Ultrastructural observations on the histogenesis of localized fibrous tumours of the pleura (benign mesothelioma)

Giant solitary fibrous tumour of the pleura an unpredictable entity: case series and literature review

A small proportion of tumours can undergo malignant transformation. We report a case series of five patients diagnosed with giant solitary fibrous tumours of the pleura. These cases highlight the unpredictable nature of this disease process, with significant variability in clinical course observed, from indolence to aggressive progression. Three patients were found to have malignant disease on explant, with two of these having preoperative imaging and histology suggesting benign pathology. This finding emphasises that accurately differentiating between benign and malignant disease on imaging and/or biopsy has low specificity and sensitivity and cannot be relied upon in guiding the management of these tumours. Patients with solitary fibrous tumours of the pleura should be managed cautiously, owing to the unpredictable and potentially aggressive clinical course. We would advocate the position that all patients with solitary fibrous tumours of the pleura should be managed as if they have malignant disease. Prolonged follow-up is required due to the risk of disease recurrence, even in patients with benign disease.

The Current Status of Solitary Fibrous Tumor: Diagnostic Features, Variants, and Genetics

Solitary fibrous tumor (SFT) is a fibroblastic mesenchymal tumor originally described in the pleura but now shown at almost every anatomic site. Histopathologically, SFT is characteristically a circumscribed neoplasm composed of variably cellular and patternless distributions of bland spindle and ovoid cells within prominent collagenous stroma and shows diffuse expression of CD34, but it has a broad spectrum of both morphology and of biologic behavior. Many different names (particularly hemangiopericytoma) were previously used in the course of our understanding of this neoplasm but are now subsumed under the term "SFT," and the putative cell of origin was debated. However, it is now recognized that SFT is a translocation-associated neoplasm, consistently associated with NAB2-STAT6 gene fusions arising from recurrent intrachromosomal rearrangements on chromosome 12q, and this translocation is a likely major contributor to its pathogenesis. While most SFT with classical morphologic features behave in an indolent manner and those with overtly malignant histologic features tend to be aggressive neoplasms that behave as high-grade sarcomas, the behavior of SFT is unpredictable, and it is important to be aware of the propensity for aggressive behavior in a minority of histologically classical SFT and to ensure adequate clinical follow-up. Surgical excision remains the treatment gold standard; while radiotherapy and conventional chemotherapeutic agents have only shown limited efficacy, further understanding of the molecular events underlying tumorigenesis may allow the development of novel targeted treatments. We review SFT, discussing the morphologic spectrum and variants, including malignant and dedifferentiated subtypes, clinicopathological aspects, recent molecular genetic findings, and the differential diagnosis.

Gene expression profiling of solitary fibrous tumors

Background

Solitary fibrous tumors (SFTs) are rare spindle-cell tumors. Their cell-of-origin and molecular basis are poorly known. They raise several clinical problems. Differential diagnosis may be difficult, prognosis is poorly apprehended by histoclinical features, and no effective therapy exists for advanced stages.

Methods

We profiled 16 SFT samples using whole-genome DNA microarrays and analyzed their expression profiles with publicly available profiles of 36 additional SFTs and 212 soft tissue sarcomas (STSs). Immunohistochemistry was applied to validate the expression of some discriminating genes.

Results

SFTs displayed whole-genome expression profiles more homogeneous and different from STSs, but closer to genetically-simple than genetically-complex STSs. The SFTs/STSs comparison identified a high percentage (∼30%) of genes as differentially expressed, most of them without any DNA copy number alteration. One of the genes most overexpressed in SFTs encoded the ALDH1 stem cell marker. Several upregulated genes and associated ontologies were also related to progenitor/stem cells. SFTs also overexpressed genes encoding therapeutic targets such as kinases (EGFR, ERBB2, FGFR1, JAK2), histone deacetylases, or retinoic acid receptors. Their overexpression was found in all SFTs, regardless the anatomical location. Finally, we identified a 31-gene signature associated with the mitotic count, containing many genes related to cell cycle/mitosis, including AURKA.

Conclusion

We established a robust repertoire of genes differentially expressed in SFTs. Certain overexpressed genes could provide new diagnostic (ALDH1A1), prognostic (AURKA) and/or therapeutic targets.

[Solitary fibrous tumour of the pleura: about five cases]

BACKGROUND

Pleural solitary fibrous tumour (PSFT) is a rare, usually benign tumour, with unpredictable behaviour.

PATIENTS AND METHODS

Five cases of PSFT were diagnosed in our department over a 12-year period from January 1999 to December 2010. Clinical, radiological, histological, therapeutic and follow-up information were provided in all cases.

RESULTS

Our series comprised four men and one woman. The mean age of the patients at presentation was 55 years. All patients were symptomatic. Radiologic investigations showed a pleural lesion with a mean size of 10.6cm ranging from 3 to 17cm. Histologic diagnosis was made from resected parietal pleura in three cases and visceral pleura in two cases. The histologic features were suggestive of malignancy in two cases and benign in three cases. Immunohistochemical study showed that the tumour cells expressed vimentin, CD34, CD99 and Bcl2. Complete resection was obtained in all patients. The evolution was marked in the two patients with malignant PSFT by the recurrence of the tumour after 6 and 21 months respectively. Both died from the condition. The three patients with a benign form are disease-free after 3, 11 and 2 and half years of follow-up.

CONCLUSIONS

PSFT is rare tumour, the diagnosis of which is based on histologic investigations. These tumours require long-term monitoring due to the possibility of local recurrence and malignant transformation.

Recurrent solitary fibrous tumor of the pleura with malignant transformation and non-islet cell tumor-induced hypoglycemia due to paraneoplastic overexpression and secretion of high-molecular-weight insulin-like growth factor II

A 41-year-old man was diagnosed with a solitary fibrous tumor (SFT) of the pleura in the posterior mediastinum. Despite two surgeries for excision, the SFT recurred and progressed with direct invasion of the chest wall and bone metastases. He was hospitalized because of cerebral infarction and presented with recurrent severe hypoglycemia fourteen years later. High-molecular-weight (HMW) insulin-like growth factor II (IGF-II) was identified in the serum and tumor using Western blotting and immunohistochemistry. These findings suggested that the cause of the recurrent severe hypoglycemia was SFT production of HMW IGF-II, a mediator of non-islet cell tumor-induced hypoglycemia (NICTH).

Hyper-IgG4 disease: report and characterisation of a new disease

BACKGROUND

We highlight a chronic inflammatory disease we call 'hyper-IgG4 disease', which has many synonyms depending on the organ involved, the country of origin and the year of the report. It is characterized histologically by a lymphoplasmacytic inflammation with IgG4-positive cells and exuberant fibrosis, which leaves dense fibrosis on resolution. A typical example is idiopathic retroperitoneal fibrosis, but the initial report in 2001 was of sclerosing pancreatitis.

METHODS

We report an index case with fever and severe systemic disease. We have also reviewed the histology of 11 further patients with idiopathic retroperitoneal fibrosis for evidence of IgG4-expressing plasma cells, and examined a wide range of other inflammatory conditions and fibrotic diseases as organ-specific controls. We have reviewed the published literature for disease associations with idiopathic, systemic fibrosing conditions and the synonyms: pseudotumour, myofibroblastic tumour, plasma cell granuloma, systemic fibrosis, xanthofibrogranulomatosis, and multifocal fibrosclerosis.

RESULTS

Histology from all 12 patients showed, to varying degrees, fibrosis, intense inflammatory cell infiltration with lymphocytes, plasma cells, scattered neutrophils, and sometimes eosinophilic aggregates, with venulitis and obliterative arteritis. The majority of lymphocytes were T cells that expressed CD8 and CD4, with scattered B-cell-rich small lymphoid follicles. In all cases, there was a significant increase in IgG4-positive plasma cells compared with controls. In two cases, biopsies before and after steroid treatment were available, and only scattered plasma cells were seen after treatment, none of them expressing IgG4. Review of the literature shows that although pathology commonly appears confined to one organ, patients can have systemic symptoms and fever. In the active period, there is an acute phase response with a high serum concentration of IgG, and during this phase, there is a rapid clinical response to glucocorticoid steroid treatment.

CONCLUSION

We believe that hyper-IgG4 disease is an important condition to recognise, as the diagnosis can be readily verified and the outcome with treatment is very good.

Solitary fibrous tumor of the thyroid with capsular invasion

This report describes the clinical and pathologic findings of a peculiar case of solitary fibrous tumor of the thyroid gland that showed capsular invasion. After four and a half years of follow-up, neither local recurrence nor metastasis has developed.

Solitary fibrous tumor of nasal cavity in patient with long-standing history of cocaine inhalation

We report a solitary fibrous tumor in the nasal cavity of a 48-year-old woman who presented with a history of bilateral nasal obstruction and long-standing cocaine inhalation. Physical examination revealed a large mass involving the right nasal cavity and extending into the posterior aspect of the left nasal cavity. The computed tomography scan showed opacification of airways. During surgery, the mass was found to involve the entire nasal cavity, with extension to the right maxillary sinus, posterior nasal airways, and left nasal cavity. The mass was completely excised. Pathologic examination revealed a polypoid mass 3.7 x 3.0 x 1.2 cm. This tumor was composed of spindle cells that were cytologically bland in a background of ropey and nodular collagen, giving a "patternless" pattern. Immunohistochemically, the neoplastic cells stained for CD34 and vimentin but not for S100 protein, keratin, desmin, HMB-45, and c-Kit. This immunohistochemical pattern confirmed the diagnosis of solitary fibrous tumor. Although solitary fibrous tumors are usually found in the pleura, they can occur in various other locations, such as the orbit, nasal cavity, paranasal sinuses, mediastinum, breast, vagina, meninges, and soft tissues. This case is of interest because the tumor occurred in a patient with prolonged cocaine inhalation. Such an association has not been previously described. The exact causal relationship between cocaine inhalation and the tumor is not known.

Intramuscular solitary fibrous tumor: a clinicopathological case study

We present a case of extrapleural solitary fibrous tumor arising within the muscle, an unusual and hitherto-undescribed tumor lesion. A 42-year-old woman presented a painless mass in her left thigh. The lesion was depicted as an intramuscular mass that enhanced on both CT and MRI, showing quite rich tumor vascularity. The histological features of the tumor were spindle cell proliferation with various histological patterns, typical fibrocollagenous background, and positive immunoreactivity for CD-34.

Solitary fibrous tumor of the liver: a clinicopathologic and immunohistochemical study of nine cases

Nine cases of primary solitary fibrous tumors of the liver are presented. The patients are 7 women and 2 men between the ages of 32 and 83 years (mean, 57.5 years). Clinically, palpable masses were detected during physical examination in five patients. Two patients presented with symptoms of cholecystitis, one with hematuria, one with periumbilical pain, and one with hypoglycemia. One patient was found to have an abdominal mass during follow-up evaluation for colonic carcinoma, whereas in one patient the tumor was an incidental finding at autopsy. Two patients were asymptomatic, and the tumor masses were detected during a routine physical examination. Grossly, the tumors varied in size from 2 to more than 20 cm in greatest dimension and were described as firm, white-to-gray, well or ill defined. Eight tumors were described as intraparenchymal lesions, two were grossly necrotic, and one tumor was attached by a pedicle to the liver capsule without infiltration into the liver parenchyma. Histologically, most of the tumors had a bland appearance with the classic short storiform (so-called patternless) pattern and absence of cellular atypia, mitoses and/or necrosis. However, in two cases, there was marked cellular atypia and mitotic figures varying from 2 to 4 mitoses per 10 high power field (hpf). Immunohistochemically, all the tumors showed a strong positive reaction against antibodies for CD-34 and vimentin. Follow-up information showed that two patients died within days of postsurgical resection of the tumor, whereas one was alive and well 1 year after initial diagnosis. No follow-up information was available for the other five patients. The cases herein presented highlight the ubiquitous distribution of this neoplasm and the similar clinical and histopathological features to those observed in serosal surfaces. Solitary fibrous tumors of the liver, although rare, need to be considered in the differential diagnosis of mesenchymal lesions of the liver.

Solitary fibrous tumor of the spinal cord

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

Malignant solitary fibrous tumor of the pleura

We describe a case of malignant solitary fibrous tumor of the pleura in a 15-year-old female who presented clinically with back pain. Grossly, the tumor had a pedicle attached to the pleura and histologically showed proliferating spindle-shaped cells with a high mitotic index. Immunohistochemical and ultrastructural features were consistent with a tumor of fibroblastic origin. Flow cytometric DNA analysis revealed an aneuploid population among the tumor cells.

Solitary fibrous tumor of the pleura. An immunohistochemical, electron microscopic and tissue culture study of a tumor producing insulin-like growth factor I in a patient with hypoglycemia

We report a patient with recurrent hypoglycemia most likely caused by a solitary fibrous tumor of the pleura. After removal of the tumor, hypoglycemia resolved. The bland histologic picture of this tumor is emphasized. Electron microscopic and immunohistochemical observations support its non-mesothelial derivation. In vitro studies demonstrated that the tumor tissue produced insulin-like growth factor I (IGF-I), and its role as the cause of hypoglycemia is discussed.

Localized fibrous tumor (localized fibrous mesothelioma) of the liver

A case of localized fibrous tumor (LFT) (localized fibrous mesothelioma) of the liver in an 83-year-old woman is presented. The tumor was 15 x 9 x 8 cm and was confined to the left lateral segment of the liver. Occasional mitotic figures (MF) (2 to 3 per 50 high-power fields [HPF]) were present. Strong, diffuse vimentin positivity was demonstrated by immunohistochemistry. Immunoreactivity for cytokeratins (AE1-3), epithelial membrane antigen (EMA), desmin, and desmosomal proteins (desmoplakin I + II) was absent. Electron microscopic examination showed a mesenchymal appearance of the majority of neoplastic cells, with a few ultrastructural features suggestive of mesothelial differentiation. These findings supported a submesothelial origin of the tumor. After a partial hepatectomy with total gross and microscopic removal of the tumor, the patient was alive without recurrence at 2 years, 5 months later. A review of the English literature showed six additional cases that are probably similar. Currently, all tumors have been clinically benign, although follow-up information has been limited.

Haemangiopericytoma of the diaphragm

This paper reports the pathological features of a diaphragmatic haemangiopericytoma with a discussion of diagnostic difficulties it may present in relation to other localised mesenchymal tumours of the pleura. The published reports of diaphragmatic haemangiopericytoma in the world english language literature are reviewed.

Solitary fibrous tumour of the pleura: an ultrastructural and immunohistochemical study

Solitary fibrous tumour of the pleura is a benign neoplasm differing from diffuse pleural mesothelioma. It was originally thought to be a variant of mesothelioma because it consists of a spindle cell stroma associated with branching tubular structures lined by cuboidal cells. In this study of two cases the tubular structures were lined with ciliated and non-ciliated cuboidal cells. Ultrastructurally most of the non-ciliated cells had the features of type II pneumocytes, while the stromal cells had all the characteristics of fibroblasts. Immunohistochemical staining showed the epithelial cells to be positive for both keratin and carcinoembryonic antigen, whereas the stromal cells were negative. The findings support the theory that these tumours are fibroblastic in origin, and that the biphasic pattern is due to entrapment of non-neoplastic bronchiolar and alveolar epithelial cells.

Localized fibrous tumour of serosal surfaces. Immunohistochemical and ultrastructural evidence for a type of mesothelioma

It is uncertain whether localized lesions of serosal membranes have a kinship to mesotheliomas or are truly fibromatous in nature. Ultrastructural and immunohistochemical investigations were carried out on 12 localized benign and malignant pleural and peritoneal tumours from 10 patients. Electron microscopic findings, including the consistent and non-fibroblastic cellular organization of localized neoplasms, the presence of some form of intercellular junctions in 7 of 10 cases, basal lamina deposition in 3 cases, and polarized microvilli in one case indicated a form of mesothelial differentiation. Using monoclonal and polyclonal antibodies, positive immunostaining of tumour cells for cytokeratin peptides was detected in one case, while antibody to vimentin stained four cases. Light microscopic, ultrastructural and immunohistochemical features of one benign localized serosal tumour, with a unique blend of epithelial and spindle cells, provided further evidence for a histogenic link between localized serosal tumours and diffuse epithelial mesotheliomas. On the basis of the current findings and reports in the literature, it would appear that the majority of localized tumours of serosal membranes are a subset of mesothelioma, while a minority are fibromas.