Ultrastructural spectrum of hemangiopericytoma: a comparative study of fetal, adult, and neoplastic pericytes

Neural crest cell-derived pericytes act as pro-angiogenic cells in human neocortex development and gliomas

Central nervous system diseases involving the parenchymal microvessels are frequently associated with a ‘microvasculopathy’, which includes different levels of neurovascular unit (NVU) dysfunction, including blood–brain barrier alterations. To contribute to the understanding of NVU responses to pathological noxae, we have focused on one of its cellular components, the microvascular pericytes, highlighting unique features of brain pericytes with the aid of the analyses carried out during vascularization of human developing neocortex and in human gliomas. Thanks to their position, centred within the endothelial/glial partition of the vessel basal lamina and therefore inserted between endothelial cells and the perivascular and vessel-associated components (astrocytes, oligodendrocyte precursor cells (OPCs)/NG2-glia, microglia, macrophages, nerve terminals), pericytes fulfil a central role within the microvessel NVU. Indeed, at this critical site, pericytes have a number of direct and extracellular matrix molecule- and soluble factor-mediated functions, displaying marked phenotypical and functional heterogeneity and carrying out multitasking services. This pericytes heterogeneity is primarily linked to their position in specific tissue and organ microenvironments and, most importantly, to their ontogeny. During ontogenesis, pericyte subtypes belong to two main embryonic germ layers, mesoderm and (neuro)ectoderm, and are therefore expected to be found in organs ontogenetically different, nonetheless, pericytes of different origin may converge and colonize neighbouring areas of the same organ/apparatus. Here, we provide a brief overview of the unusual roles played by forebrain pericytes in the processes of angiogenesis and barriergenesis by virtue of their origin from midbrain neural crest stem cells. A better knowledge of the ontogenetic subpopulations may support the understanding of specific interactions and mechanisms involved in pericyte function/dysfunction, including normal and pathological angiogenesis, thereby offering an alternative perspective on cell subtype-specific therapeutic approaches.

Neural crest cell-derived pericytes act as pro-angiogenic cells in human neocortex development and gliomas

Central nervous system diseases involving the parenchymal microvessels are frequently associated with a ‘microvasculopathy’, which includes different levels of neurovascular unit (NVU) dysfunction, including blood–brain barrier alterations. To contribute to the understanding of NVU responses to pathological noxae, we have focused on one of its cellular components, the microvascular pericytes, highlighting unique features of brain pericytes with the aid of the analyses carried out during vascularization of human developing neocortex and in human gliomas. Thanks to their position, centred within the endothelial/glial partition of the vessel basal lamina and therefore inserted between endothelial cells and the perivascular and vessel-associated components (astrocytes, oligodendrocyte precursor cells (OPCs)/NG2-glia, microglia, macrophages, nerve terminals), pericytes fulfil a central role within the microvessel NVU. Indeed, at this critical site, pericytes have a number of direct and extracellular matrix molecule- and soluble factor-mediated functions, displaying marked phenotypical and functional heterogeneity and carrying out multitasking services. This pericytes heterogeneity is primarily linked to their position in specific tissue and organ microenvironments and, most importantly, to their ontogeny. During ontogenesis, pericyte subtypes belong to two main embryonic germ layers, mesoderm and (neuro)ectoderm, and are therefore expected to be found in organs ontogenetically different, nonetheless, pericytes of different origin may converge and colonize neighbouring areas of the same organ/apparatus. Here, we provide a brief overview of the unusual roles played by forebrain pericytes in the processes of angiogenesis and barriergenesis by virtue of their origin from midbrain neural crest stem cells. A better knowledge of the ontogenetic subpopulations may support the understanding of specific interactions and mechanisms involved in pericyte function/dysfunction, including normal and pathological angiogenesis, thereby offering an alternative perspective on cell subtype-specific therapeutic approaches.

Intracranial Meningeal Hemangiopericytomas: An Analysis of Factors Affecting Outcome in 39 Cases Managed with Multimodality Treatment

Aim

To retrospectively evaluate the outcome of patients with intracranial meningeal hemangiopericytomas (MHPCs) and to analyze various factors for recurrence and survival in these patients.

Materials and Methods

We retrospectively reviewed the clinical data of 39 patients undergoing microsurgical resection for MHPCs at our institute from 2009 to 2015.

Results

Gross total excision (GTE) was achieved in 27 (69.2%) patients, whereas 12 (30.8%) underwent subtotal excision (STE). A total of 25 patients received radiotherapy (RT) (Conventional RT-15; GKT-10), 21 patients had a low grade tumor, while 18 had an anaplastic variant. Twenty patients (51.3%) developed recurrences and the average recurrence-free survival (RFS) was 56 months (range: 12-180 months). Eight patients (20.5%) died during the study period. The average overall survival (OS) was 77.2 months (range: 36-192 months). Two patients (5.1%) developed systemic metastases during follow-up. Patient age was not found to affect RFS or OS. GTE was associated with prolonged RFS and OS but the impact was not statistically significant (P-values = 0.160 and 0.414, respectively). Low tumor grade was associated with statistically significant longer RFS as well as OS (P-values = 0.049 and 0.013, respectively). Addition of adjuvant RT was associated with statistically significant prolongation of RFS (P value = 0.016); however, it was not associated with statistically significant OS benefits (P-value = 0.758).

Conclusions

Our study suggests that a greater extent of excision, lower tumor grade, and addition of adjuvant RT have a positive impact on both RFS and OS; however, low grade and adjuvant RT were the only factors associated with statistically significant prolongation of RFS and only tumor grade was associated with statistically significant OS benefits.

Pericytes in Brain Injury and Repair After Ischemic Stroke

Pericytes are functional components of the neurovascular unit (NVU). They provide support to other NVU components and maintain normal physiological functions of the blood-brain barrier (BBB). The brain ischemia and reperfusion result in pathological alterations in pericytes. The intimate anatomical and functional interactions between pericytes and other NVU components play pivotal roles in the progression of stroke pathology. In this review, we depict the biology and functions of pericytes in the normal brain and discuss their effects in brain injury and repair after ischemia/reperfusion. Since ischemic stroke occurs mostly in elderly people, we also review age-related changes in pericytes and how these changes predispose aged brains to ischemic/reperfusion injury. Strategies targeting pericyte responses after ischemia and reperfusion may provide new therapies for ischemic stroke.

Gamma knife radiosurgery for residual or recurrent intracranial hemangiopericytomas

Residual or recurrent hemangiopericytoma (HPC) has been treated with radiosurgery; however, its long-term outcome is not well known. This study is to investigate the long-term outcome of gamma knife radiosurgery (GKS) for residual or recurrent HPCs. We conducted a retrospective analysis of 18 patients who underwent gamma knife radiosurgery for residual or recurrent HPCs. Of the 18 patients, 10 patients had high-grade HPCs (27 tumors) and 8 had low-grade HPCs (13 tumors). Median overall survival (OS) after the first GKS was 134.7months and actuarial survival rate at 1, 5, and 10years was 85.6%, 85.6%, and 37.4%, respectively. At the last follow-up, local tumor control was achieved in 32 (80.0%) of the 40 GKS-treated tumors. New lesions developed out of initial GKS target in 8 patients (44.4%). They were also treated with additional GKS. The actuarial local control rate of 40 tumors at 1-, 3-, and 5-years was 89.3%, 60.9%, and 37.5%, respectively. The median local recurrence-free interval of 40 tumors after initial GKS for each lesion was 86.1months for low-grade and 40.5months for high-grade tumors (p=0.010). Extracranial metastases developed in 7 (38.9%) patients with high-grade pathology and became a cause of death in 3 patients. Intracranial tumor control can be achieved over the long term, though additional GKS is frequently necessary. Extracranial metastasis is common in HPC of high-grade pathology. Close surveillance and aggressive treatment is recommended not only for intracranial tumor but also for possible extracranial metastases.

Hemangiopericytoma of the Thyroid

A 52-year-old woman presented with a painless right thyroid mass of 4 months dura tion, with a recent increase in size in the last few weeks. The neoplasm was character ized by bland spindle cells with a low mitotic rate arranged around vascular elements of variable shape and caliber. Multiple immunohistochemical stains failed to show evi dence of epithelial, neuroendocrine, or specific mesenchymal differentiation. Electron microscopic studies revealed spindle cells with micropinocytotic vesicles, surrounded by variable but sometimes abundant basement lamina-like material. To the authors' knowledge, this is the first report of a typical hemangiopericytoma of the thyroid gland. This lesion must be distinguished from epithelial and neuroendocrine tumors with spindle cells and from other mesenchymal neoplasms that may occur in the thyroid. Int J Surg Pathol 2(4):311-318, 1995

Hemangiopericytoma/solitary fibrous tumor of the greater omentum: A case report and review of the literature

INTRODUCTION

Hemangiopericytoma (HPC) has been first described in 1942 by Stout as a tumor originating from the capillary surrounding pericytes. It is known to occur in any anatomical site, especially the extremities and retroperitoneum.

PRESENTATION OF CASE

We describe a case of a 24year old patient presenting with lower abdominal pain due to a tumor of the greater omentum, the patient was treated by conventional laparotomy with tumor resection and the histological evaluation confirmed the diagnosis Hemangiopericytoma/Solitary fibrous tumor (HPC/SFT). The patient has regularly followed-up with periodic imaging for the last 4 years, with no recurrences.

DISCUSSION AND CONCLUSION

According to our knowledge, HPC rarely develops in the greater omentum, only 20 cases were described in the literature. Primary surgical resection is the treatment of choice. There is no benefit of radiation or systemic chemotherapy. Angiogenic inhibitors represent promising systemic therapeutic concepts.

Meningeal hemangiopericytoma only diagnosed at the time of late bone metastasis

Hemangiopericytoma is a rare neoplasm. Primary meningeal hemangiopericytomas account for 1 to 7% of all meningeal tumors. In the literature, meningeal hemangiopericytomas are mainly case reports, which confirm an aggressive behavior with a high rate of local recurrence and extracranial metastasis. Metastasis can be seen many years after initial surgical excision of the primary tumor, and the most common sites include the bone, liver and lung. We present a pathological study of four meningeal hemangiopericytomas with bone metastases. All patients are male with a mean age of 46.5 years. Metastases only involved bone. Three out of four lesions were initially misdiagnosed as meningiomas. Only one case was initially correctly diagnosed as meningeal hemangiopericytoma. All patients underwent surgery with complete resection. Only the patient immediately diagnosed with meningeal hemangiopericytoma received postoperative radiation therapy. Three patients had bone metastases without local recurrence including the one who received radiation therapy. One patient recurred locally after 7 years, and bone metastasis was found at the same time. Our cases confirm that meningeal hemangiopericytomas are a separate entity and have a high recurrence rate despite complete surgical resection, with extracranial metastases, mainly to bone, even after long intervals.

Hemangiopericytoma: Radical resection remains the cornerstone of therapy

Hemangiopericytomas (HPC) are mesenchymal tumors with a propensity towards chronicity and metastasis. This study aimed to reflect a single institution experience with both World Health Organization (WHO) grade II and III HPC. Pathology records from the years 1990-2013 at the University of Washington were searched to identify tumors unequivocally classified as HPC. Electronic chart review was then utilized to collect pertinent patient data. Of the WHO grade II HPC, there were four men and two women (average age 52 years) while the grade III HPC group had eight men and two women (average age 51 years). Sixty-six percent of WHO grade II tumors were located in the middle or posterior fossa as compared to none of the grade III tumors. Survival analysis revealed a significant survival benefit for patients who underwent complete resection (223 months) versus those with subtotal resection (138 months, p<0.05). Factors such as age, sex, the use of up-front radiation, and whether the patient had a recurrence did not show statistical significance related to overall survival or progression free survival. Radiation in the form of external beam radiotherapy given at the time of the first recurrence did trend towards improved progression free survival (56 months) compared to those patients who were not radiated (22 months, p=0.09) All patients with radical resection went on to never have a recurrence. Our results indicate that HPC are tumors with limited response to radiation and best treated with aggressive resection. Future studies will determine whether molecular-based therapies may provide added adjuvant benefit.

Cellular solitary fibrous tumor (hemangiopericytoma) with anaplasia at cerebellopontine angle--a case report

Cellular solitary fibrous tumor is currently considered a synonym for hemangiopericytoma, as it became increasingly clear that the morphological and immunohistochemical features that separate these two entities have become tenuous, and evidence for a unifying concept has emerged. Furthermore, as no evidence of pericytic differentiation is given in most cases of hemangiopericytoma, this diagnostic term is waning in popularity. We present here a case of cellular solitary fibrous tumor in a 22-year-old man. Neuroimaging revealed a right cerebellopontine angle tumor. Most of the tumor was cellular although some less cellular areas were seen. Sinusoidally dilated large vessels, including staghorn type, were seen. Nuclear pleomorphism and increased mitotic activity (5 mitosis/10 high power field) were regarded as evidence of anaplasia. Diffuse CD34 immunoreactivity and focal positivity for Factor XIIIa were seen in the tumor, which was negative for EMA and S100. The tumor also displayed rich reticulin network. Solitary fibrous tumor at cerebellopontine angle is rare, and 20 such cases (five reported as hemangiopericytoma) have been reported in the English literature.

Renal Myopericytoma: Case Report and Review of Literature

Myopericytoma arising in the visceral organs is rare and only 1 case of renal myopericytoma has been reported in the literature to date. We report the second case of myopericytoma arising in the kidney in a 40-year-old Hispanic woman who presented with pain on the left side of the abdomen and frequent urination. Abdominal computed tomography scan showed an exophytic left-sided renal mass. Partial nephrectomy was performed. The patient remains free of disease at 24 months after diagnosis. Our case is histologically distinct from the previously described case as it lacks the “hemangiopericytic/glomangiopericytoma” pattern. The tumor in our case showed the characteristic pattern of myopericytoma and an additional glomus tumorlike pattern. The tumor cells showed diffuse reactivity for vimentin, smooth muscle actin, smooth muscle myosin heavy chain, and muscle-specific actin in both morphologic patterns and strong diffuse CD34 expression in glomus tumorlike focus. This case report adds to the morphologic heterogeneity of myopericytomas.

Select Neoplasms of the Sinonasal Tract

The sinonasal tract (SNT) includes the nasal cavity and paranasal sinuses (maxillary, ethmoid, frontal, and sphenoid) and may give rise to a variety of nonneoplastic and neoplastic proliferations, including benign and malignant neoplasms. The benign neoplasms of the SNT include epithelial neoplasms of surface epithelial origin, minor salivary gland origin, and mesenchymal origin. The spectrum of malignant neoplasms of the SNT includes epithelial malignancies, sinonasal undifferentiated carcinoma, malignant salivary gland neoplasms, neuroectodermal neoplasms, neuroendocrine neoplasms, melanocytic neoplasm, and sarcomas. This article concentrates on some of the more common types of benign and malignant neoplasms.

The status of MGMT protein expression is a prognostic factor for meningeal hemangiopericytoma: a clinicopathologic and immunohistochemical study of 12 cases at a single institution

Meningeal hemangiopericytoma (HPC) is a clinicopathologically well-characterized malignancy with a high tendency to recur locally and to metastasize outside the central nervous system (CNS). We render clinicopathologic features of 12 cases of this uncommon tumor to further elucidate the relationship between the status of the DNA-repair enzyme O(6)-methylguanine-DNA methyltransferase (MGMT) and the prognosis. Twenty-five specimens of meningeal HPC belonging to 12 patients were obtained at a single institution from 1992 to 2001. Correlations of histologic parameters, immunohistochemical study and clinical features were assessed. This series included five men and seven women with a median age of 37.5 years at the first surgery. The median post-operative follow-up period was 7.6 years. Six patients (55%) had single or multiple local tumor recurrences. The mean time to recurrence was 6.7 years. Distant metastasis occurred in three patients (27%) at a mean time of 6.5 years after first operation. The most frequent metastatic sites were liver and lung. Histopathologically, eight primary tumors (67%) belonged to WHO grade II, while four primary tumors (33%) belonged to WHO grade III. Immunohistochemically, 18% primary tumors exhibited 3+ to 4+ nuclear staining for MGMT protein, 18% exhibited 2+ staining, and 64% exhibited 0 to 1+ staining. The overall survival rate was 67 and 33% for primary tumors with 0 to 1+ and 2+ to 4+ MGMT staining, respectively (P = 0.018). The study illustrates aggressive behavior of meningeal HPC and the prognostic value of the status of MGMT protein expression.

Hemangiopericytoma: long-term outcome revisited. Clinical article

OBJECT

Hemangiopericytomas are rare tumors that behave aggressively with a high rate of local recurrence and distant metastases. With the aim of determining the outcome and response to various treatment modalities, a series of 39 patients who underwent microsurgical resection for primary meningeal hemangiopericytoma over a 24-year period is presented.

METHODS

Patients with hemangiopericytoma were identified from histopathology records and their medical records were analyzed retrospectively by 2 independent reviewers to collect data on surgical treatment, adjuvant therapy, postoperative course, local or distant recurrence, and follow-up.

RESULTS

Of the 39 patients, 19 were male and 20 were female. Mean patient age was 44.1 years. Thirty-four tumors were intracranial and 5 were spinal. The mean follow-up period was 123 months. Twenty-eight patients developed local recurrence. The recurrence rate at 1, 5, and 15 years was 3.5%, 46%, and 92%, respectively. Extraneural metastasis occurred in 8 patients (26%) at an average of 123 months after initial surgery. Recurrences and metastases were treated by surgical excision, external beam radiation therapy (EBRT), chemotherapy, and/or stereotactic radiosurgery. Adjuvant EBRT following initial surgery was found to extend the disease-free interval from 154 months to 254 months, although it did not prevent the development of metastasis. In those patients with EBRT and complete resection, the mean recurrence-free interval was found to be 126.3 months longer (p = 0.04) and overall survival 126 months longer than without EBRT. Furthermore, adjusting for resection, patients undergoing EBRT had 0.33 times increased risk of recurrence compared with those who did not (p = 0.03). A majority of patients remained able to live independently despite revision surgery for recurrence.

CONCLUSIONS

The mean follow-up of this patient series represents the longest follow-up duration published to date and demonstrates extended survival in a significant number of patients with hemangiopericytoma. Gross-total resection followed by adjuvant EBRT provides patients with the highest probability of an increased recurrence-free interval and overall survival. Prolonged survival justifies long-term follow-up and aggressive treatment of initial, recurrent, and metastatic disease.

Hemangiopericytomas of the spine: case report and review of the literature

We describe a rare case of a primary intracranial meningeal hemangiopericytoma (HPC) with late metastasis to the cervical spine. A 36-year-old woman had a left occipital lesion that was histopathologically identified as HPC. Fourteen years after resection, the tumor recurred and was treated with radiotherapy. Three years later, CT imaging showed a large mass in the liver consistent with metastatic HPC, and MRI of the cervical spine showed an extensive lesion of the C3 vertebral body. The patient underwent C3 corpectomy with en-bloc tumor removal and follow-up radiation with no local recurrence or other spinal metastasis for the following 4 years. Regardless of the subtype of spinal HPC, complete surgical removal and radiotherapy appear to be treatment of choice.

Malignant primary pulmonary tumor with hemangiopericytoma-like features: conventional hemangiopericytoma versus solitary fibrous tumor

Although extremely rare, the primitive lung hemangiopericytoma in adults is similar to hemangiopericytomas with other soft tissue localizations. Although generally benign and curable after radical surgery, it might also have a malignant clinical course with dissemination in both lungs, infiltration of vital organs (heart, pulmonary artery), extension to the adjacent tissues, and even pulmonary metastases. The treatment of choice is the complete tumor resection with negative surgical margins after excision. Certain histologic features might indicate a malignant potential. The clinical outcome of patients is variable: some are cured after radical surgery and others might present relapse and recurrences that necessitate a second intervention, radiation therapy, and/or chemotherapy. Over the years, the conventionally-defined hemangiopericytoma concept has evolved because of the nonspecific histologic growth pattern (characteristic monotonous appearance, moderate or high cellularity, and a well-developed branching vascular pattern) shared by numerous, unrelated benign or malignant lesions. Hemangiopericytoma is no longer considered a specific entity but rather as a characteristic growth pattern; in the heterogeneous group of hemangiopericytoma-like neoplasms, many lesion categories have been individualized and defined. We report an uncommon case of primitive lung tumor exhibiting hemangiopericytoma-like features, with an aggressive, fatal clinical course. Because of the major histologic overlap between solitary fibrous tumor and hemangiopericytoma and lack of clear classification criteria, we encountered difficulty in including this case in a known clinical entity; primitive solitary fibrous tumor of the lung, which mimics lung hemangiopericytoma, seemed to be the most plausible diagnosis. We discuss the case particularities and the radiologic and pathologic correlations.

Radiation-induced rhabdomyosarcomatous transformation of a recurrent meningeal haemangiopericytoma

A 53-year-old woman presented in 1979 with a posterior fossa meningeal haemangiopericytoma (HPC) for which she underwent surgical resection and post-operative radiotherapy. Repeated tumour recurrences occurred 18 years afterwards which were treated with resections and stereotactic radiotherapy. Surgery for tumour recurrence in 2005 revealed features of rhabdomyosarcomatous transformation. To our knowledge, this is the first reported case of rhabdomyosarcomatous transformation within a HPC which was likely to be radiation-induced, and was associated with relentless disease progression more than 20 years after the initial presentation.

Pulmonary lipomatous hemangiopericytoma: report of a rare tumor and comparison with solitary fibrous tumor

Lipomatous hemangiopericytoma is a rare mesenchymal tumor showing areas of lipid-containing cells admixed with a spindle-cell component. Like other hemangiopericytomas, it shows a similar vascular pattern to solitary fibrous tumor and, partly for this reason, it and other hemangiopericytomas have been subsumed into solitary fibrous tumor. The present study provides a comprehensive documentation of a single case of pulmonary lipomatous hemangiopericytoma of the lung, the first to be described at this site, and compares it with solitary fibrous tumor, in terms of clinical, histological, immunohistochemical, ultrastructural, and cytogenetic findings. Apart from the lipid-laden-cell component, pulmonary lipomatous hemangiopericytoma and solitary fibrous tumor were similar histologically. Bcl-2 was positive in both. CD34 was minimally expressed in pulmonary lipomatous hemangiopericytoma, which possessed some non-descriptive intercellular junctions, a feature shared by solitary fibrous tumor, which was CD34 positive. However, one of the latter was rich in gap junctions, a feature consistent with strong connexin (Cx) 43 staining and the existence, hitherto unappreciated, of a CD34/Cx43-positive tumor cell network. In pulmonary lipomatous hemangiopericytoma, chromosomal deletions of 43-44, X, -Y were found. In solitary fibrous tumor, 46, XY, del(13)(q?) abnormalities and abnormalities involving chromosome 10 were frequently observed. These similarities and differences are discussed in the context of the currently favored diagnostic fusion of hemangiopericytoma and solitary fibrous tumor.

Solitary fibrous tumours of the infratemporal fossa. Two case reports

INTRODUCTION

The solitary fibrous tumour is a rare neoplasm originally described as a pleural tumour. An increasing number of different locations are described in the literature. Among the extrapulmonary sites, head and neck can be involved and particularly the nose, the paranasal sinuses, the submandibular region, the parapharyngeal space and the infratemporal fossa.

MATERIAL

Two cases, one of a young woman and another of an elderly gentleman are reported, each presenting with a solitary fibrous tumour of the infratemporal fossa. In one case an antero-lateral, transcranio-facial and in the other, a transmandibular approach (without labiotomy) were utilized. In both cases complete excision of the lesion and good cosmetic results were achieved.

RESULTS

Both patients were free from the disease for 5 postoperatively.

CONCLUSIONS

To date, very few cases of solitary fibrous tumour of the craniofacial complex have been observed to enable an accurate prognosis. Thus, treatment and follow-up should be identical to fibrous tumours located in other areas.

Solitary fibrous tumour and haemangiopericytoma: evolution of a concept

Haemangiopericytoma (HPC) was described in 1942 by Stout and Murray as a distinctive soft tissue neoplasm, presumably of pericytic origin, exhibiting a characteristic well-developed "staghorn" branching vascular pattern. Over the years, it appeared that this growth pattern was a non-specific one, shared by numerous, unrelated benign and malignant lesions, and that HPC was better considered as a diagnosis of exclusion. Three categories of lesion may now be individualized within the heterogeneous group of HPC-like neoplasms. The first category corresponds to those non-HPC neoplasms that occasionally display HPC-like features (e.g. synovial sarcoma). Lesions belonging to the second category show clear evidence of myoid/pericytic differentiation and correspond to true HPCs. They generally show a benign clinical course, and include glomangiopericytoma/myopericytoma, infantile myofibromatosis (previously called infantile HPC), and a subset of sinonasal HPCs. The third category is the solitary fibrous tumour (SFT) lesional group, which includes fibrous-to-cellular SFTs, and related lesions such as giant cell angiofibromas and lipomatous HPCs. In practice, any HPC-like lesion can be allocated to one of these categories, leaving the ill-defined "haemangiopericytoma" category empty.

Sinonasal hemangiopericytoma-like tumor with true pericytic myoid differentiation: a clinicopathologic and immunohistochemical study of five cases

BACKGROUND

Sinonasal hemangiopericytoma-like tumor (SHPCL) is an uncommon vascular tumor that is sometimes difficult to diagnose.

METHOD

We report five cases arising from the nasal cavity. The tumors were subdivided into two types, prototype and soft tissue type, by the difference in histologic features.

RESULTS

The prototype, made up of three tumors, is characterized by uniform, spindle-shaped myoid cells that have eosinophilic cytoplasm and uniform nuclei and lay down in an orderly fashion. The soft tissue type, made up of two tumors, is similar to the hemangiopericytoma of soft tissue. Immunohistochemically, the tumors were positive for vimentin (100%), smooth muscle actin (80%), muscle-specific actin (100%), fibroblast growth factor-2 (100%), and vascular endothelial growth factor (100%). All were negative for cytokeratin, desmin, CD34, and factor VIII-related antigen. These histopathologic features suggest myoid differentiation and angiogenic activity of the tumors. All the tumors were treated with wide surgical excision. Only one case of soft tissue-type tumor with active mitoses received additional postoperative radiotherapy. No recurrence was found during 13 to 120 months of follow-up.

CONCLUSIONS

Our data suggest that SHPCL with convincing myoid differentiation may have a more favorable clinical course than its soft tissue counterpart.

Ultrastructural spectrum of solitary fibrous tumor: a unique perivascular tumor with alternative lines of differentiation

Eight tumors diagnosed as solitary fibrous tumor (SFT) of the oral cavity were studied. Histologic spectrum was entirely comparable with the extrapleural SFT of other sites. One tumor had glomus tumor-like foci. Immunohistochemical results confirmed most of the previous observations, indicating characteristic expression of vimentin, CD34, bcl-2, and CD99. Factor XIIIa and alpha-smooth muscle actin were less commonly reactive and a very few cells were faintly positive for factor VIII-related antigen and Ulex europaeus agglutinin 1. All were essentially negative for S-100 protein, desmin, CD31, and CD68. In stark contrast to the conclusive immunoprofile, ultrastructural investigation of six tumors demonstrated considerable cellular heterogeneity. Other than fibroblasts, perivascular undifferentiated cells and pericytes predominated, but endothelial cells were regularly present. There was a distinctive proliferation of pericytic cells in four tumors, one of which had glomoid foci of myopericytes. The extreme increase in number of Weibel-Palade bodies occurred in voluminous capillary endothelium. Occasional single and clustered cells with consistent features of endothelium showed intracytoplasmic lumen formation. Such composite cells constituted an integral segment of richly vascularized SFT. Myofibroblastic form smooth muscle differentiation was present in only a minority of cells. From phenotypic analysis by electron microscopy, SFT may originate from a unique, perivascular multipotent mesenchyme sharing with its lineage with pericytes, fibroblasts, and infrequently, endothelium. Consequently, morphological features of SFT may become diversely varied by whether predominantly constituent cells are undifferentiated, pericytic or fibroblastic in nature.

Low-grade sarcomas with CD34-positive fibroblasts and low-grade myofibroblastic sarcomas

A subset of low-grade fibrosarcomas is composed of CD34-positive spindle cells. These include dermatofibrosarcoma, its morphologic variants, and its associated fibrosarcoma, solitary fibrous tumor, hemangiopericytoma and their malignant counterparts, and some cases of myxoinflammatory fibroblastic sarcoma. Dermatofibrosarcoma and related lesions are characterized by a t(17;22)(q22;q13) rearrangement resulting in fusion of the genes COL1A (17q21-22) and PDGFB1 (22q13). Solitary fibrous tumor displays varying cellularity and fibrosis and a peripheral hemangiopericytomatous pattern; most tumors formerly called hemangiopericytoma are now subsumed into the category of solitary fibrous tumor, although a few strictly defined examples are recognized; however, these are probably not composed of pericytes. Myofibroblastic malignancies are best identified by electron microscopy, with which varying degrees of differentiation, including the presence of fibronexus junctions, can be identified. Low-grade sarcomas showing myofibroblastic differentiation include myofibrosarcomas and inflammatory myofibroblastic tumors. Myofibrosarcomas are spindle cell neoplasms that occur in children or adults in the head and neck, trunk, and extremities as infiltrative neoplasms and that display a fascicular or fasciitis-like pattern with focal nuclear atypia and variable expression of myoid antigens. These sarcomas are prone to recurrence and a small number metastasize. Inflammatory myofibroblastic tumor (synonymous with inflammatory fibrosarcoma) is a neoplasm arising predominantly in childhood, and frequently in intraabdominal locations. It has spindle cells in fascicular, fasciitis-like and sclerosing patterns, with heavy chronic inflammation including abundant plasma cells. Many IMT have clonal chromosomal abnormalities involving 2p22-24, and fusion of the ALK gene with tropomyosin 3 (TPM3-ALK) or tropomyosin 4 (TPM4-ALK) is found in a subset.

Precision radiotherapy for hemangiopericytomas of the central nervous system

BACKGROUND

Radiotherapy (RT) plays a major role in the management of hemangiopericytomas (HAP). The present analysis evaluates the role of precision RT in the management of HAP of the central nervous system (CNS) and represents one of the largest series of HAP treated with RT that can be found in the literature.

METHODS

Of 37 consecutive patients with histologically confirmed HAP who were treated at the institution between 1984 and 2004, the majority, 25 tumors, was localized within the skull base (n = 25) and 4 tumors were localized at the spine. In 25 patients, high-precision RT was delivered as fractionated stereotactic RT or intensity modulated RT. Median age at primary diagnosis was 40.5 years (range, 10-77 yrs). After primary diagnosis, surgical resection was performed in 23 patients. A median total dose of 54 Gy was delivered in a fractionation of 5 x 1.8-2 Gy per week. The median planning target volume was 58.2 mL (range, 10-412 mL). The median follow-up time was 34 months (range, 3-166 mos).

RESULTS

Radiotherapy was well tolerated by all patients. Seventeen patients of this series remain alive. Overall survival rates at 5 and 10 years are 100% and 64%, respectively. Actuarial survival rates after RT were 85% and 69% at 3 and 5 years, respectively. Progression-free survival after RT 80% and 61% at 3 and 5 years, respectively.

CONCLUSION

High-precision RT is an effective and safe treatment modality for patients with HAP of the CNS and the spine and achieves highly acceptable tumor control, while sparing normal tissue.

Transscleral resection of a ciliary body leiomyoma in a child: case report and review of the literature

PURPOSE

To present the case of a patient with leiomyoma of the ciliary body and discuss the histological features and treatment of this rare intraocular tumor. METHODS/CASE REPORT: A 13-year-old boy presented with an asymptomatic tumor of the right eye. Visual acuity was 20/20 in both eyes. Ophthalmoscopy revealed an amelanotic, vascularized ciliary body tumor with exudative retinal detachment and partial transillumination. On ultrasound examination the tumor height was 8 mm and a low internal reflectivity was found. T2-weighted MRI scans showed a hypointense and T1-weighted scans a hyperintense intraocular mass with significant Gd-TPA enhancement. On the assumption that the diagnosis was consistent with an amelanotic ciliary body melanoma, a transscleral resection with adjuvant ruthenium-106 brachytherapy was performed. Visual acuity was 20/40 at 6 months after the operation.

RESULTS

Routine stains revealed a pleomorphic tumor composed mainly of spindle cells with palisading in some areas and a prominent intercellular fibrillary background. Immunohistochemistry showed positivity for desmin, vimentin and actin. No reactivity with S-100 and HMB-45 was seen. Intracytoplasmatic filaments and micropinocytotic vesicles were detected by transmission electron microscopy. These findings were consistent with the diagnosis of a ciliary body leiomyoma.

CONCLUSION

Typical clinical features of leiomyoma include a dome-shaped configuration and translucency, but the final diagnosis can only be confirmed by histology with the aid of immunohistochemistry and electron microscopy. Though rare, leiomyoma should be considered in the differential diagnosis of amelanotic uveal tumors. Transscleral resection is the treatment of choice of anterior uveal leiomyomas, with a fairly good visual prognosis.

Delayed manifestation of spinal metastasis: a special feature of hemangiopericytoma

Metastatic hemangiopericytoma to the spine is rare, and operative management of these highly vascularized tumors is challenging. Review of the literature identified only seven previously reported cases. Metastases of hemangiopericytomas to the spine are diagnosed often only after a long delay following resection of the primary tumors. To emphasize the clinical and histopathological features of metastatic hemangiopericytoma to the spine and to review treatment options, a case of a delayed metastatic hemangiopericytoma to the cervicothoracic spine is reported: a 48-year-old woman presented with a large metastatic hemangiopericytoma to the cervicothoracic spine causing left-sided cervicobrachialgias and gait disturbance. Magnetic resonance imaging studies revealed a large left-sided dumbbell-shaped intraspinal and extraspinal tumor from C6 to T2. The patient underwent two-staged total removal of the cervicothoracic mass with posterior stabilization and subsequent radiotherapy. Histopathological findings revealed a malignant hemangiopericytoma which had identical features to the primary cranial meningeal tumor removed 8 years earlier. The radicular symptoms and the gait ataxia disappeared, postoperatively. One year later, however, new metastases were present. Patients with hemangiopericytoma should be controlled regularly for local recurrence and systemic tumor spread. The best available treatment for delayed metastasis to the spinal column is complete tumor removal followed by postoperative radiotherapy.

Sinonasal-type hemangiopericytoma: a clinicopathologic and immunophenotypic analysis of 104 cases showing perivascular myoid differentiation

Sinonasal-type hemangiopericytoma is an uncommon upper aerodigestive tract tumor of uncertain cellular differentiation. We report 104 cases of sinonasal-type hemangiopericytoma diagnosed between 1970 and 1995 from the files of the Armed Forces Institute of Pathology. There were 57 females and 47 males ranging in age from 5 to 86 years (mean 62.6 years). The most common clinical presentation was airway obstruction (n = 57) and/or epistaxis (n = 54), with symptoms averaging 10 months in duration. The tumors involved the nasal cavity alone (n = 47) or also a paranasal sinus (n = 26), were polypoid, and measured an average of 3.1 cm. Histologically, the tumors were submucosal and unencapsulated and showed a diffuse growth with fascicular (n = 37) to solid (n = 50) to focally whorled (n = 7) patterns. The tumor cells were uniform in appearance with minimal pleomorphism and had spindle-shaped (n = 82) to round/oval (n = 18) nuclei with vesicular to hyperchromatic chromatin and eosinophilic to amphophilic to clear-appearing cytoplasm with indistinct cell borders. Multinucleated (tumor) giant cells were identified in a minority of cases (n = 5). Mitotic figures were inconspicuous and necrosis was absent. The tumors were richly vascularized, including staghorn-appearing vessels that characteristically had prominent perivascular hyalinization (n = 92). An associated inflammatory cell infiltrate that included mast cells and eosinophils was noted in the majority of cases (n = 87). The immunohistochemical profile included reactivity with vimentin (98%), smooth muscle actin (92%), muscle specific actin (77%), factor XIIIa (78%), and laminin (52%). Surgery was the treatment of choice for all of the patients; adjunctive radiotherapy was given to four patients. Recurrences developed in 18 patients within 1-12 years from diagnosis. Ninety-seven patients were either alive (n = 51, mean 16.5 years) or dead (n = 46, mean 9.6 years) but free of disease. Four patients had disease at the last follow-up: three died with disease (mean 3.6 years) and one patient is alive with disease (28.3 years). Recurrent tumor (17.8%) can be managed by additional surgery. The majority of sinonasal-type hemangiopericytomas behave in a benign manner with excellent long-term prognosis (88% raw 5-year survival) following surgery alone. Sinonasal-type hemangiopericytomas have a characteristic light microscopic appearance with an immunophenotypic profile resembling that of glomus tumors.

Hemangiopericytoma in the central nervous system: treatment, pathological features, and long-term follow up in 38 patients

OBJECT

The authors reviewed the Mayo Clinic experience with the treatment of hemangiopericytoma in the primary central nervous system (CNS).

METHODS

A retrospective study of all patients at the Mayo Clinic revealed 38 who had been treated for hemangiopericytoma in the CNS. Twenty of these patients were diagnosed in the decade between 1990 and 2000; 18 were initially diagnosed and underwent surgery before 1990. In the patients treated since 1990, the 5-year Kaplan-Meier survival rate was 93%. The 5-year disease-free survival rate was 89%. Sixty percent of patients treated with the aid of stereotactic radiosurgery for recurrent disease were alive 4.4 years after their initial treatment. Salvage chemotherapy was not effective. No survival benefit was detected inpatients who had received initial adjuvant external-beam radiation therapy. High-grade tumors recurred 6.7 years earlier than did low-grade lesions (p = 0.004).

CONCLUSIONS

The 5-year survival rate in patients with hemangiopericytoma of the CNS has improved at the authors' institution during the last 10 years. Although the reason for this is not entirely clear, the authors suspect that the improved treatment of patients with cancer, a 0% intraoperative mortality rate, and the use of radiosurgery in the treatment of recurrent disease all likely contribute. High-grade tumors recurred statistically significantly earlier than low-grade lesions. Current chemotherapies are ineffective in the treatment of hemangiopericytoma of the CNS.

Conventional hemangiopericytoma: modern analysis of outcome

BACKGROUND

Hemangiopericytoma (HPC) is a rare vascular tumor, and pathologic distinction from synovial sarcoma and solitary fibrous tumor is a significant problem due to shared histologic features. In the current report the authors defined the clinical behavior and prognosis for patients with HPC.

METHODS

Between July 1982 and February 1998, 62 patients with a diagnosis of primary, recurrent, or metastatic HPC were identified from a prospectively maintained database. The pathology of all cases for which material was available (57 cases) was re-reviewed for histologic confirmation of the HPC diagnosis. Using strict pathologic criteria, including immunohistochemistry and electron microscopy, tumors from 25 of 57 patients qualified for the diagnosis of conventional hemangiopericytoma; those tumors formed the basis of the current report. Survival was determined by the Kaplan-Meier method.

RESULTS

At the time of initial presentation, 19 patients had primary tumors, 3 had locally recurrent disease, and 3 had metastatic disease. The most frequent anatomic sites for HPC were the extremities, the pelvis, and the head and neck, accounting for 80% of the total cases. The median followup (n = 25) was 49 months (range, 1 to 160 months). The two and five year overall survival rates (n = 25) were 93% and 86% respectively. The disease-specific survival was 86% at last followup. Patients undergoing complete resection (n = 16) showed a 100% median survival at 60 months.

CONCLUSIONS

At present, complete tumor resection for patients with conventional HPC is recommended. However, considering the favorable outcome in this disease, the authors caution against performing operations that may potentially cause loss of function or are limb threatening.

Sinonasal haemangiopericytoma-like tumour: a sinonasal glomus tumour or a haemangiopericytoma?

AIMS

Sinonasal haemangiopericytoma-like tumour is controversial with regard to its nosologic nature. This study aims to investigate its relationship with glomus tumour and haemangiopericytoma.

METHODS AND RESULTS

Six cases of sinonasal haemangiopericytoma-like tumours identified in our files were reviewed for clinicopathological features, and compared with five cases each of soft tissue glomus tumour and meningeal haemangiopericytoma. Immunohistochemical studies for muscle-specific actin, smooth muscle actin, desmin and CD34 were performed. Sinonasal haemangiopericytoma-like tumour demonstrated a uniform histological appearance with bland-looking short, spindly cells forming sheets and short fascicles. The tumour cells were interspersed with slit-like, round and ectatic blood vessels. Actin immunoreactivity was demonstrated in all six cases, although occasionally patchy. The histological appearance and immunohistochemical phenotype of sinonasal haemangiopericytoma-like tumour were very similar to and focally indistinguishable from glomus tumour. Meningeal haemangiopericytoma, in contrast, was characterized by high tumour cellularity, random nuclear orientation, presence of staghorn vasculature and lack of immunohistochemical evidence of myogenic differentiation.

CONCLUSIONS

We conclude that sinonasal haemangiopericytoma-like tumour is biologically close to or identical to glomus tumour, but is not related to haemangiopericytoma.

Orbital hemangiopericytoma and solitary fibrous tumor: a morphologic continuum

Solitary fibrous tumors (SFT) and hemangiopericytomas (HPC) are soft tissue tumors with known histologic and immunohistochemical overlap. A series of these tumors located in the orbit were analyzed in order to determine whether they could be re-classified based on currently recognized histologic criteria. Ten orbital spindle cell lesions, all of which were positive for CD34 antigen, were examined. Diagnostic criteria for SFT included a cytologically bland spindle cell lesion with variable cellularity and focal dense collagenization with diffuse, strong CD34 reactivity, while the criteria for HPC required a more monotonous cellular proliferation without significant variability in cellularity, a "staghorn" vascular pattern, minimal collagenization, and focal or absent CD34 staining. Tumors with typical histologic and immunohistochemical features of HPC or SFT were diagnosed as HPC and SFT, respectively. Those tumors with histologic or antigenic profiles not classic for HPC or SFT were defined as 'indeterminate.' Three lesions were classified as SFT and 1 tumor was diagnosed as HPC through use of the above-cited histologic criteria. All lesions showed positive staining of tumor cells with CD34 antigen in varying amounts and were negative for cytokeratin AE1-3, epithelial membrane antigen, CD68, and Factor XIIIa. One solitary fibrous tumor focally stained for S-100 protein and 1 hemangiopericytoma was focally positive for HHF-35. Of the 10 analyzed tumors, 6 were classified as 'indeterminate.' Furthermore, 1 lesion whose primary histology was that of an SFT recurred 9 years later with an appearance consistent with an 'indeterminate' lesion. Our results call into question the present histologic separation of HPC and SFT in the orbit. As in other sites, including deep soft tissue, these data suggest that SFT and HPC are 2 lesions whose morphologic features are best interpreted to exist along a continuum, rather than 2 lesions with distinctly defined histopathology.

True hemangiopericytoma of the nasal cavity

Two cases of nasal tumors with pericytic myoid differentiation are reported. The tumors occurred in a 77-year-old woman and a 60-year-old man as polypoid lesions covered by normal mucosa. Histologically, the tumors were composed of uniform short spindle or stellate cells with indistinct cell borders arranged in narrow and short fascicles. Numerous blood vessels of various sizes were common in both cases. The tumor cells of both cases stained intensely with anti-vimentin and anti-actin antibodies, but not with anti-desmin, CD34, or anti-high-molecular-weight caldesmon antibodies. Ultrastructural examination revealed well-developed actin thin filaments with dense bodies, subplasmalemmal plaques, intercellular junctions, and irregular discontinuous basement membranes. These histopathologic features suggest true pericytic differentiation of the tumors (true hemangiopericytoma), unlike soft tissue-type hemangiopericytoma. Generally, sinonasal hemangiopericytomas are subdivided into soft tissue-type hemangiopericytomas and true hemangiopericytomas identical to the cases presented here. Soft tissue-type hemangiopericytomas are frequently highly aggressive, whereas true hemangiopericytomas show localized benign behavior. Sinonasal true hemangiopericytomas should be strictly differentiated from soft tissue-type hemangiopericytomas.

Hemangiopericytoma in children and infants

BACKGROUND

Hemangiopericytoma (HPC) is a soft-tissue neoplasm most commonly seen in adults; only 5-10% of cases occur in children. Childhood HPC comprises two distinct clinical entities. In children older than 1 year, it behaves in a manner similar to adult HPC. Infantile HPC, however, although histologically identical to adult HPC, has a more benign clinical course. The reasons for these differences in the natural history of HPC are not well understood.

METHODS

The authors reviewed the clinicopathologic features of HPC as well as the treatment and outcomes of the 12 children (9 males and 3 females) treated for this disease at St. Jude Children's Research Hospital over a 35-year period.

RESULTS

At diagnosis, 9 patients were older than 1 year and 3 were younger than 1 year. Among the 9 older patients, tumors were most commonly found in the lower extremities (n = 5). One patient had been treated for acute lymphoblastic leukemia 15 years earlier. One patient had metastatic disease at diagnosis, and three had unresectable tumors. Two patients experienced objective responses to chemotherapy. Three patients died of disease progression. Among the three infants, two had unresectable disease at diagnosis, and both experienced excellent responses to neoadjuvant chemotherapy. In one case, the response of the tumor to chemotherapy correlated with maturation to hemangioma. All three infants are alive without evidence of disease.

CONCLUSIONS

HPC in children older than 1 year does not differ from adult HPC, and aggressive multimodality therapy is required. Infantile HPC, on the other hand, is characterized by better clinical behavior, with documented chemoresponsiveness and spontaneous regression, and requires a more conservative surgical approach. In some cases of infantile HPC, this benign behavior correlates with maturation to hemangioma.

Lipomatous hemangiopericytoma: a morphologically distinct soft tissue tumor

Hemangiopericytoma of soft tissue is a controversial pathologic entity. The relative nonspecificity of the characteristic branching capillary pattern and cytologic features of the constituent cells, in addition to the lack of a distinct immunohistochemical staining profile, has resulted in uncertainty and a lack of consensus regarding this subgroup of tumors. Notwithstanding the doubt surrounding this entity, a morphologically unique variant, designated lipomatous hemangiopericytoma, was reported in 1995. To our knowledge, there have been no further reports of these tumors since the original description. We describe a lipomatous hemangiopericytoma that arose within the thigh of a 41-year-old woman. The tumor presented as a slowly enlarging, minimally tender, pulsatile mass. The tumor was completely excised and was found to be composed of an admixture of typical hemangiopericytoma and predominantly mature adipose tissue. Unlike previous descriptions of this entity, the current example exhibited a full range of adipocyte differentiation, including many multivacuolated adipocytes of variable size with characteristic nuclear scalloping (lipoblast-like cells). The mitotic count was less than 2 per 10 high-power fields examined. The clinical course has been benign during the short follow-up period. We discuss the pathologic features, including the immunohistochemical staining profile and ultrastructural appearance of this distinctive tumor, and briefly discuss the relationship between hemangiopericytoma and solitary fibrous tumor of soft tissue, a neoplasm with many clinical and pathologic similarities.

Angiogenic histogenesis of stromal cells in hemangioblastoma: ultrastructural and immunohistochemical study

Controversy regarding the origin of characteristic stromal cells (SC) is responsible for the placement of hemangioblastoma as a single entity in the category of "tumors of uncertain histogenesis" in the current WHO classification of brain tumors. This subclassification of hemangioblastoma is, to a large extent, a consequence of a remarkable antigenic heterogeneity of SC demonstrated in many, often contradictory immunohistochemical studies. In contrast, most of the electron microscopic studies demonstrated a number of features indicating angiogenic nature of SC and, therefore, hemangioblastoma. This study reevaluated the histogenesis of SC, applying immunohistochemistry as well as electron microscopy and immunoelectron microscopy. Immunohistochemical studies confirmed most of the previous results indicating a very frequent expression of vimentin, S-100 protein, neuron-specific enolase, and cytokeratins. SC were less commonly immunoreactive for desmin, factor XIIIa, and Ricinus communis lectin receptors, and only occasionally for factor VIII and Ulex europeus lectin. They were negative for other markers of endothelial, neuronal, glial, neuroendocrine, and smooth muscle differentiation. Approximately 1% of SC showed Ki67 immunoreactivity, indicating their slight proliferative activity, consistent with the benign nature of the tumor. In contrast to the inconclusive results of the immunohistochemistry, electron microscopy demonstrated a clear relationship of SC to endothelial cells, smooth muscle cells, and pericytes. Occasional SC were found within the vascular lumina. SC often showed intracellular caveolae consistent with the formation of early capillary lumina. Moreover, occasional SC contained small Weibel-Palade bodies positive for factor VIII in immunoelectron microscopy. SC represent a heterogeneous population of abnormally differentiating mesenchymal cells of angiogenic lineage, with some morphological features of endothelium, pericytes, and smooth muscle cells. Occurrence of SC in hemangioblastoma could be related to a limited ability of angioformative stromal cells to develop an architecture of capillary lumina integrated with the vascular network of the tumor. Hemangioblastoma should be reclassified and included together with other vascular tumors of the central nervous system.

Role of electron microscopy in the evaluation of soft tissue neoplasms, with emphasis on spindle cell and pleomorphic tumors

The current significant role of transmission electron microscopy in the evaluation of soft tissue tumors when correlated with conventional histological and immunohistochemical studies is discussed for the following entities: myxofibrosarcoma, storiform-pleomorphic fibrosarcoma (malignant fibrous histiocytoma), and myofibrosarcoma; dermatofibrosarcoma protuberans; hemangiopericytoma; monophasic synovial sarcoma; extrarenal rhabdoid tumor; soft tissue perineurioma; and gastrointestinal stromal tumors, notably the so-called autonomic nerve variant.

Cutaneous vascular proliferation. Part II. Hyperplasias and benign neoplasms

This second part of our review about vascular proliferations summarizes the clinicopathologic features of the cutaneous vascular hyperplasias and benign neoplasms. Hyperplasias comprise a heterogeneous group of vascular proliferations that eventually show a tendency to regression. Angiolymphoid hyperplasia with eosinophilia is included within the group of hyperplasias because of its historical denomination and its reactive nature, probably as a consequence of an arteriovenous shunt, although usually the lesions do not regress. Pyogenic granuloma, bacillary angiomatosis, intravascular papillary endothelial hyperplasia, and pseudo-Kaposi's sarcoma qualify as vascular hyperplasias because they regress when the stimulus that initiated them is removed. Benign neoplasms form a large group of hemangiomas with distinctive clinicopathologic characteristics, although some of them are of recent description and may produce diagnostic difficulties. We classified cutaneous benign vascular neoplasms according to their cell lineage of differentiation, for example, endothelial, glomus cell, and pericytic differentiation. Subsequent categories are established according to the size of the involved vessels (capillaries, venules and arterioles, or veins and arteries) or the nature of the proliferating vessels (blood or lymphatic vessels). Capillary and cavernous hemangiomas have been the terms classically used to name the most common variants of benign vascular neoplasms (i.e., infantile hemangiomas), but they are not the most appropriate denominations for these lesions. First, these names are not contrasting terms. Furthermore, most of the socalled "cavernous" hemangiomas are not hemangiomas (neoplasms) at all, but venous malformations. The most important conceptual issue is that, at any point in time, a particular hemangioma has its own histopathologic pattern throughout the depth of the lesion. For these reasons, we classified hemangiomas into superficial and deep categories. Some of the lesions reviewed have been recently described in the literature, and they may histopathologically mimic lesions of Kaposi's sarcoma; these include targetoid hemosiderotic hemangioma, microvenular hemangioma, tufted hemangioma, glomeruloid hemangioma, kaposiform hemangioendothelioma, spindle-cell hemangioendothelioma, and benign lymphangioendothelioma. In each of these lesions, we update and emphasize those clinical and histopathologic features that are helpful for differential diagnosis with lesions of authentic Kaposi's sarcoma in any of its three stages of development (patch, plaque, or nodule).

The immunophenotypic spectrum of meningeal hemangiopericytoma: a comparison with fibrous meningioma and solitary fibrous tumor of meninges

Despite controversy regarding its histogenesis, meningeal hemangiopericytoma (HPC) is a well-defined clinicopathologic entity exhibiting high rates of recurrence and late extracranial metastasis. It must be distinguished from several benign neoplasms, particularly fibrous meningioma (FM) and solitary fibrous tumor (SFT). To determine the immunoprofile of HPC, we studied 27 meningeal examples, including 13 low-grade and 14 high-grade tumors. For comparison, 20 FMs and eight SFTs of the meninges were also evaluated. The immunotype of HPC included vimentin (85%), factor XIIIa (78%) in individual scattered cells, Leu-7 (70%), and CD34 (33%) in a weak, patchy pattern. Focal desmin and cytokeratin positivity was only occasionally encountered (20% each). The SFT shared a similar immunophenotype, except that CD34 expression (100%) was characteristically strong and diffuse. The FM characteristically expressed epithelial membrane antibody (EMA) (80%) and S-100 protein (80%); CD34 reactivity (60%) was patchy and weak. Both within and among all three tumor types, MIB-1 labeling indices varied widely. Specifically, they were unrelated to tumor grade in HPC. Significant reactivity for p53 protein was detected in 52% of HPCs, 17% of SFTs, and 5% of FMs. Meningeal HPC exhibits a distinct antigenic profile, one enabling the exclusion of other entities in nearly all cases. The rare expression of desmin or cytokeratin in HPC suggests either the occurrence of divergent differentiation or, less likely, the possibility that its distinctive morphology is but a phenotype shared by several types of meningeal sarcoma.

Orbital hemangiopericytoma: clinical and morphologic features

PURPOSE

To report the clinical and histopathologic features of orbital hemangiopericytoma.

METHOD

We review the clinical and histopathologic features in seven patients.

RESULTS

Ultrasonography, computed tomography, and magnetic resonance imaging defined the location and extent of the tumor in each patient but did not disclose pathognomonic features for the specific diagnosis of hemangiopericytoma. The predominating histopathologic feature of each tumor was a mixed pattern of ovoid cells and sinusoidal space formations. Five patients showed mild to severe cellular atypia; three had obvious pleomorphism and increased number of abnormal mitotic figures. Tumor cells disclosed cytoplasmic reactivity for vimentin but in five cases were negative for other immunologic markers. Six patients received surgical treatment with an attempt for total removal of the tumor; one had biopsy and radiation therapy. In two patients, radiation therapy was given in addition to tumor removal with orbital exenterations. Three patients died with recurrent and metastatic disease, and four patients are alive without tumor for a follow-up period ranging from 3 to 9 years.

CONCLUSIONS

Orbital hemangiopericytoma may behave as a malignant tumor, leading to local recurrence or metastasis, or both. Clinical and histopathologic findings should be considered jointly to evaluate the clinical course; histopathologic findings alone are not sufficient to predict the biologic behavior of this tumor.

Malignant glomus tumor: a case report and review of the literature

This report concerns a malignant glomus tumor, a rare soft tissue tumor that was examined immunohistochemically and ultrastructurally. It occurred in a 44-year-old male patient who had suffered from dull pain and stiffness in the right thigh for 10 months. Radiographic examination revealed a well-defined osteolytic lesion in the diaphysis of the right femur. Hypervascularity of the tumor was observed angiographically. Computed tomographic and magnetic resonance examinations showed an intramuscular mass invading the marrow space of the femur. Wide resection was performed after open biopsy. Histologically, round to polygonal tumor cells revealed a uniform appearance of round to ovoid nuclei with single large nucleoli and slightly eosinophilic cytoplasm, forming solid sheets of cells interrupted by vessels of varying size. A few mitotic figures and vascular invasion were observed. Immunohistochemically, vimentin and alpha-smooth muscle actin were stained intensely, and muscle actin was positive for tumor cells of the perivascular area. Tumor cells were negative for desmin, factor VIII-related antigen, S-100 protein, neurofilament, cytokeratin, and epithelial membrane antigen. Ultrastructurally, tumor cells were characterized by many cytoplasmic processes, pinocytotic vesicles, plasmalemmal dense plaques, and scattered microfilaments in the cytoplasm. Few cell junctions and focal basement membrane-like structures were observed. No recurrence or metastasis was noted 57 months after operation. This case was considered to be a malignant glomus tumor, that is, a glomangiosarcoma arising de novo.