Ultrastructure of myopericytoma: a continuum of transitional phenotypes of myopericytes.

The authors report the ultrastructural characteristics of myopericytoma, a recently described variant of perivascular (pericytic) tumors, mainly with regard to their myopericytic cells and vessels. Myopericytes range between pericytes and vascular smooth muscle cells (SMCs) in a morphologic continuum. The principal findings of the intermediate phenotypes are (1) elongated or annular morphology with processes of varying length and thickness (usually long and thin); (2) a continuous, irregularly thickened and zonally duplicated basement membrane; (3) heterocellular "peg and socket" junctions with neighboring endothelial cells, and scarce specialized junctions between myopericytes; (4) numerous micropinocytotic vesicles, whether continuous or forming focal rows; (5) abundant thin microfilaments, grouped in bundles with dense bodies and adhesion plaques; (6) poorly developed synthetic system (RER and Golgi); (7) pseudointracellular bodies formed by invagination of basement and plasma membranes, with numerous endocytic vesicles; and (8) zones of cytoplasmic rarefaction near micropinocytotic vesicles and intracellular organelles. The ultrastructure of myopericytes therefore makes it possible to distinguish them from pericytes, SMCs, and fibroblast/myofibroblasts, which is useful for myopericytoma diagnosis. The main pattern of the vessels, with perivascular concentric and multilayered growth of myopericytes (a thick wall in contrast to a small lumen) and lack of elastic material, also supports an intermediate form between pericytic and muscular microvasculature. The presence of myopericytes more similar to SMCs and of hemangiopericytoma-like vessels concurs with transitional forms with angioleyomyoma and true hemangiopericytoma, histogenetically representing a morphologic continuum for the perivascular tumors.

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.

[Sinonasal-type hemangiopericytoma: a clinicopathologic analysis of 6 cases].

OBJECTIVE: To study the clinicopathologic features, histologic diagnosis and differential diagnosis of sinonasal-type of hemangiopericytoma (SNTHPC). METHODS: The clinical, radiographic and pathologic findings of 6 cases of SNTHPC were analyzed. Immunohistochemistry and electron microscopy were performed on selected examples. RESULTS: Amongst the 6 patients studied, 4 were males and 2 were females. The age of patients ranged from 56 to 71 years (mean = 60.5 years old). The commonest clinical presentation was nasal obstruction and/or epistaxis. Other symptoms could include increased nasal secretion, eyeball pain, decreased visual acuity, increased tear secretion and headache. The tumor involved nasal cavity and/or paranasal sinuses. Gross examination showed polypoid tumor masses, brownish fleshy tissue or whitish tumor tissue fragments. Histologically, the tumor showed a mixture of diffuse, fascicular, storiform, reticulated and whorled growth patterns. The tumor cells were spindle-shaped and possessed clear to eosinophilic cytoplasm. Mitotic figures were rarely seen. The intervening vasculature was characteristically thin-walled, with focal hyalinization changes and rarely the staghorn pattern. Immunohistochemical study showed that the tumor cells expressed vimentin (6/6), smooth muscle actin (5/6) and CD34 (3/6). Electron microscopy demonstrated the presence of intracytoplasmic myofilaments. The tumor cells were linked together by primitive cell junctions. In general, the histologic diagnosis of SNTHPC was difficult, and only 1 case had the correct initial pathologic diagnosis made. Follow-up data were available in 5 patients and 2 of them had local recurrences. CONCLUSIONS: SNTHPC is a low to intermediate grade soft tissue tumor with pericytes differentiation. Correct diagnosis relies on detailed pathologic assessment and application of ancillary investigations.

Low grade malignant peripheral nerve sheath tumour: varied cytological and histological patterns.

BACKGROUND: A small number of malignant peripheral nerve sheath tumours (MPNSTs) are low grade, and the nature of these low grade tumours has never been systematically assessed. AIMS: To describe the clinicopathological, immunohistochemical, and ultrastructural features of low grade MPNST and to discuss the main differential diagnoses. METHODS: Four cases of low grade MPNST were studied, including one coexistent with neurofibromatosis type 1. The tumours were analysed with respect to nuclear atypia, cellularity, nuclear enlargement, hyperchromasia, mitotic rate, and necrosis. Immunohistochemistry was performed by standard techniques, and an ultrastructural study was performed on one tumour. RESULTS: The ages of the patients ranged from 32 to 72 years (mean, 58). Two were male and two were female. Three tumours occurred in the deep tissue, including one in the retroperitoneum, and one was located in the dermal and subcutaneous tissue. The maximum diameters of the tumours ranged from 3.5 to 8.0 cm. Microscopically, all tumours showed moderate hypercellularity, an increased nuclear to cytoplasmic ratio, and hyperchromasia, but exhibited varied growth patterns, including those that were atypical neurofibroma-like, low grade fibromyxoid sarcoma-like, low grade epithelioid, and haemangiopericytoma-like. All tumours showed immunoreactivity for S-100 protein and vimentin. CONCLUSIONS: These findings suggest that careful clinical and histological evaluation, along with S-100 protein immunostaining, are essential for the accurate diagnosis of low grade MPNST.

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.

[Contribution of immunohistochemistry and electron microscopy for the diagnosis of meningeal hemangiopericytomas. 15 case reports]. / Apport de l'immunohistochimie et de la microscopie électronique dans le diagnostic des hémangiopéricytomes méningés. A propos de 15 cas.

Meningeal hemangiopericytomas (HPC) are rare CNS tumors with a pour prognosis compared to meningiomas. In order to define diagnosis criteria, we performed an immunohistochemical and ultrastructural study in respectively 15 and 5 meningeal HPC. The following antibodies anti-KL1, EMA, vimentin, CD34, factor VIII, alpha-smooth actin, estrogen and progesteron receptors (RE, RP) were used in paraffin embedded sections whereas anti-NCAM and E-cadherin antibodies were used on frozen sections when available. We can differentiate meningeal HPC from meningioma because of a complete lack of immunostaining with epithelial markers as well as with NCAM antibody or RE and RP receptors. Besides a positivity with CD34 and alpha-smooth actin antibodies was always observed even focally in HPC. On the other hand, solitary fibrous tumor showed a strong and diffuse positivity with anti CD34 and anti-vimentin antibodies. Electron microscopy can be helpful in some instances showing membrane basal-like substance and absence of desmosomes.

Fine-needle aspiration cytology of hemangiopericytoma: A report of five cases.

BACKGROUND: Hemangiopericytoma (HPC) is a relatively rare neoplasm, accounting for approximately 2.5% of all soft tissue tumors. Its histopathology has been well documented but to the authors' knowledge reports regarding its fine-needle aspiration (FNA) cytology rarely are encountered. In the current study the authors report the cytologic findings in FNA specimens from nine confirmed cases of HPC and attempt to correlate the cytologic features with the biologic outcomes. METHODS: FNA was performed with or without radiologic guidance. Corresponding sections of tissue were reviewed in conjunction with the cytologic preparations. RESULTS: Nine FNAs were performed in 5 patients (3 men and 2 women) with an age range of 38-77 years (mean, 56 years). Two lesions were primary soft tissue lesions arising in the lower extremities; seven were recurrent or metastatic lesions from bone (one lesion), kidney (one lesion), pelvic fossa (one lesion), lower extremities (two lesions), trunk (one lesion), and breast (one lesion). All aspirates were cellular and were comprised of single and tightly packed clusters of oval to spindle-shaped cells aggregated around branched capillaries. Basement membrane material was observed in 6 cases (67%). The nuclei were uniform and oval, with finely granular chromatin and inconspicuous nucleoli in all cases except one. No mitotic figures or areas of necrosis were identified. A correct diagnosis of HPC was made on one primary lesion and all recurrent or metastatic lesions. CONCLUSIONS: HPCs show a spindle cell pattern in cytologic preparations and must be distinguished from more common spindle cell lesions. The presence of branched capillaries and abundant basement membrane material supports a diagnosis of HPC. Immunohistochemistry and electron microscopy performed on FNA samples may be helpful in the differential diagnosis. FNA is a useful and accurate tool with which to confirm recurrent or metastatic HPC; however, prediction of the biologic behavior of HPC based on cytologic features is not feasible. Cancer (Cancer Cytopathol)

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.

Polypoid dermal hemangiopericytoma: a case report.

A polypoid dermal lesion with histologic, immunohistochemical, and ultrastructural features of hemangiopericytoma is described. Such tumors, arising in the dermis, are exceptionally rare, and whereas the tumor bears some resemblance to meningioma-like tumors of the skin and the well-recognized animal counterpart, canine hemangiopericytoma, it is histologically distinct.

Hemangiopericytoma of the liver: immunohistochemical observations, expression of angiogenic factors, and review of the literature.

PURPOSE: We describe an unusual case of a hemangiopericytoma in the liver of a child, review the literature, and characterize the tumor by immunohistochemistry and electron microscopy. We study the expression of basic fibroblast growth factor (bFGF) and of vascular endothelial growth factor (VEGF) in the tumor. MATERIALS AND METHODS: Clinical history and pathology were reviewed; sections of the tumor were studied by histology, electron microscopy, and immunohistochemistry using antibodies directed towards factor-XIIIa, HAM-56, bFGF and VEGF, among others. RESULTS: The expression of VEGF resembled that of "proliferating" hemangiomas; however, despite being markedly elevated in the urine, bFGF could not be unequivocally detected in the tumor. A subpopulation of factor XIIIa positive cells was identified, similar to the "interstitial" cells of the cellular hemangiomas of infancy. The nature and function of these cells remains speculative. CONCLUSIONS: Hemangiopericytomas are rare in the liver. When arising in this location in a child, they may clinically resemble a hemangioma, may express angiogenic factors in a similar fashion, and should be considered in the differential diagnosis.

Congenital hemangiopericytoma/infantile myofibromatosis: radical surgery versus a conservative "wait and see" approach.

Infantile/congenital hemangiopericytoma, although sharing many similar histological features with adult hemangiopericytoma, has a much better prognosis. Nevertheless, most cases described in the literature were pursued by radical surgery with or without adjuvant chemotherapy. We describe a neonate who presented with a huge mass in the right gluteus, 6 x 5 x 4 cm, and a small ventral abdominal mass. The masses were confirmed on biopsy according to light microscopy, immunohistochemistry, and electron microscopy as congenital hemangiopericytoma. They shrank spontaneously within 2 weeks and vanished within 2 months. We present a hypothesis that masses appearing in the neonatal period with this histology and with no life-endangering pressure on vital organs should routinely be dealt with conservatively.

Solitary fibrous tumor of the spinal cord.

We report a case of primary solitary fibrous tumor occurring in the intramedullary thoracic spinal cord in a 47-year-old man. The tumor predominately consisted of spindle cells separated by abundant collagen; a few areas of hemangiopericytomatous morphology were also present. The diagnosis was confirmed by immunohistochemistry and electron microscopy. The tumor was reactive to vimentin and CD34 but was negative for glial fibrillary acid protein (GFAP), S-100, smooth muscle actin, epithelial membrane antigen, HMB-45, myelin basic protein, and keratin; ultrastructural examination showed fairly undifferentiated cells within a collagenous matrix, few tight junctions, and sparse extravascular basement membrane. The occurrence of this tumor within the spinal cord parenchyma and in other extraserosal sites emphasizes the current belief that solitary fibrous tumors arise from mesenchymal tissues and are not restricted to the pleura and other serosal surfaces. Furthermore, solitary fibrous tumor is an entity that must be considered in the differential diagnosis of spindle cell central nervous system neoplasms.

Infantile myofibromatosis with hemangiopericytoma-like features of the tongue: a case study including ultrastructure.

We report a case of an infantile myofibromatosis with hemangiopericytoma-like features arising in the tongue of a 5-month-old female infant. Many authors now classify neoplasms as infantile myofibromatosis that were previously called infantile hemangiopericytoma. The ultrastructural features of our tumor illustrate its biphasic nature and provide a possible explanation for its histogenesis. Infantile myofibromatosis, including those diagnosed as infantile hemangiopericytomas, rarely arise in any intraoral location. Despite the generally good prognosis associated with these neoplasms, complete surgical excision is recommended to avoid recurrences.

Hemangiopericytoma of the skull base and Collet-Sicard syndrome: a case report.

Hemangiopericytoma (HP) is a mesenchymal tumor that originates from the pericytes of the capillary walls. This is a rare neoplasm, particularly in the head and neck; the skull base is involved exceptionally. We report a case of a large HP located in the jugular foramen. The last four cranial nerves were involved, causing a Collet-Sicard syndrome associated with facial palsy. Only one case of HP and Collet-Sicard syndrome is reported in the literature. The clinical course of the disease is described, emphasizing the long period of elapsed time between onset of the complaints and the final diagnosis. Diagnostic procedures and immunohistochemical evaluation are analyzed, along with the possible differential diagnosis with other pathological processes that more frequently involve the jugular foramen.

Non-paraganglioma jugular foramen lesions masquerading as glomus jugulare tumors.

Pulsatile tinnitus, hearing loss, lower cranial nerve deficits, and radiographic evidence of a vascular lesion of the jugular foramen have been considered diagnostic of a glomus jugulare tumor. Angiographic evidence of a blood supply from the external carotid artery system, including the ascending pharyngeal artery, further substantiates this diagnosis. This diagnostic algorithm for tumors of the jugular fossa is usually followed by either a surgical exenteration of a presumed glomus jugulare tumor via an infratemporal fossa approach or radiation therapy in selected patients. Pre-treatment biopsy of such lesions is typically not done, nor is it recommended widely in the literature. As demonstrated in this report, a number of lesions, including hemangiopericytoma and extramedullary plasmacytoma presenting in the jugular foramen can mimic glomus jugulare tumors in all aspects of their clinical and radiographic presentation. Omission of a pre-treatment biopsy can lead to a treatment plan appropriate for glomus tumors but suboptimal for these rare pathologic entities. A pre-treatment biopsy of lesions of the jugular foramen by exploratory tympanotomy or postauricular mastoidotomy provides a pathologic diagnosis on which to base treatment of lesions of the jugular foramen, without adding substantial morbidity or decreasing the chances of cure.

Sinonasal hemangiopericytoma.

Sino-nasal hemangiopericytomas are rare indolent mesenchymal tumors which slowly invade local tissue. Electronmicroscopy and immunohistochemical techniques may be necessary to differentiate hemangiopericytomas from other sarcomatous tumors. Differentiation between malignant and benign tumors poses a difficult task, therefore clinical correlation as well histological confirmation is necessary to establish a diagnosis. Due to the low incidence of distant metastasis and low mortality, surgery consisting of wide local excision is usually curative.

Hemangiopericytoma of the tongue in a 12-year-old child: ultrastructural and cytogenetic observations.

We report a case of hemangiopericytoma arising from the tongue of a 12-year-old child. Ultrastructurally, tumor cells revealed discontinuous basal lamina, intermediate-type intercellular junctions, subplasmalemmal thickenings, and smooth muscle-type cytoplasmic filaments. In addition, occasional oligocilia and test tube-like inclusions were observed. Karyotypic analysis of the tumor cells revealed two balanced translocations that have not been reported previously in pediatric solid tumors: one involved chromosomes 1 and 3, t(1;3)(p22;q21), and the other involved chromosomes 7 and 12, t(7;12)(p22;q13). This is the first report of cytogenetic aberrations in a pediatric hemangiopericytoma. Correlation with genetic findings in adult hemangiopericytomas suggests that the chromosome 12q13 rearrangement might be of particular importance.

A case of malignant hemangiopericytoma: an immunohistochemical and ultrastructural study.

We report one case of malignant hemangiopericytoma which started with a tumor in the lower jaw and multiple nodules in the lung. The tumor quickly metastasized to the brain and chemotherapy was not at all effective. Hemangiopericytoma is generally diagnosed by its histological characteristics. Recently, however, electron microscopy and immunohistochemical methods have been used for its diagnosis. In our case, electron micrograph showed the growth of hemangiopericytoma cells around immature endothelial cells. In addition, the tumor cells reacted positively only with anti-vimentin antibodies, and the endothelial cells in the tumor tissue were positive for antifactor VIII antibodies. The observed features were consistent with the characteristics of hemangiopericytoma.