Intracranial hemangiopericytoma: ultrastructural evidence of its leiomyoblastic differentiation

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.

Haemangiopericytoma presenting with acute intracerebral haemorrhage

Clinical presentation of brain tumour by acute haemorrhage is well known and occurs in around 5% of the cases. Haemangiopericytoma (HPC) is a richly vascularized tumour, but its clinical manifestation is most frequently related to tumour mass effect or seizures. We present the eighth case reported of a patient with acute intracerebral bleeding caused by HPC. Though HPC represents only about 2% of intracranial meningeal neoplasms it must be included in the differential diagnosis of intracranial haemorrhage.

Management of intracranial meningeal hemangiopericytomas: outcome and experience

Hemangiopericytomas represent rare intracranial tumors that have a tendency to recur locally and have the unique characteristic of giving extracranial metastases. Our current communication reviews a series of patients diagnosed with hemangiopericytoma who were treated in our facility. Eleven patients with a mean age of 51.2 years underwent follow-up for a mean time of 7.1 years. Their neuroimaging preoperative evaluation included plain skull X-rays, head CT scans, brain MRI, angiograms, and (1)HMRS. Preoperative embolization of the tumor was employed in 6/11 patients. All patients underwent craniotomy for tumor resection and postoperative radiation treatment was employed on all but one. Grade I resection was accomplished in 6/11 (54.5%), grade III in 4/11 (36.4%), and grade IV in 1/11 (9.1%). Local recurrence was detected in 3/11 (27.3%) at a mean period of 5 (range 2-7.5) years. Extracranial metastatic disease was documented in 4/11 (36.4%) patients at a mean of 4.9 (range 2.5-7) years after the initial diagnosis. The GOS score was: 7/11 (63.6%) scored 5, while 4/11 (36.4%) died at a mean time of 5.5 (range 3-8) years after the initial diagnosis. Intracranial hemangiopericytomas management requires aggressive surgical resection, postoperative radiation treatment, and extensive follow-up to rule out local recurrences and delayed extracranial metastases.

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.

Hemangiopericytoma of the central nervous system: a review of 94 cases

Ninety-four cases of central nervous system hemangiopericytoma (CNS-HPC) are reported. Hemangiopericytoma was found more commonly in men than in women. The mean age at diagnosis was 40.9 years for men and 47 years for women. The tumor was found throughout the entire CNS, usually superficially and closely related to the meninges. Based on multiple histologic variables, the original tumors were divided into differentiated (n = 67) and anaplastic (n = 27). Anaplastic HPC was characterized by the presence of necrosis and/or greater than five mitoses per ten 400x microscopic fields, and at least two of the following microscopic features: hemorrhage, moderate to high nuclear atypia, and moderate to high cellularity. For those patients known to be dead, median survival time was 144 months for differentiated HPC and 62 months for anaplastic HPC. Fifty-seven (60.6%) patients had one or more recurrences and metastasis developed in 22 (23.4%). Thirty-five of 56 patients with differentiated HPC had recurrence, while 22 of 26 patients with anaplastic HPC had recurrence. Bone, liver, lung, central nervous system, and abdominal cavity were the most common sites of metastasis. Postoperative radiotherapy and/or chemotherapy were significantly associated with increased patient survival time.

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

Since ultrastructural examination is often employed to assess controversial soft tissue tumors, it is important to be aware of the range of differentiation assumed by the tumor cells in hemangiopericytomas. For this purpose, 35 examples (10 localized to the central nervous system and 25 located peripherally) were examined ultrastructurally, and, of these, 20 cases were also studied immunohistochemically for the presence of intermediate filaments and muscle-specific actin. Based on cytologic characteristics evident by electron microscopy, tumor cell differentiation was classed as pericytic (32%), myoid (8%), nondescript (48%), fibroblastic (4%), and histiocytic (8%). Vimentin was the only intermediate filament expressed in the normal pericytes of human fetal and adult tissues and in the neoplastic pericytes of all of the hemangiopericytomas. Muscle-specific actin was present in normal pericytes, but only focally in two of the hemangiopericytomas. In various combinations basal lamina-like materials, cytoplasmic processes, cytoplasmic filaments, discrete basal lamina, and poorly formed intercellular junctions were the most frequently noted features of the tumor cells in hemangiopericytomas, whether central or peripheral, and they assist, along with the organizational relationship of tumor cells and capillaries, in distinguishing this lesion from other soft tissue sarcomas.

Antidesmosomal monoclonal antibody in the diagnosis of intracranial tumours

Immunocytochemistry has been applied extensively to the diagnosis of intracranial tumours, but meningiomas still present a diagnostic problem. However, desmosomes have been shown by electron microscopy to be present in meningiomas, and this distinguishes them from gliomas. This paper describes a new monoclonal antibody, 11-5F, against desmosomal proteins 1 and 2 (desmoplakins) and assesses its usefulness in the diagnosis of meningiomas and other intracranial tumours. A total of 74 surgically removed intracranial tumours were examined by fluorescent antibody staining with 11-5F on frozen sections. In addition, a panel of antibodies against cytokeratin, vimentin, glial fibrillary acidic protein, and S100 protein was used. 11-5F stained 30/30 meningiomas and 14/14 metastatic carcinomas but 0/30 gliomas, thus distinguishing meningiomas and metastatic carcinomas from gliomas. The distinction between meningiomas and metastatic carcinomas on the basis of intermediate filaments staining was more difficult because neither the anticytokeratin nor the antivimentin antibody was specific for either tumour type. This study emphasizes the value of antidesmosomal antibodies as an important adjunct to the diagnosis of intracranial tumours.

Capillary hemangioblastoma: histogenesis of stromal cells

The histogenesis of stromal cells in capillary hemangioblastoma has been the subject of debate. The light and electron microscopic studies of hemangioblastomas presented here showed pericytic and leiomyoblastic features in stromal cells. Cells cultured by the monolayer method showed similar features to those of the original tumors. Immunohistochemical studies for glial fibrillary acidic protein and factor VIII/von Willebrand factor indicated that stromal cells were antigenically distinct from astrocytes and endothelial cells. These findings suggest that stromal cells are closely related to pericytes and smooth muscle cells, and support Rhodin's speculation that pericytes serve as a precursor to smooth muscle cells.

Meningeal tumors of infancy and childhood

Seventeen meningeal tumors were examined for pathology with electron microscopy and immunohistochemistry including glial fibrillary acidic protein (GFAP), S-100 protein, muramidase, and factor VIII. These tumors included seven meningiomas, one hemangiopericytoma, three meningeal sarcomas (1 pleomorphic-cell type and 2 myxofibrosarcomas), two fibrous histiocytomas, and four malignant melanomas. Two of seven children with meningioma had a poor outcome despite the benign histological features of the tumor. S-100 protein was present in the two tumors. All three children with meningeal sarcoma had a rapid downhill clinical course, although the myxofibrosarcoma initially had a relatively benign histological appearance. The two children with fibrous histiocytoma did well despite the aggressive histological features. Muramidase was a good marker of such tumors. Because of the morphological difficulties associated with childhood meningeal tumors, both electron microscopy and immunohistochemistry can be of diagnostic benefit.

Immunohistochemical study of fibronectin in hemangioblastomas and hemangiopericytomas

Eight hemangioblastomas and two hemangiopericytomas were studied using indirect immunoperoxidase stains for fibronectin (FN) and glial fibrillary acidic protein (GFAP) in formalin-fixed, paraffin-embedded surgical specimens. Stromal cells in hemangioblastomas were GFAP-negative and showed variable FN expression, while GFAP-positive cells were FN-negative, thus suggesting that the stromal cells are not derived from astrocytes. Hemangiopericytoma cells were poorly to intermediately FN-positive. The origin of stromal cells is discussed in the light of their fine structure and the immunohistochemical stains with other cell markers.

Cellular haemangioma. Light and electron microscopic studies of two cases

Light and electron microscopic studies were conducted on the immature vascular tumors of two infants, containing various stages of differentiation of the blood vessels and both benign haemangioendotheliomas and haemangiopericytomas. We were able to confirm the existence of two kinds of hyperplastic, immature cells i.e. endothelial cells and pericytes in the same tumor. Presence of crystalloid inclusions in the endothelial cells and absence of the Weibel-Palade bodies, as well as a deficiency in factor VIII-related antigen and no tissue fibrinolytic activity, suggested that the endothelial cells in these lesions were immature. Electron microscopic studies appear more decisive in the diagnosis of heterogenous cellular vascular tumors than light microscopy and if available should be used to aid in the final diagnosis. The authors propose that the term cellular haemangioma would be more appropriate in describing this vascular entity.

Hemangiopericytoma of the orbit: a clinicopathologic study of 30 cases

The clinical and pathologic features of 30 orbital hemangiopericytomas were reviewed. An effort was made to determine the clincopathologic characteristics that may correlate with the biologic behavior. Histopathologic criteria evaluated included degree of cellularity, nuclear atypia, mitotic activity, tumor size, and the presence of hemorrhage and necrosis. Histopathologically, 16 tumors were classified as benign, five as borderline, and nine as malignant. Follow-up information was obtained in 27 cases (mean duration of follow-up period was five and one-half years). Eight tumors recurred (30 per cent). Five patients died, four with widespread metastases (15 per cent) and one of unrelated causes. Tumors that recurred or metastasized were distributed among all three histologic groups. The interval between the onset of symptoms and metastasis for three of the four lethal tumors was 31 years, 28 years, and 8 1/2 years; in the fourth case it was unknown. For the entire series, the five-year actuarial survival rate was 89 per cent. Although the number of cases is too small to serve as a basis for firm conclusions, the lack of unequivocal correlation between the histologic features and clinical behavior is consistent with the unpredictable behavior of this neoplasm, as concluded by other investigators. Because of the apparent circumscription of most of these tumors, complete surgical excision rather than exenteration is recommended. Metastasis usually develops late in the clinical course of the disease, indicating that long-term follow-up studies are required before a cure can be assumed.

Hemangiopericytoma: a light microscopic and ultrastructural study

An ultrastructural study of three cases of hemangiopericytoma showed cells partially or completely enveloped by well-formed basement membrane and basement membrane-like material. The cells exhibited prominent cytoplasmic filaments, some showing dense body formation, interdigitating cytoplasmic processes, and pinocytotic vesicles. A review of the literature revealed only 19 other cases of hemangiopericytoma studied by electron microscopy, and these included seven cases of meningeal origin ("angioblastic meningioma"). The most consistent feature seen in all but two cases was the presence of a basal lamina or basal lamina-like material either partially or completely surrounding tumor cells and separating endothelial cells from pericytes. The light microscopic diagnosis of hemangiopericytoma is difficult, and there is a tendency to append the diagnosis to a variety of other tumors with a prominent vascular pattern in which other specific diagnoses are not immediately evident. The presence, ultrastructurally, of well-developed basement membrane, myogenic type filaments, and pinocytotic vesicles in a tumor with light microscopic features suggestive of hemangiopericytoma would consolidate the diagnosis and usually eliminate diagnostic uncertainty.

Cellular angiomas of infancy: an ultrastructural study of two cases

Vascular tumors in infants may be clinically disfiguring, requiring surgical intervention. Some of these lesions are histopathologically worrisome, due to increased cellularity and mitotic activity. The interpretation of these lesions is hampered by a surfeit of terminology, although, regardless of the diagnostic name, they are clinically benign. Two such cellular angiomas are reported, one typical and one unusual case. Electron microscopy of both cases demonstrated a heterogeneous cellular composition, primarily endothelial cells and pericytes. In those light microscopic areas of diffuse growth, primitive vascular structures were resolved. Electron microscopy may be diagnostically useful in supporting the light microscopic impression of a vascular tumor.

Hemangiopericytoma of the spinal canal. Report of three cases

Hemangiopericytoma is a vascular neoplasm consisting of capillaries outlined by an intact basement membrane that separates the endothelial cells of the capillaries from the spindle-shaped tumor cells in the extravascular area. These neoplasms are found in soft tissues but have rarely been shown to involve the spinal canal. This is a report of three such cases. Surgical removal of the tumor from the spinal canal was technically difficult. A high risk of recurrence has been reported but in these three cases adjunctive radiotherapy appeared to be of benefit in controlling the progression of the disease. These cases, added to the six cases in the literature, confirm the existence of hemangiopericytoma involving the vertebral column with extension into the spinal canal. This entity should be included in the differential diagnosis of lesions of the spinal canal. The risk of intraoperative hemorrhage should be anticipated.

Dural mesenchymal chondrosarcoma. Case report

A dural mesenchymal chondrosarcoma is reported in a 19-year-old man. This tumor had features of angioblastic meningioma (meningeal hemangiopericytoma), by light microscopy. However, ultrastructurally this tumor could be distinguished from angioblastic meningioma, and its similarity to extracranial mesenchymal chondrosarcoma was confirmed.

Meningioma and intracranial hemangiopericytoma. A comparative electron microscopic study

Electron microscopic study of 2 intracranial hemangiopericytomas and 7 meningiomas revealed fundamental morphologic differences between the 2 neoplasms. The most significant finding in hemangiopericytoma was the presence of ultrastructure features suggesting leiomyoblastic differentiation. These included characteristic fusiform intracytoplasmic and submembranous dense bodies, abundant cytoplasmic filaments, elongated cells with blunt-ended nuclei and juxtanuclear polarization of organelles. This observation is considered highly significant as an indicator of the pericytic nature of this tumor. In addition, hemangiopericytoma cells sometimes were arranged in spirals around pools of basement membrane-like material, perhaps a manifestation of the biologic capability of the cells to synthetize such material. Meningioma cells displayed as their main feature an ability to produce surface membrane specializations including interdigitations, desmosomes, zonulae adhaerentes and gap functions. Sometimes the last 3 elements were linearly juxtaposed forming junctional complexes similar to those seen in certain epithelia. It is suggested that the characteristic whorls of meningioma are the result of cell interconnections arising from the specialized junctional attachments. Thus the distinctive morphology of the 2 neoplasms appears to derive from basic biologic properties of their elements.

The angioblastic meningioma: a reappraisal of the nosological problem. Light-, electron-microscopic, tissue, and organ culture observations

The validity of the concept of the angioblastic meningioma, now in dispute, was reexamined by reviewing 79 meningeal and angioblastic tumors of the central nervous system and by comparing the fine structural characteristics and in vitro evolution of 2 typical meningiomas and 1 intracranial hemangiopericytoma. While most tumors show the consistent features of either hemangiopericytoma or hemangioblastoma, there exist transitional forms between these tumors and typical meningioma. There is also a greater degree of morphological overlap at the electron microscopic level than has been recognized up till now. In view of these findings the concept of the angioblastic meningioma deserves to be retained as a generic term to include craniospinal hemangiopericytomas and transitional forms between hemangiopericytoma, hemangioblastoma and classic meningioma. It is postulated that all these tumors share a common origin from polyblastic mesenchymal cells originating in or derived from the meninges.