"Hey! Whatever happened to hemangiopericytoma and fibrosarcoma?" An update on selected conceptual advances in soft tissue pathology which have occurred over the past 50 years.

Hemangiopericytoma and fibrosarcoma represented at one time two of the most common diagnoses in soft tissue pathology. Both terms are now largely extinct. This article will review the clinicopathologic, immunohistochemical and molecular genetic advances that have led to these changes, and review the pathologic features of a select group of soft tissue tumors previously classified as hemangiopericytoma or fibrosarcoma.

[Solitary fibrous tumor/hemangiopericytoma of central nervous system: a clinicopathological analysis of 60 cases].

Objective: To investigate the clinical manifestations, imaging features, clinicopathologic features, and differential diagnosis of solitary fibrous tumors/anginoblastomas (SFT/HPCs) originating in the central nervous system. Methods: Sixty cases of SFT/HPCs originating in the central nervous system were collected at Nanjing Jinling Hospital, from January 1, 2008 to December 31, 2016. The clinical data, imaging data, histomorphologic changes and immunohistochemical finding were analyzed in the sixty cases. Results: The 60 cases included 26 males and 34 females, aged 14 to 85 (median 49) years. The main clinical manifestations were headache, dizziness with nausea and vomiting. Radiologically, the tumors were large, enhancing, solid and cystic masses attached to the dura. Histopathologically, the neoplasms were composed of spindle cells with oval nuclei, inconspicuous nucleoli and moderate amount of eosinophilic cytoplasm arranged in fascicles with areas of hyalinized stroma, myxoid changes and a staghorn vascular pattern. Immunohistochemically, tumor cells of all cases were positive for vimentin (100.0%, 60/60), STAT6 (98.3%, 59/60), CD34 (61.7%, 37/60), and the tumor cells were typically positive for CD99, bcl-2, EMA and SSTR2 as well.Negative for S-100 protein, SOX10, E-cadherin, GFAP. Ki-67 index ranged from 1% to 50%. Forty cases were followed up for 6 to 82 months with average of 40 months, 30 patients were alive and 10 patients died. Conclusions: Central nervous system SFT/HPCs can be aggressive and relapses may occur several years after diagnosis. STAT6 is highly sensitive and specific for the diagnosis. Complete tumor resection is optional treatment followed by radiotherapy and chemotherapy. There is a correlation between the prognosis and the location of the disease, the histological grade, Ki-67 index, and fusion gene variants.

ß-catenin (CTNNB1) mutation and LEF1 expression in sinonasal glomangiopericytoma (sinonasal-type hemangiopericytoma).

Sinonasal glomangiopericytoma (SN-GPC) is an uncommon mesenchymal tumor with myoid differentiation. Recently, mutations in exon 3 of the gene coding for ß-catenin (CTNNB1) and its nuclear expression were discovered in SN-GPC. ß-catenin protein is a key regulatory molecule of the canonical Wnt signaling pathway. The expression of ß-catenin target proteins is not well characterized in SN-GPC. We examined three SN-GPCs by immunohistochemistry and CTNNB1 mutation analysis. All cases expressed nuclear ß-catenin. We identified CTNNB1 exon 3 mutations in two analyzable cases. Lymphoid enhancer-binding factor 1 (LEF1), a protein downstream from ß-catenin, was also expressed in all cases. Our results further characterized the activation of the Wnt signaling pathway caused by CTNNB1 exon 3 mutation and suggest the utility of LEF1 immunohistochemistry in the differential diagnosis of SN-GPC.

Solitary fibrous tumour/haemangiopericytoma of the spinal cord. / Tumor fibroso solitario/hemangiopericitoma de la médula espinal.

Solitary fibrous tumours/haemangiopericytomas (SFT/HPC) are fibroblastic mesenchymal neoplasms that harbour a genetic fusion of NAB2/STAT6. There are few reported cases in the central nervous system (CNS), of which spinal tumours are minority. We present a case of a 63-year-old woman with progressive paraparesis and a sensory level of T6. On the MRI we detected an intradural extramedullary lesion on T9-T10. We performed a laminectomy with an intraoperative ultrasound study in which we observed a heterogeneous lesion with an infiltrating pattern affecting the medulla at several points, and resection of the lesion. Immunohistological findings revealed positivity for vimentin, CD34 and STAT6; Ki-67 was 2%. A final diagnosis of SFT/HPC with SFT phenotype was made. SFT/HPC of the CNS is a rare neoplasm that should be taken into account in the differential diagnosis of these kinds of lesions, as clinical and MRI findings often lead to errors in diagnostic approach. The support of intraoperative ultrasound can assist in surgical decision-making.

[Solitary fibrous tumor/hemangiopericytoma of central nervous system: a clinicopathologic analysis of 71 cases].

Objective: As solitary fibrous tumor (SFT) and hemangiopericytoma (HPC) share the same molecular genetics features, the 2016 WHO classification of central nervous system (CNS) tumors had created the combined term SFT/HPC and assigns three grades. This study aims to investigate the clinicopathologic characteristics, diagnosis, differential diagnosis and prognosis of CNS SFT/HPC. Methods: Seventy-one cases of CNS SFT and HPC were retrospectively reclassified and studied. Histopathological, immunohistochemical and imaging features were analyzed. The follow-up data were analyzed. Results: There were 37 male and 34 female patients. The median age was 48 years (range, 3-77 years). Twelve cases (17%) were WHO grade Ⅰ, 26 (37%) were WHO grade Ⅱ and 33 (46%) were WHO grade Ⅲ. Microscopically the tumor could show traditional SFT phenotype, HPC phenotype or mixed phenotype. Immunochemically, 97%(69/71) were positive for STAT6, with 96%(66/69)showing diffuse strong staining. Approximately 90% were diffusely positive for bcl-2, CD99 and vimentin. The expression rate of CD34 decreased with increasing tumor grade, and the mean expression rate was 78%. SSTR2a was variably expressed in 10% (7/71) of cases including one case showing strong cytoplasmic staining. A few cases expressed EMA, CD57 and S-100 focally. The Ki-67 index ranged from 1% to 50%. Thirty four patients were followed up for 8-130 months; 12 patients(35%)had recurrences, and two (6%) had liver metastases. Conclusions: CNS SFT/HPC is relatively uncommon. There was significant morphological overlap or transition between different grades. STAT6 is a specific marker for the diagnosis of this tumor. Surgical resection is the preferred treatment. WHO grade Ⅱ and Ⅲ SFT/HPC show rates of local recurrence and systemic metastasis, with liver being the most common site of extracranial metastasis.

[Solitary fibrous tumors and hemangiopericytomas of the meninges: Immunophenotype and histoprognosis in a series of 17 cases]. / Tumeurs fibreuses solitaires et hémangiopéricytomes des méninges : immunophénotype et évaluation du grade histopronostique dans 17 cas.

INTRODUCTION: The 2007 World Health Organization (WHO) classification of tumors of the central nervous system distinguishes meningeal hemangiopericytomas (HPC) from solitary fibrous tumors (TFS). In the WHO classification of tumors of soft tissue and bone, those neoplasms are no longer separate entities since the discovery in 2013 of a common oncogenic event, i.e. the NAB2-STAT6 gene fusion. A shared histopronostic grading system, called "Marseille grading system", was recently proposed, based on hypercellularity, mitotic count and necrosis. We evaluated the immunophenotype and histoprognosis in a retrospective cohort of intracranial HPC and TFS. METHODS: Fifteen initial tumors and 2 recurrences were evaluated by immunohistochemistry for STAT6, CD34, EMA, progesterone receptors and Ki67. The pronostic value of the WHO and the Marseille grading systems was tested on 12 patients with clinical follow-up. RESULTS: Initial tumors were 11 HPC and 4 SFT. STAT6 and CD34 were expressed in 16/17 tumors, EMA and progesterone receptors in 2 and 5 cases, respectively. The Ki67 labelling index was 6.25% in HPC and 3% in SFT. Half of the tumors recurred between 2 years and 9 years after initial diagnosis (mean time 5 years). No statistical difference in the risk of recurrence was associated with either grade (WHO or Marseille), in this small cohort. CONCLUSION: The diagnosis of HPC and TFS is facilitated by the almost constant immuno-expression of STAT6, and this justifies their common classification. The high rate of recurrence implies a very long-term follow-up because the current grading systems do not accurately predict the individual risk.

Intravascular Myopericytoma of the Plantar Region: Case Report and Discussion of the Probable Origin From a Cutaneous Vascular Malformation.

Myopericytoma is a perivascular myoid neoplasm of skin and soft tissues characterized by numerous thin-walled blood vessels surrounded concentrically by round to spindle myoid tumor cells, which shows α-smooth muscle actin and h-caldesmon coexpression and commonly negativity for desmin. These tumors arise predominantly in extremities of adult patients with benign clinical course. Based on the architectural pattern, there are various histologic variants as classical-solid myopericytoma, hemangiopericytoma-like myopericytoma, angioleiomyoma-like myopericytoma, myofibroma-like myopericytoma, hipocelular fibroma-like myopericytoma, intravascular myopericytoma, cellular immature myopericytoma, and malignant myopericytoma. The authors report a case that fully satisfies the morphological and immunohistochemical criteria for intravascular myopericytoma, which plantar location is not previously described in the literature. In addition, the authors discuss about its possible development from a preexistent cutaneous vascular malformation.

[Diagnostic value of STAT6 immunohistochemistry in solitary fibrous tumor/meningeal hemangiopericytoma].

OBJECTIVE: To investigate the diagnostic role of STAT6 immunohistochemistry in solitary fibrous tumors (SFT)/meningeal hemangiopericytomas (HPC). METHOD: Evaluated the expression of STAT6, vimentin, CD34, EMA, PR, S-100, CD56, GFAP and Ki-67 in a cohort of 37 SFT/meningeal HPC, 30 meningiomas and 30 schwannomas by immunohistochemistry staining. RESULTS: All SFT/meningeal HPC demonstrated nuclear positivity for STAT6, and the proportion of positive tumor cells ranged from 60% to 95%, with no significant difference cases.Vimentin was strongly positive in all cases. CD34, EMA and PR positivity was found in 32 cases, 1 case and 4 cases, respectively.S-100 protein, CD56 and GFAP were negative; Ki-67 labeling index was 1%-8%. However, the meningiomas and schwannomas were negative for STAT6. CONCLUSIONS: STAT6 is a relatively specific biomarker for SFT/meningeal HPC, and may be used in the diagnosis and differential diagnosis of SFT/meningeal HPC, especially for the atypical cases, and allows the precise pathologic diagnosis of SFT/meningeal HPC.

Differential Diagnosis of Meningeal SFT-HPC and Meningioma: Which Immunohistochemical Markers Should Be Used?

Meningeal solitary fibrous tumors-hemangiopericytomas (SFT-HPC) and meningiomas can be difficult to distinguish on histologic examination. STAT6 immunohistochemistry (IHC) is a reliable diagnostic marker of SFT-HPCs. Recently, GRIA2 has also been reported to be a diagnostic marker of SFT-HPC, although no extensive data are available for meningeal SFT-HPCs yet. The aim of this study was to test their diagnostic performance in a large cohort of SFT-HPCs and meningiomas. IHC analyses for GRIA2 and STAT6 were performed on tissue microarrays containing 76 SFT-HPCs and 181 meningiomas. Results were compared with previous data with ALDH1 and CD34. Two different anti-STAT6 antibodies were tested: SC-20 polyclonal and YE361 monoclonal antibody. Ninety-six percent of meningeal SFT-HPCs but no meningioma displayed nuclear STAT6 positivity. With SC-20 antibody, concomitant cytoplasmic staining for STAT6 was observed in >50% of all cases, including meningiomas. However, using YE361 antibody, cytoplasmic staining was absent, and nuclear signal intensity was stronger leading to better interpretation of STAT6 IHC. GRIA2 was positive in 84% of SFT-HPCs and in 16% of meningiomas. STAT6 had excellent sensitivity (96%) and specificity (100%), ALDH1 and GRIA2 had same sensitivity (84%), but ALDH1 and CD34 had better specificity than GRIA2 (97% and 96% vs. 84%, respectively). For the differential diagnosis of SFT-HPCs versus meningiomas, the best diagnostic approach is to perform STAT6, followed by ALDH1 and CD34 in the case of uncommon STAT6-negative cases. Because of meningioma positivity, GRIA2 seems less useful in this indication.

Meningeal Hemangiopericytomas and Meningomas: a Comparative Immunohistochemical and Genetic Study.

BACKGROUND: The meningeal hemangiopericytoma (MHPC) is a vascular tumor arising from pericytes. Most intracranial MHPCs resemble meningiomas (MNGs) in their clinical presentation and histological features and may therefore be misdiagnosed, despite important differences in prognosis. MATERIALS AND METHODS: We report 8 cases of MHPC and 5 cases of MNG collected from 2007 to 2011 from the Neuro-Surgery and Histopathology departments. All 13 samples were re reviewed by two independent pathologists and investigated by immunohistochemistry (IHC) using mesenchymal, epithelial and neuro-glial markers. Additionally, we screened all tumors for a large panel of chromosomal alterations using multiplex ligation probe amplification (MLPA). Presence of the NAB2-STAT6 fusion gene was inferred by immunohistochemical staining for STAT6. RESULTS: Compared with MNG, MHPCs showed strong VIM (100% of cases), CD99 (62%), bcl-2 (87%), and p16 (75%) staining but only focal positivity with EMA (33%) and NSE (37%). The p21 antibody was positive in 62% of MHPC and less than 1% in all MNGs. MLPA data did not distinguish HPC from MNG, with PTEN loss and ERBB2 gain found in both. By contrast, STAT6 nuclear staining was observed in 3 MHPC cases and was absent from MNG. CONCLUSIONS: MNG and MHPC comprise a spectrum of tumors that cannot be easily differentiated based on histopathology. The presence of STAT6 nuclear positivity may however be a useful diagnostic marker.

Myopericytoma tumor of the glans penis.

Myopericytoma is a low grade spindle cell neoplasm largely occurring in skin. We describe the first reported case of a penile myopericytoma. Histologically, the penile tumor was composed of a perivascular proliferation of tumor cells with ovoid shaped nuclei and abundant eosinophilic cytoplasm. Immunohistochemically, the tumor was reactive for markers of smooth muscle differentiation and vascular differentiation. The tumor was noted to be negative for BRAF by immunohistochemistry and wild-type upon gene sequencing using SnaPshot. Our finding serves to expand the anatomical distribution of myopericytoma and broadens the spectrum of primary mesenchymal neoplasms that may be encountered in the penis.

Sinonasal haemangiopericytoma: histomorphology and differential diagnoses.

A 39-year-old female presented with a fleshy nasal polyp occluding the left nasal cavity, associated with haemopurulent discharge. Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) scans of the paranasal cavities revealed a large polypoid tumour arising from the left middle turbinate and obstructing the left maxillary sinus ostium. However, no bony or intracranial involvement was identified. A biopsy revealed a tumour with small blue round cell morphology. The tumour cells showed diffuse strong membranous CD99 positivity and patchy CD34 positivity. Ancillary cytogenetic tests for the EWSR1 and SS18/SYT gene translocations were negative. In view of the non-invasive nature of the tumour and the low cell proliferative index (Ki-67) of 5%, a medial maxillectomy resection was performed. The resection revealed additional areas with spindle-cell morphology and focal haemangiopericytic vasculature. The tumour continued to show immunoreactivity to CD99 and CD34, as well as Smooth Muscle Actin (SMA) and Muscle Specific Actin (MSA). The overall findings are in keeping with a sinonasal haemangiopericytoma. With clear surgical resection margins, the patient is on routine follow-up and is currently disease-free.

Rapidly progressing left atrial hemangiopericytoma.

Cardiac hemangiopericytoma is a rare soft tissue tumor. We describe a case of hemangiopericytoma in the left atrium, which was diagnosed as myxoma preoperatively. A 70-year-old woman was admitted with heart failure. An echocardiogram showed a large myxoma-like mass in the left atrium, herniating into the left ventricle; therefore, an emergency operation was performed. Histological examination revealed a malignant hemangiopericytoma. The patient's postoperative course was uneventful, but she died due to a local recurrence 4 months after the operation.

[Sinonasal-type haemangiopericytoma: a case report]. / Sinonazal tip hemanjioperisitom: bir olgu sunumu

Sinonasal-type hemangiopericytomas, which comprise less than 0.5% of all sinonasal neoplasms, arise unilaterally in the nasal cavity as polypoid masses with a mean diameter of about 3 cm. A 34-year-old female patient was admitted due to nasal obstruction and epistaxis. A polypoid mass covered with intact mucosa that originated both from the right inferior concha and lateral nasal wall was detected by nasal endoscopy. The tumor, extending from the oropharynx to the nasopharynx, was measured as 3,5x3x2 cm. Although exhibiting characteristic histopathological features and typical clinical symptoms, this case with unexpected immunohistochemical findings can provide a viewpoint on the nature of this kind of tumors.

[Solitary fibrous hemangiopericytoma of atypical location: importance of immunohistochemical study]. / Tumor fibroso solitario hemangiopericitoma de localización atípica: importancia del estudio inmunohistoquímico.

BACKGROUND: The rare cutaneous solitary fibrous tumor was initially described in the thoracic cavity in relation to the pleura and subsequently been associated with other serous membranes. It has been described in other extraserosal locations including the skin. Knowledge of its existence along with fairly typical histological features and the immunohistochemical expression pattern with intense positivity for CD34 allow the increasing diagnosis of this condition, which suggests that these cases were not previously diagnosed as such. CLINICAL CASE: We report the case of a 43 year-old male with a painless nodule in the first left finger pad clinically suggestive of pyogenic granuloma or nodular melanoma, which was diagnosed by excisional biopsy and immunohistochemical study as a solitary fibrous tumor. DISCUSSION: Only 11 cases of cutaneous solitary fibrous tumor have been published in the following locations: head, cheek, thigh, chest, back and nose. Our work describes the first case of cutaneous solitary fibrous tumor in the hand. The solitary fibrous tumor derived from mesenchymal cells expresses CD34 and hence its presentation in any location. In our case it was in the hand. It explains the problems encountered in the clinical differential diagnosis with other tumors as nodular melanoma, pyogenic granuloma, giant cell tumor of tendon sheath, fibroma, benign peripheral nerve sheath tumors, etc. As we consider the histology, differential diagnosis should be made with other tumors that also express CD34. CONCLUSIONS: Solitary fibrous tumors derived from mesenchymal cells express CD34 and hence its presentation in any location. In our case it was in the finger pad.

Antecedentes: el tumor fibroso solitario es un tumor poco común. Anteriormente se suponía que afectaba sólo la cavidad torácica, en especial la pleura; posteriormente, se relacionó con otras membranas serosas y se observó en diversas localizaciones extraserosas, entre ellas la piel. El conocimiento de este tumor, junto con el aspecto histológico característico y el patrón de expresión inmunohistoquímica con intensa positividad para CD34 permiten que cada vez se diagnostique con mayor frecuencia. Caso clínico: se comunica el caso de un varón de 43 años de edad con un nódulo indoloro en el pulpejo del primer dedo izquierdo, que sugería clínicamente un melanoma nodular o granuloma piógeno. Mediante biopsia excisional y estudio inmunohistoquímico se diagnosticó como tumor fibroso solitario. Discusión: hasta la fecha se han publicado 11 casos de tumores fibrosos solitarios cutáneos, localizados en cabeza, mejilla, muslo, pecho, espalda y vestíbulo nasal. El caso que se comunica constituye la primera lesión de estas características que afecta la mano. El diagnóstico clínico diferencial del tumor fibroso solitario incluye otros tumores como: melanoma nodular, granuloma piógeno, tumor de células gigantes tenosinovial, fibroma y tumor de vaina de nervio periférico benigno. En cuanto a la histología, se planteó el diagnóstico diferencial con otras neoplasias que también expresan CD34. Conclusiones: el tumor fibroso solitario deriva de células mesenquimatosas y expresa CD34, lo que explica su aparición en cualquier localización, como en este caso, que fue en el pulpejo del quinto dedo.

MR imaging of intracranial hemangiopericytomas.

OBJECTIVE: To describe the MR features of primary intracranial hemangiopericytomas (HPCs) on conventional imaging, diffusion and MR spectroscopy and aim to determinate distinguishing features from meningiomas. METHODS: From 2006 to 2012, seven patients with pathologically confirmed primary intracranial HPCs were included. The clinical data, conventional MR findings (n=7), DWI features (n=7) and MR spectroscopy (n=5) were retrospectively analyzed. ADC values of the HPCs (n=7) were measured on ADC map and were compared with that of contralateral normal white matter. RESULTS: Of the seven HPCs, four were anaplastic HPCs (WHO grade III) and three were HPCs (WHO grade II). MR pattern consisted in lobulated or irregular margin tumors in all cases with cross-leaf growth on both side of the falx in two cases. The lesions showed mainly iso signal (n=4) on T1 WI and heterogeneous high signal (n=5) on T2 WI. Heterogenity was mainly related to intra tumoral hemorrhage (n=4), and proeminent intratumoral flow voids (n=3). Marked heterogeneous enhancement (n=5) with dural tail (n=4) was noted. All tumours showed significant peritumoral edema. ADC values of the tumor tissue component range between 0.638 and 1.50×10(-3)mm/s(2) (average = 1,02). Three grade II HPCs showed higher values compared to normal parenchyma ADC (range between 0.772 and 0.930×10(-3)mm/s(2) with average of 0.830), whereas grade III HPCs showed either equal (three cases) or decreased ADC values (one case). MRS showed in all cases markedly increased Cho with lip/lac peak, decreased Cr and almost absent NAA. High mI peak with large glutamine/glutamate were noted in the three grade II HPCs. CONCLUSION: Conventional MR pattern when combined with DWI and MRS findings are highly suggestive of HPC and appear valuable data to differentiate HPCs from meningiomas.

Malignant fat-forming solitary fibrous tumor (so-called "lipomatous hemangiopericytoma"): clinicopathologic analysis of 14 cases.

Fat-forming solitary fibrous tumor is a rare variant of solitary fibrous tumor (SFT). Generally regarded as benign, very few fat-forming SFTs with malignant histologic features have been reported. Here, we report 14 histologically malignant fat-forming SFTs to better characterize this subset. Seven patients were female and 7 were male, with ages ranging 20 to 93 years (median, 57 y). Five tumors were located in the lower limb, 3 in the trunk, 3 in abdominopelvic locations, 2 in the head and neck region, and 1 in the upper limb. The tumor size ranged from 3.4 to 20 cm (median, 8.6 cm). Histologically, all exhibited at least focal hypercellularity; 12 tumors had mitoses >4/10 high-power fields (range, 2 to 37; median, 8), 12 showed at least moderate atypia, and 8 showed necrosis. It should be noted that 7 tumors contained only mature adipose tissue, whereas 5 contained multivacuolated lipoblasts and 2 had areas resembling atypical lipomatous tumor (ALT). Immunohistochemically, CD34 and CD99 were positive in most cases (11 of 14 and 8 of 10, respectively); MDM2 and CDK4 were both negative in all 4 cases tested (including both tumors with ALT-like areas). Follow-up data from 10 cases (median duration, 47.5 mo; range, 5 to 76) showed 2 patients with multiple metastases (both to lung and bones, and 1 each to breast and to soft tissue), both of whom died of disease. In conclusion, fat-forming SFTs exhibiting malignant histologic features have potential for aggressive behavior. The presence of lipoblasts and/or ALT-like areas, although described in some "benign" examples of fat-forming SFT, seems much more common in the malignant subset and may prompt a careful search for morphologic evidence of malignancy in any case of fat-forming SFT.

[Primary malignant solitary fibrous tumor/hemangiopericytoma of the parotid gland]. / Tumor fibroso solitario maligno primario/hemangiopericitoma de la glándula parótida

Solitary fibrous tumor (SFT) was first described in the pleura by Lietaud in 1767; later in 1870, Wagner described the localized nature of this type of tumor and Klemperer and Rabin classified pleural tumors into two types: diffuse mesotheliomas and localized mesotheliomas. Recent years have seen the redefinition of this neoplasm, due to better technology; it is now proven that this neoplasm may have multiple different extrapleural origins including the head and neck regions. This diversity of locations is related to the particular mesenchymal histogenesis of SFT which allows its development from very unusual sites such as the salivary glands (SGs). In this particular site, this neoplasm is very infrequent and most of reported cases refer to benign disease, with just one case informed so far of primary malignant SFT.

[Solitary fibrous tumor of the abdomen. A rare neoplasm of vascular origin]. / Tumor fibroso solitario abdominal. Una rara neoplasia de origen vascular.

Solitary fibrous tumor (formerly known as hemangiopericytoma) is a rare soft tissue neoplasm, most frequently arising from the retroperitoneum and lower extremities. We present two cases of retroperitoneal solitary fibrous tumors diagnosed after surgical removal. We provide a literature review showing the basic clinical, pathologic and therapeutic features of these tumors.

Hemangiopericytoma-solitary fibrous tumor of the eyelid.

The authors report a rare case of hemangiopericytoma-solitary fibrous tumor of the eyelid. A 35-year-old male presented with approximately 1-year history of a painless and slow growing mass on his right lower eyelid, which rapidly grew in size over the last few months. The size of the lesion and the location resulted in secondary mechanical ectropion at presentation. The tumor was excised and was found to be a "hemangiopericytoma-solitary fibrous tumor" based on both histopathological and immunohistochemical examinations. Immunohistochemically, the tumor was positive for CD34 and Vimentin but negative for S100 protein and smooth muscle actin. Although initial tumor removal was complete, the patient required a subsequent operation for his residual ectropion. Despite the lesion being large at presentation, surgical intervention resulted in good functional and cosmetic outcome.