Solitary fibrous tumors of soft tissue. A clinicopathologic and immunohistochemical study of 12 cases

Primary gastrointestinal stromal tumor in the retroperitoneum

Gastrointestinal stromal tumor (GIST) is the most frequent non-epithelial neoplasm in the gastrointestinal tract. GIST has received much attention both for its clinical significance and biological nature, while the retroperitoneal condition identical to GIST has been rarely described. Presented herein is a case of GIST arising from the retroperitoneum in a 67-year-old man. The solid tumor measuring 4 cm was uncovered in the retroperitoneum, between the abdominal aorta and inferior vena cava, on computed tomography. The patient underwent surgical excision of the tumor. Histological examination showed proliferating spindle cells in the clearly demarcated tumor; immunoreactivity for Kit and CD34 in tumor cells confirmed the diagnosis of GIST. The histological origin of GIST is suggested to be gastrointestinal pacemaker cells, because they share specific immunoreactivity for CD117/Kit, which is also relevant to pathogenesis of GIST. The present case was a rare primary GIST in the retroperitoneum with typical immunopathological features.

Myopericytoma of the oral cavity

BACKGROUND

Myopericytoma is a rare mesenchymal neoplasm of pericytic cells demonstrating myoid differentiation. The lesion typically arises within the subcutaneous tissue of the extremities. We report a case that, to the best of our knowledge, is the first case of myopericytoma involving the soft tissue of the oral cavity.

METHODS

A 36-year-old woman had a 5-mm sessile, whitish-pink, firm tongue nodule. The patient underwent excisional biopsy, and histopathologic examination as well as immunohistochemical analysis were performed.

RESULTS

The differential diagnosis by histologic analysis included solitary fibrous tumor, myofibroma, glomus tumor, and myopericytoma. The results of immunohistochemical analysis, when combined with the histologic features, led to a diagnosis of myopericytoma.

CONCLUSIONS

Applying strict morphologic criteria and appropriately selective immunohistochemical markers will help to distinguish myopericytoma in the oral cavity.

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 tumor with pseudo-lipoblasts involving the sublingual gland: report of a case and review of the literature

Solitary fibrous tumors (SFTs) are mesenchymal neoplasms uncommonly occurring in the salivary glands. In rare instances, SFTs can contain mature fat, atrophic fat, or vacuolated cells previously termed 'pseudo-lipoblasts', which may be misinterpreted as a feature of malignancy. We report an unusual tumor with pseudo-lipoblasts occurring in the sublingual gland. The tumor exhibited a prominent hemangiopericytic pattern, bland cytology, and immunohistochemical and morphologic features consistent with that of an SFT. A review of 15 cases of SFTs of the salivary glands is presented. Emphasis is laid upon the histologic differential diagnosis and the clinical features of these tumors.

Clinicopathological findings in a case series of extrathoracic solitary fibrous tumors of soft tissues

BACKGROUND

Solitary fibrous tumors (SFT) represent a rare entity of soft tissue tumors. Previously considered being of serosal origin and solely limited to the pleural cavity the tumor has been described in other locations, most particularly the head and neck. Extrathoracic SFT in the soft tissues of the trunk and the extremities are very rare. Nine cases of this rare tumor entity are described in the course of this article with respect to clinicopathological data, follow-up and treatment results.

METHODS

Data were obtained from patients' records, phone calls to the patients' general practitioners, and clinical follow-up examination, including chest X-ray, abdominal ultrasound, and MRI or computed tomography.

RESULTS

There were 6 females and 3 males, whose age at time of diagnosis ranged from 32 to 92 years (mean: 62.2 years). The documented tumors' size was 4.5 to 10 cm (mean: 7 cm). All tumors were located in deep soft tissues, 3 of them epifascial, 2 subfascial, 4 intramuscular. Four tumors were found at the extremities, one each at the flank, in the neck, at the shoulder, in the gluteal region, and in the deep groin. Two out of 9 cases were diagnosed as atypical or malignant variant of ESFT. Complete resection was performed in all cases. Follow-up time ranged from 1 to 71 months. One of the above.mentioned patients with atypical ESFT suffered from local relapse and metastatic disease; the remaining 8 patients were free of disease.

CONCLUSION

ESFT usually behave as benign soft tissue tumors, although malignant variants with more aggressive local behaviour (local relapse) and metastasis may occur. The risk of local recurrence and metastasis correlates to tumor size and histological status of surgical resection margins and may reach up to 10% even in so-called "benign" tumors. Tumor specimens should be evaluated by experienced soft tissue pathologists. The treatment of choice is complete resection followed by extended follow-up surveillance.

Malignant Solitary Fibrous Tumor of the Kidney: Report of a Case and Comprehensive Review of the Literature

Renal solitary fibrous tumors (SFTs) have been reported infrequently. We report a 76-year-old man with a left renal mass that had previously been shown radiographically to be stable, but was now growing. Grossly, the mass measured 12 cm, was poorly circumscribed, and invaded beyond the renal capsule. Approximately 10% of the neoplasm consisted of haphazardly arranged spindle cells admixed with dense collagenous bands, which is typical of benign SFT. However, the remainder of the mass was composed of pleomorphic, spindled sarcoma cells with frequent mitoses and foci of necrosis. Immunohistochemically, we observed CD34 labeling in the benign SFT component with loss of expression in the sarcomatous component, focal labeling for Bcl-2 protein in both areas, and absence of labeling for cytokeratin, renal cell carcinoma marker, S100 protein, CD117, and muscle markers in both areas. To our knowledge, this is the first reported case of malignant renal SFT, likely representing transformation from a histologically documented benign SFT component.

Sclerosing Paraganglioma

Nineteen cases of a distinctive variant of paraganglioma characterized by extensive collagen deposition resulting in a pattern of growth that resembled an invasive malignant neoplasm are described. The patients were 3 men and 16 women, 32 to 69 years of age (mean, 50.5 years). The tumors were located in the carotid body region, parapharyngeal region, and mediastinum. Tumor size ranged from 2 to 6 cm in greatest diameter. Grossly, the tumors were described as rubbery to firm, tan-red, and with extensive areas of sclerosis. Histologic examination showed nests and cords of tumor cells separated by broad bands of fibrous tissue. The tumor cells ranged from round to polygonal with abundant cytoplasm to elongated spindle cells with scant cytoplasm. Nuclear cytomegaly was present focally enhancing the atypical appearance of the tumor cell population in 17 cases. Mitoses were sparse (<1 x 10 HPF), and there was no evidence of necrosis in any of the cases. Foci of vascular and perineural invasion were present in 2 and 4 cases, respectively. The most striking morphologic feature was the presence of irregular cords and bands of hyalinized fibrous tissue that compartmentalized the lesion into irregular nests, islands, or cords of tumor cells, imparting them with an infiltrative appearance. All the tumors showed positive immunostaining for chromogranin, synaptophysin, and monoclonal neuron specific enolase. S-100 protein stains identified a sustentacular cell network, whereas cytokeratin AE1/AE3 was negative in all cases. Clinical follow-up in 14 cases, ranging from 2 months to 20 years (mean follow-up, 6.6 years) showed evidence of local recurrence in 2 cases and the development of a separate tumor in the contralateral neck in 1 case. The remainder of patients were free of recurrence or metastasis following simple local excision. Because of the prominent sclerosis, a diagnosis of an invasive malignant neoplasm was initially considered in the majority of cases. Sclerosing paraganglioma should be included in the differential diagnosis of sclerosing lesions of the head and neck region and mediastinum. Appropriate immunohistochemical stains may be of aid for establishing the correct diagnosis.

Myxoid solitary fibrous tumour of the axilla

Mostly occurring in pleura, solitary fibrous tumour is an unusual soft tissue neoplasm. Solitary Fibrous Tumour with abundant myxoid stroma represents a rare morphologic subtype of the already uncommon tumour. We report a myxoid solitary fibrous tumour of the soft tissue in a 42-year-old man. The patient presented with a large, movable, nontender mass at the right axilla. The MRI showed a well-defined tumour with increased signal after gadolinium injection. During surgery, the mass was found to be closely associated with the axillary vein. The tumour was completely excised. Pathological and immunohistochemical examinations identified the mass as a myxoid solitary fibrous tumour. The patient was free of tumour recurrence at 18-month follow-up. The rare tumour in an uncommon location makes the diagnosis difficult. Complete excision and long-term follow up are recommended.

Low-grade malignant perineurioma (perineurial sarcoma) of soft tissue: a potential diagnostic pitfall on fine needle aspiration

A case of low-grade malignant perineurioma presenting as a mass in the thigh is described. The patient was a 76-year-old woman with an enlarging painful mass on her right lateral thigh over the past 2 months. Thorough clinical and radiological studies did not reveal any evidence of tumor elsewhere. The patient underwent fine needle aspiration of the mass, which revealed pleomorphic spindle cells in small clusters or dispersed as single cells within myxoid stroma, cytologically consistent with a high-grade sarcoma. At surgery, the tumor was found to be entirely confined within the muscle. Grossly, the tumor measured 6.5 cm in greatest diameter and showed a gray-white fleshy cut surface that was well circumscribed but unencapsulated. Histologic examination showed a highly cellular spindle cell proliferation embedded within myxoid stroma. The tumor cells showed mild to moderate nuclear pleomorphism with minimal mitotic activity. No evidence of hemorrhage or necrosis was noted. The tumor irregularly invaded the surrounding skeletal muscle. Immunohistochemical studies showed weak membranous positivity for epithelial membrane antigen and focal cytoplasmic positivity for CD34; stains for smooth muscle actin, cytokeratin AE1/AE3, desmin, CD56, H-caldesmon, calponin, and S-100 protein were negative. Electron microscopy showed cells with thin, elongated cytoplasmic processes extending along connective tissue in a parallel, onion-like arrangement and prominent subplasmalemmal pinocytotic activity. The marked pleomorphism displayed on fine needle aspiration observed in this case can lead to a mistaken diagnosis of high-grade sarcoma resulting in unnecessarily aggressive management.

Tumor fibroso solitário do rim: descrição de caso

Apresentamos um caso de tumor renal num paciente de 27 anos de idade, que foi submetido a estudo de imagem por tomografia computadorizada e ressonância magnética. As características radiológicas da massa induziam para um diagnóstico de tumor renal maligno de origem intraparanquimatosa. No entanto, o estudo histopatológico revelou tumor fibroso solitário benigno originário da pelve e porção calicial do rim direito.

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.

Malignant mesothelioma of the tunica vaginalis testis: a case with a predominant sarcomatous component

We present a case of malignant mesothelioma (MM) of the tunica vaginalis testis. A 64-year-old man was referred for an operation on a right hydrocele that later proved to be a tumor during surgery. The tumor was malignant with a biphasic pattern of epithelial and sarcomatous components. The latter component was predominant. Cuboidal or columnar cells formed irregular tubular structures in the epithelial component. In contrast, spindle-shaped or polygonal cells formed intricate structures with stromal connective tissues in the sarcomatous component. Immunohistochemical staining revealed that the tumor was mesothelial in origin and positive for cytokeratin, vimentin, HBME-1 antigen and calretinin. In general, MM occur in the pleura or peritoneum; those originating in the tunica vaginalis testis are very rare and represent less than 5% of all MM. In addition, MM in the tissues usually consist primarily of an epithelial component. According to previous reports tumors with a predominant sarcomatous component are extremely rare. In general, a sarcomatous component predicts poor prognosis and our case does, in fact, deteriorate over time. Our case suggests that despite its low incidence, MM must be considered when a case is diagnosed as hydrocele testicle.

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.

Unusual Solitary Fibrous Tumors in the Central Nervous System: A Report of Two Cases

Solitary fibrous tumors (SFTs) are uncommon, and most are found in the pleura. Extrapleural SFTs are rare and have been found in the lung, pericardium, mediastinum, soft tissue of any site, and upper respiratory tract. SFTs of the central nervous system (CNS) are very rare. The biologic features are unknown and remain poorly understood from a clinical standpoint. Most neurosurgeons do not believe that SFTs can present as primary CNS neoplasms. Most SFTs are clinically benign and indolent, and recurrences after surgical excision are scarce. Because malignant transformation or metastasis has been reported, all SFTs should be treated as having malignant potential. Long-term follow-up is recommended. We report two cases, so that surgeons may recognize that this is an entity different from other spindle-cell CNS tumors.

Solitary fibrous tumor arising in the sphenoethmoidal recess: a case report and review of the literature

Recently, solitary fibrous tumors (SFTs) have been reported in the head and neck area, such as the nasal cavity, thyroid, salivary gland, etc. We present a rare case of SFT which arose from the sphenoethmoidal recess of the nasal cavity, penetrating into the sphenoid sinus, and which showed different intensities on magnetic resonance imaging (MRI) according to the occupied locations. T2 weighted magnetic resonance (MR) images showed low intensity in the nasal cavity, and iso-intensity in the sphenoid sinus. Enhancement with gadolinium contrast on T1-weighted images was more remarkable in the sphenoid sinus than in the nasal cavity. While the tumor in the nasal cavity showed abundant collagen and high cellularity in microscopic examination, numerous small vessels and dilated vascular spaces were remarkable in the tumor of the sphenoid sinus. MRI findings corresponded to pathological findings. We review SFTs in the head and neck area in the English literature.

[Solitary fibrous tumor -- report of two cases]

Solitary Fibrous Tumor is a rare neoplasm derived from mesenchymal cell. To achieve a diagnosis and to differentiate from others neoplasm immunohistochemical analysis is needed. The majority of these tumours are benign, and complete surgical resection remains the mainstay of therapy for both the benign and malignant variants. However, there are cases of local and distant recurrences, so patients should have a close follow-up and it is far incorrect to look at this lesion as definitely benign. The authors review clinical presentation, radiological features, histological findings, and treatment options for this tumor and report two clinical cases discussing the differences between them.

Solitary Fibrous Tumors of the Pleura: Surgical Outcome and Clinical Course

BACKGROUND

The aim of this study was to define more precisely the surgical outcome and clinical course of solitary fibrous tumors of the pleura.

METHODS

We conducted a retrospective review of the clinical records of patients who had undergone surgical resection for benign and malignant solitary fibrous tumors of the pleura during a 10-year period (1993 to 2003).

RESULTS

Sixty-three patients were enrolled in the study (men, 29; women, 34; mean age, 49.6 years). Thirty-six patients (57.1%) were symptomatic at the time of diagnosis. Resection was performed through a thoracotomy (n = 37), by means of video-assisted thoracoscopy (n = 22), or through a sternotomy (n = 4). Mass excision only was performed in 34 cases, and en bloc excision including adjacent structures was performed in 29 cases. Forty-four cases (69.8%) were benign and 19 (30.2%) were malignant. Local recurrences occurred in three cases and distant metastases in eight. Recurrences occurred only in malignancy. Symptomatic presentation and the impression of a nonpleural tumor by imaging study were found to be related to a malignant pathologic diagnosis. The radiologic impression of solitary fibrous tumors of the pleura was also related to mass excision only.

CONCLUSIONS

For malignant cases, complete surgical resection may be insufficient for the cure. Therefore, further study should be performed to define the role of preoperative and postoperative systemic treatment.

Usefulness of immunohistochemistry in delineating renal spindle cell tumours. A retrospective study of 31 cases

AIMS

To assess the usefulness of immunohistochemistry in delineating tumour diagnoses on a series of morphologically diagnosed renal spindle cell tumours (RSCTs).

METHODS AND RESULTS

Formalin-fixed paraffin-embedded tissues from 31 morphologically diagnosed tumours were reinterpreted in light of newly obtained immunohistochemical information. By morphology, six had originally been classified as sarcomatoid carcinoma, five as spindle cell tumour (NOS), four as sarcoma (NOS), three as leiomyoma, three as leiomyosarcoma, and one each as fibrous polyp, hamartoma, neurilemmoma, mesoblastic nephroma, medullary fibroma, angiomyolipoma, haemangiopericytoma, malignant rhabdoid tumour, malignant Triton tumour, and carcinosarcoma. The application of immunohistochemistry verified the original diagnosis in 18 cases (18/31, 58%), confirming the diagnosis of sarcomatoid renal carcinoma (4/6), leiomyoma (2/3), leiomyosarcoma (3/3), sarcoma (NOS) (2/4), carcinosarcoma (1/1), malignant rhabdoid tumour (1/1), malignant Triton tumour (1/1), fibrous polyp (1/1), mesoblastic nephroma (1/1), hamartoma (1/1), and angiomyolipoma (1/1). Different tumour designations were suggested in 13 cases (13/31, 42%), including carcinosarcoma, sarcoma (NOS), leiomyosarcoma, solitary fibrous tumour, monomorphic/biphasic angiomyolipoma, endometrial stromal tumour, and congenital mesoblastic nephroma.

CONCLUSIONS

Our data indicate that although morphology is most important in formulating the initial differential diagnosis, the addition of immunohistochemistry is vital in arriving at the correct classification of RSCTs.

Proliférations fibroblastiques et myofibroblastiques de l’enfance et de l’adolescence

Fibroblastic-myofibroblastic proliferations of childhood and adolescents form a clinical and morphologic spectrum from benign reactive processes and pseudosarcomas, to fibromatoses, to various types of sarcoma. The diagnosis is challenging because of clinical and morphologic similarities, lack of specific immunohistochemical markers for different types of fibroblastic-myofibroblastic tumors, and limited molecular genetic information. Careful attention to clinical, macroscopic, and histopathologic features permits classification in most cases. This review focuses on the pathologic features of fibroblastic-myofibroblastic tumors with a predilection for children and adolescents.

Cellular Angiofibroma

Cellular angiofibroma is a recently described histologically distinctive benign mesenchymal neoplasm composed of 2 principal components, the cellular spindle cell component and prominent stromal blood vessels. Cases in males have sometimes been called "angiomyofibroblastoma-like tumor." We describe a series of 51 cases of cellular angiofibroma to further characterize its clinicopathologic and immunohistochemical features. There were 26 women and 25 men, ranging in age from 22 to 78 years (mean 53.5, median 52 years). Men tended to be older than women. Tumor size ranged from 0.6 to 25.0 cm (overall median size 3.9 cm, median in women 2.7 cm, median in men 6.7 cm). Most common sites were the vulvovaginal region (22 cases) and the inguinoscrotal region (19 cases). Preoperative duration (known for 25 patients) ranged from 1 week to 5 years, with presentation as a painless mass, except for 1 case each with intermittent genital bleeding and a painful mass. Most lesions were located primarily in subcutaneous tissue. Most cases were grossly well marginated. Two cases showed foci of hemorrhage and 1 case showed foci of necrosis. Microscopically, 41 tumors were well circumscribed, and 2 tumors infiltrated into the surrounding tissue. All tumors consisted of bland, spindle-shaped cells, short bundles of wispy collagen and numerous small- to medium-sized thick-walled vessels. Intralesional fat was present in 12 cases (6 female and 6 male cases). Mild cytologic atypia (5 cases) and frequent mitoses (3 cases) were infrequent; significant nuclear atypia and abnormal mitoses were absent. By immunohistochemistry, 29 of 48 tumors (60%) expressed CD34, 10 of 48 (21%) SMA, 4 of 48 (8%) desmin, but none expressed S-100 protein. Follow-up information was available for 40 patients (range 4-168 months; mean 31.2 months) and no patient has developed recurrence or metastasis to date.

Solitary Fibrous Tumor of the Spinal Cord: Case Report and Review of the Literature

OBJECTIVE AND IMPORTANCE:

A solitary fibrous tumor (SFT) is a rare neoplasm of probable mesenchymal origin that was first reported in the pleura but can occur in different sites. Only six cases of SFT arising from the spinal cord have been reported.

CLINICAL PRESENTATION:

We report a case of primary SFT occurring in the thoracic spinal cord in a 64-year-old man with Brown-Séquard syndrome. Magnetic resonance imaging revealed an intradural mass at the level of T2–T3.

INTERVENTION:

Total T2–T3 laminectomies were performed. The tumor appeared to be adherent to the right lateral aspect of the cord but not attached to the meninges. On histological examination, the tumor exhibited spindle cell proliferation with abundant dense collagen but without a hemangiopericytomatous pattern. Immunohistochemically, the tumor cells were reactive with CD34 and vimentin only.

CONCLUSION:

We report a rare case of SFT occurring in the thoracic spinal cord. Histologically and immunohistochemically, we confirmed the diagnosis of SFT. Low signal intensity on T1- and T2-weighted images corresponded to the histological findings. When a spinal cord tumor exhibits a signal pattern similar to this, SFT should be included in the differential diagnosis. Because of the rarity of reports on this condition, the clinical manifestations and course of SFT of the spinal cord are unknown, and careful long-term follow-up is recommended.

Primary lung carcinoma metastatic to a solitary fibrous tumor

We report the case of a 78-year-old man with a 2 month history of newly diagnosed metastatic lung adenocarcinoma, who presented with a left gluteal soft tissue mass. Histological examination of the mass revealed a solitary fibrous tumor containing metastases from adenocarcinoma.

Solitary Fibrous Tumor of the Liver with Presenting Symptoms of Hypoglycemic Coma

We report a patient with solitary fibrous tumor of the liver, a rare fibrous neoplasm which to our knowledge has been reported in only 21 patients in the English literature. Most frequently, solitary fibrous tumors arise in the thoracic cavity, particularly in the pleura. Hypoglycemia has rarely been associated with these mesenchymal tumors. The presentation of this patient with hypoglycemic coma without preceding symptomatology, to our knowledge, has never been reported.

Disseminated malignant solitary fibrous tumor of the pleura

Solitary fibrous tumor (SFT) of the pleura typically forms a localized pleura-based mass, and most are benign. A rare case of disseminated malignant SFT of the pleura is reported. The patient was a 71-year-old man who presented with complaints of shortness of breath to his primary care physician. A diagnosis of malignant mesothelioma was suspected, based on clinical, radiological and needle biopsy findings. He was referred to our institution for surgery. An extrapleural pneumonectomy, encompassing all pleural masses, was performed. Gross examination of the resected specimen was remarkable for numerous masses, ranging in size from 0.2 to 13.5 cm, covering the majority of the visceral pleura. Histologically, the tumor was composed of short spindle cells admixed with variable proportions of collagenous stroma. There were great intra- and intertumoral heterogeneity in tumor growth pattern, cellularity, pleomorphism and mitoses. Histologically malignant areas were present in all of the masses examined. The neoplastic cells were diffusely and intensely positive for bcl-2. Most tumor cells were also strongly stained for CD34 and CD99. Staining for cytokeratin was negative. The tumor also revealed p53 over-expression. Thus, the histological and immunohistochemical features of the tumor were consistent with a disseminated malignant SFT. This report shows that SFT rarely presents with disseminated pleural involvement, and a panel with CD34, bcl-2 and cytokeratin are valuable for differentiating SFT from malignant mesothelioma and other malignant spindle cell neoplasms of the pleura.

[Solitary fibrous tumor. Two additional cases with urologic implications]

Solitary fibrous tumour is a well defined pathological entity originally described as a tumour of the pleura, but the occurrence of this neoplasm has increasingly been described at other sites. At present the development of these tumours is recognized as possible in virtually all anatomical sites. The rarity of this type of pathology has not allowed up to the present time clarification of the histogenesis, clinical behaviour, treatment and prognosis of these tumours. Differential diagnosis becomes important, especially in extra-thoracic sites so as not to mistake them for much more aggressive mesenquimal tumours. Two additional cases of this neoplasm are presented, one of them responsible for obstructive uropathy, accidentally found in a patient suffering renal trauma. The second tumour was located in the spermatic cord. A review of the theme is presented based on the available literature.

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.

Solitary fibrous tumor of the orbit: a clinicopathologic study of six cases with review of the literature

Solitary fibrous tumor of the orbit is a rare spindle cell neoplasm. There are 42 cases of solitary fibrous tumor of the orbit available in the literature. We present six more cases of orbital solitary fibrous tumors, which presented to our institute between 1999 and 2001. We highlight the need for clinical recognition of these tumors as a distinct entity and inclusion of this tumor in the etiological differential diagnosis of well-circumscribed orbital lesions presenting as unilateral proptosis in both children and in adults. The diagnosis may be suspected based on radiological features supported by histopathologic and immunohistochemical study. The strong CD34 immunoreactivity of this tumor supports its diagnosis. Complete surgical resection is the most important prognostic factor of this tumor.

Collagen-rich tumors of soft tissues: an overview

Although relatively common, soft tissue tumors frequently present diagnostic problems for practicing pathologists. Immunohistochemistry has facilitated the diagnosis of many mesenchymal tumors; however, there is considerable overlap in the staining profiles among cells demonstrating fibroblastic and myofibroblastic differentiation. It has been our experience that soft tissue tumors associated with abundant extracellular collagen deposition commonly cause problems in classification. One reason for this is that tumors displaying this morphology include representatives from different histogenetic families. Specifically, tumors exhibiting fibroblastic, myofibroblastic and even lipomatous differentiation may manifest as a densely collagenous mass. It is the purpose of this review to highlight these collagen-rich soft tissue tumors.

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.

Solitary fibrous tumor in the extremity: case report and review of the literature

A solitary fibrous tumor is a relatively unusual neoplasm first described as a distinctive tumor arising from pleura. Some reports have shown that solitary fibrous tumors also affect extrathoracic regions. The current study presents a literature review with four additional patients with solitary fibrous tumor arising from the extremities to clarify clinicopathologic features. The current four patients were two males and two females, ranging from 17 to 60 years of age. Magnetic resonance imaging scans of the current patients showed inhomogeneous low to intermediate intensity signal on T1-weighted images and inhomogeneous intermediate to high intensity signal on T2-weighted images. Histologically, the tumors were composed of a haphazard proliferation of spindle cells, although cellularity was variable in each case. Two of the four tumors showed hypercellularity of spindle cells with focally myxomatous or hyaline changes, whereas myxomatous patterns with scattered spindle cells throughout the specimens were observed in the other two tumors. Immunohistochemically, all four patients showed positive immunoreactivity for CD34, and two tumors showed focally positive immunoreactivity for bcl-2 protein. During the followup of 12 to 54 months, neither local recurrence nor distant metastasis was detected after wide resection. Examination of the literature and the current patients suggests that solitary fibrous tumors in the extremities are likely to have a malignant potential, although most patients have a benign clinical course. Local wide resection and careful long-term followup are necessary for patients with solitary fibrous tumor in the extremities.

Solitary fibrous tumor with malignant potential arising in sublingual gland

A rare case is described of a solitary fibrous tumor (SFT) with malignant potential arising in the sublingual gland. A 59-year-old man presented with a 4-month history of a slowly enlarging painless mass in the center of the floor of the mouth. The tumor was a well-demarcated, firm mass with a multicystic lesion. The tumor exhibited highly cellular areas of spindle cells with patternless architecture alternating with hypocellular areas. The tumor cells were positive for CD34 and bcl-2 as well as vimentin, and negative for epithelial, myogenic, neurogenic and histiocytic markers. The tumor cells formed multiple satellite nodules around dilated ducts in the multicystic lesion, indicating infiltrative growth. In addition, areas exhibiting higher cellularity with increased mitoses were noticed in the satellite nodules, although cellular atypia was not obvious. These findings led to a final diagnosis of SFT with malignant potential. There has been no recurrence or metastasis for 27 months after the surgery. Solitary fibrous tumor of the salivary gland must be differentiated from various spindle cell neoplasms including myogenic, peripheral nerve sheath, fibroblastic and fibro-histiocytic spindle cell neoplasms, hemangiopericytoma and myoepithelioma. In addition to characteristic morphological features, an immunohistochemical positivity for CD34 and bcl-2 may aid in the diagnosis of SFT.

Immunohistochemical comparison of gastrointestinal stromal tumor and solitary fibrous tumor

CONTEXT

The differential diagnosis of gastrointestinal stromal tumors (GIST) and solitary fibrous tumors (SFT) may be a diagnostic challenging because of overlapping clinicopathologic features. Many studies have shown consistent immunoreactivity for CD117 (c-Kit) in GIST. However, only a few studies have evaluated CD117 expression in SFT, and these studies have used an antibody from Santa Cruz Biotechnology. In non-GIST lesions, reactivity with this antibody has been shown to differ from that with a CD117 antibody from Dako Corporation. The immunoreactivity of SFT with the Dako CD117 antibody has not been reported. Conversely, CD99 is a marker for SFT, and its expression in GIST has not been evaluated.

OBJECTIVE

To study the immunohistochemical profiles of GIST and SFT to evaluate their diagnostic overlap.

DESIGN

We studied the immunoreactivity of 27 unequivocal GIST and 19 unequivocal extra-abdominal SFT for CD117, CD34, CD99, alpha-smooth muscle actin, vimentin, CD31, S100 protein, and muscle-specific actin. All antibodies, including CD117, were from Dako Corporation.

RESULTS

We found positive immunoreactivity for CD117 in 100% of GIST and none of SFT; for CD34 in 89% of GIST, and 100% of SFT; for CD99 in 89% of GIST and 100% of SFT; for alpha-smooth muscle actin in 48% of GIST and 31% of SFT; for vimentin in 89% of GIST and 90% of SFT; and for muscle-specific actin in 22% of GIST and none of SFT. None of the GIST or SFT showed immunoreactivity for CD31 and S100 protein.

CONCLUSIONS

The major difference between GIST and SFT was strong CD117 immunoexpression in all GIST and an absence of this expression in all SFT. With the exception of muscle-specific actin, the prevalence of immunoreactivity for the markers studied did not differ substantially between these 2 tumors. We conclude that GIST and SFT show distinctly divergent immunoprofiles with respect to CD117 and muscle-specific actin.

Immunohistochemical localization of endothelial cell markers in solitary fibrous tumor

Solitary fibrous tumor (SFT) is an uncommon tumor first reported in the pleura, but recently described in other tissues. CD34, which is expressed in hematopoietic stem cells, endothelial progenitor cells and vascular endothelial cells, is observed in most SFT and some investigators believe that its expression is a definitive marker of this tumor. In the present study, the expression of vascular endothelial cell markers, such as vascular endothelial growth factor receptor (VEGFR)-1 (flt-1), VEGFR-2 (flk-1/KDR), Tie-2 and c-Met, was examined in SFT to clarify the relationship between SFT and endothelial cells. By immunohistochemical staining of tumor cells from 26 patients, VEGFR-1 was detected in 24 (92%), VEGFR-2 in five (19%), Tie-2 in 14 (54%), and c-Met, a specific receptor of hepatocyte growth factor (HGF) in 23 patients (88%). Furthermore, VEGFR-3 (flt-4) immunoreactivity was detected in eight of 26 patients (31%). In contrast, VEGF, VEGF-C and HGF, which are ligands for the receptors, were not localized in the SFT cells. These findings indicate that most SFT may closely relate to vascular or lymphatic endothelial cells and the endothelial growth factors may contribute to the growth of SFT in a paracrine manner.

Neural fibrolipoma of the superficial peroneal nerve in the ankle: a case report with immunohistochemical analysis

This report presents a case of neural fibrolipoma arising from the superficial peroneal nerve in the ankle. A 28-year-old woman was referred with a soft tissue mass in the anterior aspect of the right ankle, which had been gradually enlarging for the past 10 years. Magnetic resonance imaging showed a mass lesion, measuring approximately 8 x 3 x 2 cm, with high to partially low signal intensity on both T1- and T2-weighted images. A band of low signal intensity within the lesion, which is indicative of coexistence with the tumor and the superficial peroneal nerve, could be detected on both T1- and T2-weighted images. The patient underwent an excisional biopsy. The specimen microscopically consisted of nerve bundles and fibro-fatty proliferation with abundant collagen fibers. Immunoreactivity for CD34 antigen antibody was detected in fibrous spindle cells. This is the first report to present an immunohistochemical profile of neural fibrolipoma. Neural fibrolipoma should be considered as a differential diagnosis when a lipomatous lesion is encountered in the foot or ankle as well as in the upper extremities.

Steroid hormone receptor in pleural solitary fibrous tumours and CD34+ progenitor stromal cells

Solitary fibrous tumours (SFT), originally described in the pleura, were subsequently recognized in numerous extrapleural sites. This suggests that a common stem cell, present in various organs and tissues, may be at the origin of SFT and that specific factors may be involved in the proliferation of such cells. Recently it has been described that steroid hormone receptors, progesterone receptors in particular, are expressed by extrapleural SFT. In addition, progesterone may participate as growth factor in many CD34(+) stromal neoplasms, which express low levels of the hormone receptors. The present study analysed the expression of androgen (AR), oestrogen (ER) and progesterone (PR) receptors in a series of 32 pleural SFT, 10 mesotheliomas and in reactive tissue of chronic pleuritis. ER and AR were never expressed by SFT or by chronic pleuritis, whereas PR were demonstrated in 2/16 "large" (>8 cm) and in 6/16 "small" (< or =8 cm) pleural SFT (all expressing CD34, bcl-2 and CD99). PR(+) SFT had a significantly higher proliferative activity (p = 0.04) (Ki-67 mean value 6.5%) and lower p27(kip1) (mean value 51.5%) expression than the PR(-) cases (Ki-67 mean value 3.81% and p27(kip1) mean value 57.86%). One of the cases expressing a high level of PR (80%) recurred 1 year after first surgery and the recurrence was PR(+) as well, but with a lower percentage of nuclear receptor expression (12%). In addition, in chronically inflamed subserosal tissue, a subpopulation of CD34(+) endothelial and interstitial dendritic cells was identified, which also expressed PR. These findings suggest that the CD34(+) submesothelial interstitial dendritic cells, activated during reactive processes, may be the stem cells that give rise to SFT, and that progesterone might participate in the growth of SFT through modulation of its specific receptors.

A case of solitary fibrous tumor of the parotid gland: review of the literatures

We report a rare case of solitary fibrous tumor of the parotid gland. A 47-year-old woman presented with a 3-year-history of left-sided subauricular swelling. Computed tomographic scans and magnetic resonance images revealed a well-defined and dumbbell-shaped mass, measuring about 30 mm in its greatest dimension, in the left parotid gland. Because the tumor occupied both superficial and deep lobes of the gland, she underwent total parotidectomy with preservation of the facial nerve. The microscopic finding showed short-spindle and ovoid cells arranged in a haphazard pattern with interspersed thin collagen fibrils. Immunohistochemically, the tumor cells were strongly positive for CD34, bcl-2 and vimentin, whereas stains for S-100, cytokeratin, smooth muscle actin, collagen type IV and CD117 (KIT) were negative. On the basis of these findings, the tumor was diagnosed as solitary fibrous tumor. Her post-operative course was uneventful, and she is currently free from disease 14 months after surgery. Diagnosis, clinical behavior and treatment of solitary fibrous tumor are reviewed from perusal of the literature.