Extrathoracic Solitary Fibrous Tumors Research Articles

A Review of the Surgical Management of Extrathoracic Solitary Fibrous Tumors.

Extrathoracic solitary fibrous tumors (ESFTs) are rare low-to-intermediate grade spindle-cell neoplasms of pluripotent fibroblastic or myofibroblastic origin. This review explores prognostic factors in the management of ESFTs and provides guidance on optimal treatment regimens based on the current literature. Electronic searches were performed using MEDLINE, Embase, and the Cochrane library to identify studies on prognostic factors in the management of ESFTs published between January 1970 and June 2016. The literature search and review process identified 100 articles that were included in this review article. This included both surgical and nonsurgical studies on the management of ESFTs. Surgical excision with wide resection margins forms the mainstay of treatment and provides optimal long-term oncological outcomes. Large tumor size (>5 to 10 cm diameter), inadequate resection margins, malignant histologic features, dedifferentiation, and tumor location within the abdomen/pelvis are associated with adverse oncological outcomes. Radiotherapy may be used for preoperative tumor shrinkage and/or as adjuvant therapy in patients with malignant disease or incomplete surgical margins. Chemotherapy with molecular-targeted therapies has produced promising results and the results of further phase 2 trials are awaited. Routine long-term follow-up is essential for benign and malignant disease to enable early detection and treatment of recurrent disease.

Metastatic Patterns of Solitary Fibrous Tumors: A Single-Institution Experience.

The objective of our study was to evaluate the metastatic patterns and imaging features of solitary fibrous tumors (SFTs). This retrospective study included 139 patients with pathologically proven SFT, 49 of whom developed metastases. Electronic medical records and all available images were reviewed to record the pattern and imaging appearances of metastatic disease, and comparisons of thoracic SFTs and extrathoracic SFTs were also performed. Associations of metastatic spread were studied using univariate and multivariate Cox regression analyses. A total of 49 (35%) patients developed metastases at a median of 124 months (interquartile range [IQR], 66-195 months) after SFT diagnosis; 11 patients (8%) had metastases at presentation. Of these 49 patients, 40 patients died at a mean of 183 months after diagnosis. The associations with metastatic disease on univariate analysis were tumor size ≥ 10 cm (p = 0.01) and malignant pathology or mitotic count ≥ 4 per 10 high-power fields (HPF) (p < 0.001). Malignant pathology and a mitotic count of ≥ 4 per 10 HPF were also associated with metastatic disease on multivariate analysis (p = 0.01; hazard ratio, 0.22; 95% CI, 0.05-0.73). The most common sites of metastasis were the lungs (30/49, 61%) followed by the pleura (24/49, 49%) and then the liver (20/49, 41%), bones (20/49, 41%), and peritoneum (20/49, 41%). A significantly higher proportion of patients with extrathoracic SFT had metastatic disease (37/139, 27%) compared with those with thoracic SFT (12/139, 9%) (p = 0.003). The overall metastasis-free survival was a median of 117 months (IQR, 33-169 months) in patients with extrathoracic SFT and a median of 120 months (IQR, 82-169 months) in patients with thoracic SFT (p = 0.01). A mitotic count of ≥ 4 per 10 HPF or malignant pathology was significantly associated with metastatic disease on both univariate and multivariate analyses. The sites of metastatic disease differed depending on the site of the primary SFT but were most commonly the lung and pleura. Patients with extrathoracic SFT were statistically more likely to develop metastatic disease than those with thoracic SFT.

NAB2-STAT6 gene fusion and STAT6 immunoexpression in extrathoracic solitary fibrous tumors: the association between fusion variants and locations.

Solitary fibrous tumor (SFT) is a rare mesenchymal neoplasm harboring NAB2-STAT6 fusion, which drives STAT6 nuclear relocation. For extrathoracic SFTs, the clinical relevance of this molecular hallmark remains obscure. We assessed STAT6 immunoexpression for 61 extrathoracic SFTs exclusive of the meninges and head and neck, and 25 had analyzable RNAs to distinguish fusion variants by RT-PCR. The immunohistochemical and molecular findings were correlated with clincopathological features and disease-free survival (DFS). Twenty-eight males and 33 females had SFTs in the body cavities (n=31), extremities (n=17), and trunk (n=13), categorized into 53 non-malignant and 8 malignant tumors. The vast majority (n=57, 93%) exhibited distinctive STAT6 nuclear expression, including malignant ones. The common fusion variants were NAB2ex6-STAT6ex16/17 in 13 SFTs and NAB2ex4-STAT6ex2 in 8, while miscellaneous variants were detected only in 4 SFTs in the limbs and trunk but not in any body cavity-based cases (P=0.026). The worse DFS was univariately associated with malignant histology (P=0.04) but unrelated to tumor size, location, or fusion variant. Conclusively, extrathoracic SFTs mostly harbor NAB2ex6-STAT6ex16/17, followed by NAB2ex4-STAT6ex2. Miscellaneous variants are significantly rare in SFTs within the body cavities. The clinical aggressiveness of extrathoraic SFTs is associated with malignant histology but unrelated to the NAB2-STAT6 fusion variants.

A Case of Wandering Malignant Solitary Fibrous Tumor

Introduction: Solitary fibrous tumor (SFT) is a rare mesenchymal tumor of fibroblastic origin, which may originate from any part of body but most commonly arises from the visceral pleura. We present a rare case of wandering malignant SFT, arising from the lesser omentum. Case: A 60 year old Caucasian male with history of hypertension and diabetes mellitus, admitted initially, for fall in nursing home, developed nausea, vomiting and abdominal distension. A palpable mass was noted on abdominal examination. Non-contrast CT revealed a 17 cm pedunculated bilobed mass with eccentric calcifications in right mid abdomen compressing pylorus with a markedly distended stomach and gastric wall pneumatosis. Repeat CT abdomen with contrast in 12 hours showed interval migration of the mass into the left abdomen with twisting of the mesenteric root and narrowing of the venous structures. The patient underwent emergent exploratory laparotomy with resection of a 1.5 kg mass. Biopsy revealed spindle cell proliferation and abundant collagenous stroma along with large necrotic areas and increased mitotic activity. Immunohistochemical stains were positive for CD34 and STAT6 consistent with malignant SFT. Patient had an uneventful postoperative course and repeat CT imaging after 3 months confirmed complete resolution. Discussion: SFTs are mesenchymal tumors commonly arising from pleura but extrathoracic SFTs have been reported such as intra-abdominal originating from omentum as in our case. Majority of SFTs are benign while 12-22% are malignant. Mean age of onset is 55-65 years. These may be associated with paraneoplastic syndromes, most commonly hypoglycemia or hypertrophic pulmonary osteoarthropathy. Differential diagnoses include gastrointestinal stromal tumor, neurogenic tumors, myogenic tumors or vascular tumors. CD 34 and STAT6 are useful positive biomarkers for SFT as in our case. Molecular hallmark in SFT is recurrent gene fusion of NAB2-STAT6 on chromosome 12q13-15. Imaging modalities including CT or MRI can be suggestive of the diagnosis but definitive diagnosis requires a tissue specimen. The mainstay of treatment is complete surgical resection with clear margins. They can have unpredictable biological behavior and can recur locally or disseminate. Long-term surveillance is recommended post operatively, as disseminated recurrence can occur in tumors with histological features of malignancy, but data to guide further management of such patients is lacking.Figure 1Figure 2

Clinicopathological findings in a case series of abdominopelvic solitary fibrous tumors.

Solitary fibrous tumors (SFTs) represent a rare type of soft tissue tumor. Extrathoracic SFTs (ESFTs) in the soft tissues of the abdominopelvic cavity are extremely rare. Between January 2002 and January 2013, 10 patients were identified with abdominopelvic SFTs at the Northern Jiangsu People’s Hospital. The clinicopathological data, treatment and follow-up results were retrospectively analyzed in this study. Patients included four females and six males, whose age ranged between 21 and 75 years (mean, 53.3 years). The maximum diameter of the tumors was 2.5–28 cm (mean, 12.7 cm). Two cases were diagnosed as malignant variants of ESFTs. R0 resection was performed in eight patients, while one patient underwent R1 resection, and one patient received palliative chemotherapy for an inoperable mass. Follow-up time ranged between 6 and 126 months (mean, 50 months). The patient with R1 resection suffered a local relapse, and the patient receiving palliative chemotherapy succumbed to the disease. The remaining eight patients remained free of disease. Abdominopelvic SFTs usually reveal an indolent process, although the majority of tumors in the present study were of giant size when diagnosed. The risk of local recurrence and metastasis correlates with tumor size and the histological status of surgical margins. The preferred treatment is complete resection followed by extended follow-up surveillance.

Predicting Behavior of Solitary Fibrous Tumor: Are We Getting Closer to More Accurate Risk Assessment?

Predicting clinical behavior of solitary fibrous tumor (SFT) has long been a notoriously difficult task for both oncologist and surgical pathologist. It is well established that morphologically benign tumors may occasionally metastasize and conversely that many tumors, *45 %, classified as malignant based on histologic findings have an indolent clinical course. In this regard, SFT represents a biologic continuum with regard to both histologic appearances and clinical behavior. Although many studies have examined clinical and pathological parameters that may predict risk of relapse in SFT, the majority of these studies have examined small case numbers with limited follow-up. In this issue of Annals of Surgical Oncology, two separate groups have attempted to define clinical and pathologic factors that may predict local recurrence and distant metastasis, by retrospective analysis of 83 and 81 patients with SFT, at a wide variety of anatomic sites, respectively. In both studies, the presence or absence of certain histologic features was gleaned from review of pathology reports. Wilky and colleagues found that anatomic site, specifically extrathoracic location, and the presence of histologic features said to be diagnostic of malignancy as described by England in 1989 (hypercellularity, [4 mitoses per 10 high-power fields [HPF], pleomorphism), as well as ‘‘atypical’’ histologic features that were considered ‘‘borderline’’ by Wilky et al. (0–4 mitoses per HPF, foci of hypercellularity, and atypia) were significantly associated with either local recurrence or distant metastasis. However, the relative impact of each of these histologic features was not evaluated by multivariate analysis. They reported overall rates of 12 and 5 % for local recurrence and metastasis, respectively, with a median follow-up time of 37 months. As might be expected (because of inevitably narrow or positive excision margins), the highest rate of local recurrence occurred in SFT of the CNS, which (in this study) represented 29 % of the study population, but the association between extrathoracic location and increased recurrence rate persisted when CNS tumors were excluded. Although, in this study extrathoracic SFT was more likely to have atypical or malignant histologic features, the difference in recurrence rate (local or distant) seen in extrathoracic locations persisted after correction for size, histologic features, and margin status. Tumor size was not significantly associated with local recurrence or metastasis, but size [10 cm was associated with malignant histology. Van Houdt et al. found that tumor size [10 cm and mitoses [4 per 10 high-power fields predicted metastasis in a cohort of 81 patients. The rates of local recurrence (29 %) and metastasis (34 %), with a median follow-up of 34 months, were substantially higher than those in the cohort studied by Wilky et al., perhaps reflecting referral bias to the tertiary centers involved in the Dutch study, as the follow-up periods were similar in duration in both studies. Local recurrence was significantly associated with positive resection margins at the time of initial surgery, reflecting the unusually high proportion of head and neck tumors in this series, accounting for 27 % of cases. In contrast to Wilky and colleagues, these authors did not find a significant correlation between anatomic location and the development of recurrent disease. With regard to anatomic site, most previous studies have not shown a significant correlation between anatomic site and the development of metastasis, although studies have been limited by small sample size and short follow-up. Approximately 10 % of extrathoracic SFTs showed local recurrence or metastasis in a study by Vallat-Decouvelaere Society of Surgical Oncology 2013

Extrathoracic Location and “Borderline” Histology are Associated with Recurrence of Solitary Fibrous Tumors After Surgical Resection

Most solitary fibrous tumors (SFTs) are cured by complete resection, but many recurrent and metastatic SFTs do not respond to treatment and are fatal. Malignant histology, defined by England's pathologic criteria, is strongly associated with recurrence, but some benign SFTs still behave aggressively. Several studies have suggested that extrathoracic SFTs have a worse prognosis. We reviewed thoracic and extrathoracic SFTs from our institution to determine if extrathoracic location is associated with recurrence, independent of malignant histology. With IRB approval, we retrieved patient pathology reports from the Johns Hopkins Surgical Pathology database between 1991 and 2011 and included 83 SFT patients in our analysis. Patient history and outcomes were obtained from the medical record and primary care physicians. Predictors of recurrence were analyzed by univariate and multivariate analysis and survival determined by the Kaplan-Meier method. Of the 83 patients, 59 had extrathoracic SFTs in neurologic (n = 24), extremity or head/neck (n = 13), or visceral/intraabdominal (n = 22) sites. A total of 74 SFTs were classified benign and 9 as malignant. Of the 14 recurrences, 13 occurred in extrathoracic SFTs; only 7 were classified as malignant. Multivariate analysis confirmed that malignant histology had the strongest association with recurrence, but extrathoracic location also independently predicted recurrence. A total of 20 benign SFTs possessed 1 or more of England's criteria but to an insufficient degree for malignant classification. These "borderline" SFTs were more likely to recur than benign SFTs without these features. Extrathoracic and "borderline" SFTs with any of England's criteria have a higher risk of recurrence.

Solitary fibrous tumor arising slowly in the vulva over 10 years: Case report and review

Solitary fibrous tumor (SFT), which was first described as a pleural lesion by Klemperer and Rabin in 1931, is a rare, slow-growing neoplasm characterized by the proliferation of fibroblast-like spindle cells arranged in a patternless manner with few nuclear atypia. Extrathoracic SFT have increasingly been recognized, but those in the genital tract are extremely rare. Gynecological SFT behave as tumors with low malignant potential to recur, metastasize, or affect nearby organs resulting in infertility. We report a case of vulvar SFT slowly growing for 10 years, and propose a strategy for the diagnosis and treatment of gynecological SFT.

F-18 FDG PET/CT and Tc-99m Sulfur Colloid SPECT imaging in the diagnosis and treatment of a case of dual solitary fibrous tumors of the retroperitoneum and pancreas

Although FDG PET is increasingly used for the staging of many types of sarcoma, little has been written regarding the FDG PET imaging characteristics of solitary fibrous tumor. We report a patient undergoing FDG PET/CT surveillance for squamous cell carcinoma of the tongue who was incidentally found to have two soft tissue masses in the retroperitoneum and pancreatic tail. Due to their low degree of FDG avidity, they were followed conservatively for approximately one year as they gradually increased in size. Technetium-99m sulfur colloid SPECT helped confirm that the pancreatic tail mass was not a splenule, after which both lesions were surgically resected and found to be extrathoracic solitary fibrous tumors without malignant features. These findings suggest that, as with other low-grade sarcomas, benign extrathoracic solitary fibrous tumors exhibit relatively little glycolytic metabolism in vivo.

Giant solitary fibrous tumor arising from greater omentum

Extrathoracic solitary fibrous tumors (SFTs) have been described at almost every anatomic location of human body, but reports of SFT in the abdominal cavity are rare. We herein present a rare case of SFT originating from greater omentum. Computed tomography revealed a 15.8 cm × 21.0 cm solid mass located at superior aspect of stomach. Open laparotomy confirmed its mesenchymal origin. Microscopically, its tissue was composed of non-organized and spindle-shaped cells exhibiting atypical nuclei, which were divided up by branching vessel and collagen bundles. Immunohistochemical staining showed that this tumor was negative for CD117, CD99, CD68, cytokeratin, calretinin, desmin, epithelial membrane antigen, F8 and S-100, but positive for CD34, bcl-2, α-smooth muscle actin and vimentin. The patient presented no evidence of recurrence during follow-up. SFT arising from abdominal cavity can be diagnosed by histological findings and immunohistochemical markers, especially for CD34 and bcl-2 positive cases.

Solitary fibrous tumor of the mediastinum

An 18-year-old man was referred to our hospital for further evaluation of a right anterior mediastinal tumor that measured 6 cm in diameter. Computed tomography-guided transcutaneous aspiration biopsy was performed, but no definitive diagnosis could be obtained. Because the tumor did not appear to be a high-grade malignant tumor, we undertook resection of the tumor to obtain a definitive diagnosis and provide appropriate treatment. Total thymectomy with tumor resection was performed through a median sternotomy. The tumor was solid, measuring 5.2 x 4.2 x 3.5 cm. The histological diagnosis was solitary fibrous tumor (SFT) arising from the mediastinum. Most extrathoracic SFTs appear to pursue a benign course, although careful long-term follow-up of these patients is necessary because the tumors have been reported to recur or metastasize in some cases.

Expanding the Spectrum of Malignant Progression in Solitary Fibrous Tumors

Dedifferentiation is a well recognized, if sometimes controversial, form of tumor progression in certain types of soft tissue and bone sarcoma, and confers a worse prognosis when compared with the low-grade counterpart. To date, dedifferentiation has not been described in solitary fibrous tumor (SFT). Among 948 cases of both intrathoracic and extrathoracic SFTs in our files accessioned between 1988 and 2008, we identified 8 cases of conventional SFT with a discrete anaplastic component, which we believe represents dedifferentiation. These occurred in 3 men and 5 women, 40 to 76 years old (median 60 y), and measured 3.4 to 20.0 cm (median 8.5 cm). Two cases were intrathoracic, 2 were located in the deep soft tissue of thigh, and single cases were located in the omentum, scalp, retroperitoneum, and abdominal wall. In addition to typical features of benign-appearing SFT there was an abrupt transition to nondistinctive high-grade sarcoma in all cases. The latter included epithelioid, round cell, and/or spindle cell components with increased mitotic activity, necrosis, and cystic degeneration. By immunohistochemistry, 7 of 8 cases were CD34 positive in the usual SFT areas, whereas 5 showed loss of CD34 in the poorly differentiated component. Six of 7 cases stained for p53 and p16 showed either negative or scattered positive cells in well-differentiated SFT areas, in contrast to positive or stronger and more diffuse staining in the high-grade component. Follow-up information available in 7 patients ranged from 1 to 58 months (mean 24 mo). Three patients with the largest tumors (9.0, 17.0, and 20.0 cm) died of disease, whereas 3 patients whose tumors measured 8.0 cm or less were treated by surgical excision only, and show no evidence of disease but with only limited follow-up. One patient with an 11.5 cm intrathoracic tumor is alive with disease at 58 months after recurrence and metastasis. We describe, apparently for the first time, what seems, at least in our view, to be dedifferentiation in primary SFT. Our results demonstrate that dedifferentiation in SFT, comparable with that in other low grade/intermediate soft-tissue tumors, poses a higher risk of tumor recurrence and/or metastasis, most notably in large and deep-seated tumors. Similar to other dedifferentiated sarcomas, abrupt transition between low grade and high-grade areas is typically observed with loss of CD34 positivity. The p53 and p16 overexpression in the high-grade component is common as in other dedifferentiated lesions, perhaps pertaining to the underlying molecular mechanism.

Solitary fibrous tumors of the pelvis: Report of two cases with radio-pathological correlation

Solitary fibrous tumors (SFT) are rare neoplasm usually arising from the pleura. The literature contains few reports on the radiologic findings of extrathoracic SFT. We present two cases of SFT of the pelvis and emphasize the diagnostic value of MRI and pathoanatomic features and necessity of long-term follow-up.

Giant Pelvic Solitary Fibrous Tumor Obstructing Intestinal and Urinary Tract: A Case Report and Literature Review

We are reporting a giant pelvic neoplasm, a rare solitary fibrous tumor that presented with a large bowel obstruction and bilateral ureteral obstruction because of its size and location. Preoperative diagnosis required complex pathological studies to exclude a high-grade sarcoma suspected clinically. Complete resection was required for resolution of obstructive symptoms. Prognosis for solitary fibrous tumors is usually good after complete resection. Recurrence and metastasis may be related to rare aggressive histological features, including nuclear atypia, hypercellularity, greater than four mitoses/10 high power fields, and necrosis. Because histology is not always a reliable predictor of prognosis, careful long-term follow-up is necessary for this tumor. Solitary fibrous tumors (SFTs) are rare spindle cell neoplasms most likely arising from mesenchymal cells. SFTs were originally described in the pleura, the most common site for this tumor; however, extrathoracic SFTs are seemingly diagnosed with increased frequency. We report a case of a giant pelvic SFT that required complicated clinical management.

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

BackgroundSolitary 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.MethodsData 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.ResultsThere 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.ConclusionESFT 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.

Extrathoracic solitary fibrous tumor of the pelvic peritoneum with central malignant degeneration on CT and MRI

We describe a 61-year-old man who presented with an extrathoracic solitary fibrous tumor (SFT) of the pelvic peritoneum with central malignant degeneration as seen on computed tomography (CT), magnetic resonance imaging (MRI), and histopathology. When a central focus of heterogeneity and variable contrast enhancement are identified within a fibrous tumor of the pelvis on CT or MRI, malignant degeneration of an extrathoracic SFT, although rare, should be considered as a diagnostic possibility.

Solitary fibrous tumor of the kidney originating from the renal capsule and fed by the renal capsular artery

Solitary fibrous tumors (SFT) are relatively rare spindle cell neoplasms that typically arise in the pleura. Recently, extrathoracic SFT that have arisen in various anatomic sites have been recognized. The histogenesis and prognosis of SFT of the kidney are not well understood because only 11 cases have been reported. We report a case of SFT of the left kidney arising from the renal capsule. The tumor was merged with the upper pole of the left renal capsule. The angiography revealed that the renal capsule artery fed the tumor. The tumor was a well-circumscribed, solid mass attached to the renal capsule without necrosis or hemorrhage. Microscopically the bland spindle cells proliferated and were accompanied by hyalinized collagenous tissue showing patternless or hemangiopericytomatous patterns. Some glomeluri and renal tubules were entrapped by the tumor cells. There were no mitotic figures. Immunohistochemically the tumor cells were diffusely positive for CD34, CD99 and bcl-2. There was no evidence of recurrence after a 4 year follow-up visit. The origin of SFT of the kidney remains uncertain. The tumor in this case merged with the renal capsule and was fed by the renal capsular artery, which suggests that some SFT of the kidney originate from the renal capsule.

Clinicopathologic correlates of solitary fibrous tumors

Solitary fibrous tumors (SFTs) are rare fibrous neoplasms. Since their initial description as arising from the pleura, SFTs have been reported at a wide range of anatomic sites. To the authors's knowledge, there are no large series reporting both thoracic and extrathoracic SFTs nor are there any large series that analyze clinicopathologic correlates of tumor behavior. Institutional soft tissue tumor and pathology databases were reviewed to identify patients. Pathologic material was reviewed by an experienced soft tissue pathologist and scored for the presence of a histologically malignant component. Clinical information was obtained from medical records and phone calls to patients. Statistical analysis was performed using the Student t test, Pearson chi-square test, and log-rank test. Seventy-nine patients with SFTs treated at a single institution over an 18-year period were identified. These tumors arose in a wide range of anatomic sites. Thoracic and extrathoracic SFTs had similar clinical and pathologic features, although extrathoracic tumors were more likely to be symptomatic on diagnosis. Seventy-five patients underwent surgical excision of a SFT at our institution. Overall, SFTs had a low rate of local recurrence and metastasis after surgical treatment. Extrathoracic SFTs had an increased risk of local recurrence that was small but statistically significant. There was no difference in metastasis-free survival between thoracic and extrathoracic SFTs. Positive surgical margins and the presence of a histologically malignant component were factors predicting worse local recurrence-free survival. Positive surgical margins, tumor size greater than 10 cm, and the presence of a malignant component predicted worse metastasis-free survival. Solitary fibrous tumors are rare tumors that occur at all anatomic sites. Most SFT patients fare well after surgical treatment. Closer surveillance is warranted for those tumors that are larger than 10 cm or with the presence of a histologically malignant component.

Extrathoracic solitary fibrous tumors are potentially aggressive

Extrathoracic solitary fibrous tumors are potentially aggressive

Extrathoracic solitary fibrous tumors: Their histological variability and potentially aggressive behavior

The histological variability of solitary fibrous tumors may contribute to the difficulty in diagnosing these neoplasms, especially when they arise in extrathoracic sites. Like intrathoracic lesions, the behavior of extrathoracic solitary fibrous tumors is currently unpredictable because these types of tumor have only recently been recognized. This study therefore was undertaken to examine the clinical behavior and histological, immunohistochemical, and ultrastructural features of 24 extrathoracic solitary fibrous minors with long-term follow-up. The patients comprised 10 men and 14 women, between 30 and 85 years of age (mean, 51 years). Ten tumors were located in the retroperituneum or pelvis, 5 in the trunk, 4 in the extremities, 2 in the orbital region, and 1 each in the kidney, uterine cervix, and meninges. All of the tumors showed a classic morphological appearance, diffuse and strong immunoreactivity for both vimenfin and GD34, and variable reactivity for bcl-2. All 7 cases examined ultrastructurally contained fibroblasts and myolibroblasts. Six tumors contained mulfinucleated giant cells, and in 4 cases these lined pseudovascnlar spaces with mononuclear cells, thus resembling giant cell angiofibroma and giant cell fibroblastoma. Other potentially similar spindle cell neoplasms mixed with adipose tissue, such as dendritic fibromyxolipoma, lipomatous hemangiopericytoma, cellular angiofibroma, and spindle cell lipoma, were considered in the differential diagnosis. One tumor displayed atypical histological features in the form of increased cellularity and nuclear pleomorprism, but this patient has remained free of disease for 14 years. Another 2 patients developed local recurrences at 6 months and 5 years, and a further patient developed pulmonary metastases that were diagnosed after 7 years. These tumors lacked any atypical histological features in the primary lesions. No patient has so far died of the disease. In conclusion, most extrathoracic solitary fibrous tumors appear to pursue a benign course, although, because some have the potential to recur or metastasize, careful long-term follow-up is necessary for all patients.