF-1 immunostaining did not show remarkable difference among proliferating, involuting and involuted haemangiomas. CD68-positive endothelial cells were found in the neovessels of haemangiomas, as well as in pyogenic granulomas and squamous cell carcinoma. CONCLUSIONS: The exclusive expression of AIF-1 on endothelial cells of haemangiomas suggests that it may play a significant role in the pathophysiology and progression of haemangiomas. AIF-1 can be used as an additional biomarker for infantile haemangiomas. CD68-positive cells participate in the neovessel formation during proliferative haemangioma and contribute to the promotion of haemangioma growth.

Cutaneous epithelioid angiomatous nodule: a report of a series including a case with moderate cytologic atypia and immunosuppression.

BACKGROUND: Cutaneous epithelioid angiomatous nodule (CEAN) is a very rare and relatively recently recognized vascular proliferation characterized usually by minimal cytological atypia and accompanying mitotic activity. As such, CEAN represents an important diagnostic pitfall, which could lead to significant misdiagnosis and unnecessary treatment. METHODS: The clinicopathologic findings of 5 cases of CEAN were reviewed including a unique case with typical findings but also moderate cytologic atypia and brisk mitotic activity in a patient on immunosuppression. RESULTS: The cases were in 3 women and 2 men ranging in age from 18 to 61 years with lesions in the neck (2 cases), upper arm, back and shoulder. In 4 of the cases, the patients did not have any relevant potentially contributory clinical history, and in 1 case the patient was on immunosuppressive treatment. All 5 cases were superficially located within the dermis, well-circumscribed and similarly composed of epithelioid cells displaying minimal (in 4 cases) and moderate (1 case) atypia. The mitotic count ranged from 1 to 3 per 10 high power fields (HPF) in 4 cases and up to 9 per 10 HPF in the immunosuppressed patient. Atypical mitoses were not encountered in any of the cases. Two lesions that were incompletely excised recurred, but none of the patients showed distant metastases. CONCLUSION: While cytologically alarming, CEAN has a characteristic microscopic appearance and if completely excised follows an indolent course.

Glomeruloid hemangioma associated with TAFRO syndrome.

Glomeruloid hemangioma is a rare cutaneous lesion that has been considered as a specific cutaneous marker of POEMS syndrome. Herein, we present the first case of glomeruloid hemangioma associated with TAFRO syndrome, a unique variant of idiopathic multicentric Castleman disease. The patient is a 74-year-old woman presented with fever, cervical lymphadenopathy, thrombocytopenia, bilateral pleural effusions and ascites. Biopsy of the lymph node revealed multicentric Castleman disease-like histology and bone marrow biopsy showed mild reticulin fibrosis, consistent with TAFRO syndrome. The patient simultaneously developed multiple skin lesions, which were histologically confirmed as glomeruloid hemangioma. Multiple immunoglobulin-positive granules were detected in the proliferating endothelial cells. Glomeruloid hemangioma is not specific to POEMS syndrome and can be a manifestation of TAFRO syndrome.

Potential roles of allograft inflammatory factor-1 in the pathogenesis of hemangiomas.

Hemangiomas are benign tumors of the vascular endothelium and are the most common tumors of infancy. These tumors are characterized by an initial phase of rapid proliferation in the first months of life, which is followed, in most cases, by spontaneous slow involution. Despite their high prevalence, their detailed pathogenesis remains unknown. Recent studies suggest that immunity responses, inflammatory cells and their precursors, myeloid cells, play important roles in the growth and involution of hemangiomas. The allograft inflammatory factor-1 is a powerful gene that is involved in several kinds of inflammatory response-related diseases. Studies also show that it is implicated in angiogenesis, proliferation and differentiation of stem cells, and development of tumors. Taken all these evidences into consideration, we hypothesize that allograft inflammatory factor-1 plays potential roles in pathogenesis, proliferation and involution of hemangioma. Investigating the role of allograft inflammatory factor-1 in the proliferation and involution of hemangioma will lead to a better understanding of pathogenesis of this lesion. Furthermore, the subtle regulation of allograft inflammatory factor-1 in the involution of hemangiomas will help design a new anti-angiogenic therapy for some tumors.

Immune response: A possible role in the pathophysiology of hemangioma.

Hemangioma is a distinct category of benign vascular tumors characterized by presentation within the first weeks of life, rapid growth during the first year and variable degree of spontaneous involution over a period of several years. Recent research reported that CD8+ T cells in hemangiomas, and the endothelia of hemangioma uniquely expressed leukocyte marker FCgammaRII and myeloid cell marker. Presence of high levels of indoleamine 2,3-dioxygenase in proliferating hemangiomas and significantly decreasing during involution was also confirmed. Topical application of imiquimod cream, an immune regulator, to proliferating hemangiomas apparently accelerated regression of the lesions. These findings suggest immune response may be involved in the pathogenesis of hemangioma. The endothelia of hemangioma may express various markers to escape the immune surveillance. An immune response may be one of the mechanisms for hemangioma regression. Strategies with systemically or locally applying immune regulator into the tumor may be an applicable way in accelerating the involution of hemangioma.

[Littoral cell angioma of spleen: a clinicopathologic study of 17 cases].

OBJECTIVE: To study the clinicopathologic features and immunophenotype of splenic littoral cell angioma. METHODS: The clinical features, radiologic findings and histopathology of 17 cases of splenic littoral cell angioma were retrospectively reviewed. Immunohistochemical study was carried out on paraffin-embedded tissues, using normal spleen, cases of congestive splenomegaly and cavernous hemangioma as controls. RESULTS: All the 17 cases had similar clinical manifestations and radiologic findings. There was mild to moderate splenomegaly, with solitary or multifocal space-occupying lesions. Hepatic cysts were observed in 5 of the 17 cases. One case was also accompanied by serous cystadenoma of ovary. Gross examination revealed enlarged spleen containing single or multiple tan-colored nodules which ranged from 0.2 cm to 6.0 cm in diameter. Histologically, the lesions consisted of anastomosing vascular channels, sometimes with papillary or cavernous appearance. Two types of component cells were identified. A population of smaller cells lined the vascular channels, while another population of larger cells often floated in the vascular lumen. Both cell populations showed little cytologic atypia. Immunohistochemical study demonstrated that the smaller cells of all cases were positive for CD31 and polyclonal factor VIII-related antigen. They were negative for CD34, histiocytic markers and S-100 protein. CD8 and CD21 were expressed in 1 and 1 of the 17 cases respectively. On the other hand, the larger cells expressed histiocytic markers, including CD68 (KP1 and PG-M1), CD163 and lysozyme. There was also focal positivity for CD31. The staining for CD34, monocolonal factor VIII-related antigen and S-100 protein was negative. The immunophenotype of splenic littoral cell angioma was different from that of the controls. CONCLUSIONS: Littoral cell angioma is a benign condition, likely secondary to hemodynamic disturbance in spleen. The littoral cells become hyperplastic and anastomose, resulting in a hemangioma-like growth associated with histiocytic reaction. Attention to the characteristic histopathologic findings and immunophenotype are crucial for diagnosis.

Human endothelial cells expressing polyoma middle T induce tumors.

The middle T oncogene of murine polyomavirus (PymT) rapidly transforms and immortalizes murine embryonic endothelial cells (EC), leading to the formation of vascular tumors in newborn mice, by recruitment of host, non-transformed EC. These tumors are reminiscent of human vascular tumors like cavernous hemangioma, Kaposi's sarcoma or those characterizing Kasabach-Merrit syndrome. Here we investigate the in vitro and in vivo behavior of human primary umbilical cord vein EC expressing PymT. While PymT has been unable to transform human fibroblasts in earlier experiments or controls done here, mT expressing EC (PymT-EC) derived by infection with pLX-PymT retrovirus induce hemangiomas in nu/nu mice. These tumors contain not only human cells but also recruited mouse EC as shown by the presence of human and murine CD31 positive EC. In vitro analysis shows that PymT-EC retain endothelial specific markers like CD31, Von Willebrand factor, and VE-cadherin, and reach the confluence without signs of overgrowth. They are also responsive to vascular endothelial growth factor-A. However, their proliferation rate is increased. The balance between urokinase-type plasminogen activator and plasminogen activator inhibitor-1 is modified; RNA and catalytic activity for the former are elevated while PAI-1 RNA is reduced. In contrast with murine model, where the PymT EC cells become immortal, the effects induced by PymT in human EC are transient. After 12-15 passages, human PymT EC stop proliferating, assume a senescent phenotype, and lose the ability to induce hemangiomas. At the same time both the amount of middle T protein and the level of activation of pp60c-src lower.