Expression of CD34 by solitary fibrous tumors of the pleura, mediastinum, and lung

Solitary Fibrous Tumor of Breast and Axilla: Clinicopathological Profile of Five Tumors With Comparison of Risk Stratification Models

Introduction: Solitary fibrous tumor (SFT) is a fibroblastic tumor with malignant potential that is underpinned by a recurrent inv12(q13q13)-derived NAB2::STAT6 fusion. Breast and axilla are uncommon locations for this entity. Methods: Records of two academic institutions were electronically searched for breast and axillary SFTs. Clinical and pathologic data were reviewed. Literature review for breast or axillary SFTs was performed. Present study and previously reported tumors were stratified using five SFT risk models: original and modified Demicco metastatic risk, Salas local recurrence risk, Salas metastatic risk, and Thompson local recurrence risk. Results: Five patients with breast or axillary SFT were identified. Median age was 49 years, and median follow-up (available for four patients) was 82 months. Three patients showed no evidence of disease, and one developed recurrence. Literature review identified 58 patients with breast or axillary SFT. Median age was 54 years, and median follow-up (available for 35 patients) was 24 months. Thirty-one patients showed no evidence of disease, three developed recurrence, and one developed metastasis. Original and modified Demicco models and Thompson model showed the highest sensitivity; original and modified Demicco models and Salas metastatic risk model demonstrated the highest specificity. Kaplan-Meier models were used to assess recurrence-free probability (RFP). Original and modified Demicco models predicted RFP when stratified by "low risk" and "moderate/intermediate and high risk" tumor, though sample size was small. Conclusions: While many SFTs of breast and axilla remain indolent, a subset may develop recurrence and rarely metastasize. The modified Demicco risk model demonstrated optimal performance characteristics.

STAT6-targeting antisense oligonucleotides against solitary fibrous tumor

Solitary fibrous tumor (SFT) is a rare, non-hereditary soft tissue sarcoma thought to originate from fibroblastic mesenchymal stem cells. The etiology of SFT is thought to be due to an environmental intrachromosomal gene fusion between NGFI-A-binding protein 2 (NAB2) and signal transducer and activator protein 6 (STAT6) genes on chromosome 12, wherein the activation domain of STAT6 is fused with the DNA-binding domain of NAB2 resulting in the oncogenesis of SFT. All NAB2-STAT6 fusion variations discovered in SFTs contain the C-terminal of STAT6 transcript, and thus can serve as target site for antisense oligonucleotides (ASOs)-based therapies. Indeed, our in vitro studies show the STAT6 3' untranslated region (UTR)-targeting ASO (ASO 993523) was able to reduce expression of NAB2-STAT6 fusion transcripts in multiple SFT cell models with high efficiency (half-maximal inhibitory concentration: 116-300 nM). Encouragingly, in vivo treatment of SFT patient-derived xenograft mouse models with ASO 993523 resulted in acceptable tolerability profiles, reduced expression of NAB2-STAT6 fusion transcripts in xenograft tissues (21.9%), and, importantly, reduced tumor growth (32.4% decrease in tumor volume compared with the untreated control). Taken together, our study established ASO 993523 as a potential agent for the treatment of SFTs.

Corneal Infantile Myofibromatosis Caused by Novel Activating Imatinib-Responsive Variants in PDGFRB

Purpose

To investigate the genetic cause, clinical characteristics, and potential therapeutic targets of infantile corneal myofibromatosis.

Design

Case series with genetic and functional in vitro analyses.

Participants

Four individuals from 2 unrelated families with clinical signs of corneal myofibromatosis were investigated.

Methods

Exome-based panel sequencing for platelet-derived growth factor receptor beta gene (PDGFRB) and notch homolog protein 3 gene (NOTCH3) was performed in the respective index patients. One clinically affected member of each family was tested for the pathogenic variant detected in the respective index by Sanger sequencing. Immunohistochemical staining on excised corneal tissue was conducted. Functional analysis of the individual PDGFRB variants was performed in vitro by luciferase reporter assays on transfected porcine aortic endothelial cells using tyrosine kinase inhibitors. Protein expression analysis of mutated PDGFRB was analyzed by Western blot.

Main Outcome Measures

Sequencing data, immunohistochemical stainings, functional analysis of PDGFRB variants, and protein expression analysis.

Results

We identified 2 novel, heterozygous gain-of-function variants in PDGFRB in 4 individuals from 2 unrelated families with corneal myofibromatosis. Immunohistochemistry demonstrated positivity for alpha-smooth muscle actin and β-catenin, a low proliferation rate in Ki-67 (< 5%), marginal positivity for Desmin, and negative staining for Caldesmon and CD34. In all patients, recurrence of disease occurred after corneal surgery. When transfected in cultured cells, the PDGFRB variants conferred a constitutive activity to the receptor in the absence of its ligand and were sensitive to the tyrosine kinase inhibitor imatinib. The variants can both be classified as likely pathogenic regarding the American College of Medical Genetics and Genomics classification criteria.

Conclusions

We describe 4 cases of corneal myofibromatosis caused by novel PDGFRB variants with autosomal dominant transmission. Imatinib sensitivity in vitro suggests perspectives for targeted therapy preventing recurrences in the future.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Mesenchymal tumours of the pleura: review and update

Primary mesenchymal tumours of the pleura are uncommon and can be diagnostically challenging due to their overlapping histopathologic and immunophenotypic features. Herein we discuss selected mesenchymal tumours of the pleura, including solitary fibrous tumour, calcifying fibrous tumour, desmoid fibromatosis, synovial sarcoma, schwannoma, malignant peripheral nerve sheath tumour, inflammatory myofibroblastic tumour, follicular dendritic cell sarcoma, epithelioid hemangioendothelioma, and desmoplastic small round cell tumour. We review their clinicopathologic characteristics, along with an update on the relevant immunohistochemical and molecular features.

Malignant Solitary Fibrous Tumor of the Nasal Cavity and Orbit: A Case Report

Solitary fibrous tumors are well-recognized in the pleura and their occurrence in the nasal cavity is uncommon. They show a hemangiopericytoma-like vasculature, a "patternless pattern" of growth, and lesions characterized by both hypercellularity and hypocellularity. As a malignant form of SFT, mesenchymal neoplasm is extremely uncommon and poorly understood, although there are no established standards for making this diagnosis, it is nonetheless accepted. It can develop either de novo or within an already-existing benign SFT, and there are few published accounts of the cytopathologic characteristics of these tumors.In this case, a patient complained of tenderness on the right nasal root and diplopia for six months. Here, we report on a case of malignant solitary fibrous tumors in the nasal cavity, which extended into the orbit, and review the radiologic and pathologic features.

Solitary Fibrous Tumors of the Female Genital Tract: A Study of 27 Cases Emphasizing Nonvulvar Locations, Variant Histology, and Prognostic Factors

We report 27 solitary fibrous tumors of the female genital tract emphasizing nonvulvar locations, variant histology, and prognostic factors. The patients ranged from 25 to 78 years (most were over 40), and tumors occurred in the vulva (7), vagina (2), cervix (2), corpus (6), fallopian tube/paratubal soft tissue (5), and ovary (5). They ranged from 1.5 to 39 (mean=10.5) cm and were typically solid, but 4 were predominantly cystic. All had a haphazard arrangement of spindled to ovoid cells, with most demonstrating alternating cellular and hypocellular areas and prominent vessels, but 13 lacked hypocellular areas, and 7 had focal diffuse growth with inconspicuous vasculature. Other patterns included corded (8), fascicular (5), trabecular (1), and nested (1). Microcysts (6), myxoid background (8), hyalinization (8), lipomatous differentiation (2), and multinucleated cells (6) were also present, and 10 tumors had necrosis. Vasculature included thin-walled branching "staghorn" (27), thick-walled (7), and hyalinized vessels (5) or dilated anastomosing vascular channels (3). Nuclear atypia ranged from mild (19), moderate (7), to severe (1), and mitoses from 0 to 24/10 HPF (mean=4). STAT6 was positive in all 25 tumors tested. One tumor showed dedifferentiation; the remainder were classified as benign (19) or malignant (7) based on mitotic rate (univariate stratification model) and as low risk (14), intermediate risk (8), or high risk (4) based on the Demicco multivariate risk stratification score. Follow-up (median=23 mo) was available for 16 patients. Six tumors recurred (2 intermediate risk, 3 high risk, and the dedifferentiated tumor), 5 in the abdomen; the dedifferentiated tumor metastasized to the lung. Multivariate risk stratification was superior to univariate classification, as 5 "benign" tumors were reclassified as intermediate risk using the multivariate model; of these, 2 recurred, and 1 patient died of disease. Upper female genital tract tumors occurred in older patients, were larger, and more frequently classified as high risk compared with those of the lower tract. A trend toward increased cellularity was also seen in the upper tract tumors. Only size (P=0.04), necrosis (P=0.04), and Demicco score (P=0.01) independently correlated with recurrence. Female genital tract solitary fibrous tumors demonstrate a wide range of variant morphologies and occur in diverse sites in addition to the vulva. Tumors were often misdiagnosed as other neoplasms; thus, awareness of solitary fibrous tumors occurring at these sites is crucial in prompting staining for STAT6 to establish this diagnosis. The Demicco risk stratification system effectively predicts behavior.

A case of primary orbital solitary fibrous tumor with lung metastases 41 years after initial treatment

Here, we report a case of an orbital solitary fibrous tumor (SFT) with multiple local recurrences, even after orbital exenteration, and lung metastases after 41 years. The report discusses the clinical and histopathological findings of this case. A 34-year-old female patient with an orbital SFT was treated with orbital exenteration after local resection failed to prevent a recurrence. Ten years later, the patient underwent radiation therapy, followed by two rounds of gamma knife treatment, leading to remission. Forty-one years after the first treatment, the patient, at the age of 75 years, was found to have lung metastases along with orbital recurrence for the eighth time. The patient underwent radiation therapy but died from radiation pneumonitis. Our case emphasizes the need for long-term follow-up of patients with orbital tumors, even after orbital exenteration, to monitor for metastasis.

Implications of Adverse Biological Factors and Management of Solitary Fibrous Tumors of the Pleura

Solitary fibrous tumors arise in many locations throughout the body and are genetically and histologically considered a single disease. Solitary fibrous tumors of the pleura (SFTP) are the most common tumor of this disease. Most of the SFTPs are treated with surgery alone, and chemotherapy and radiotherapy do not seem to play a role in treatment. Tumor size and unfavorable histology are risk factors for malignant potential. Incomplete resection is an important risk factor for recurrence.

CD34-negative Solitary Fibrous Tumor: A Clinicopathologic Study of 25 Cases and Comparison With Their CD34-positive Counterparts

CD34-negative solitary fibrous tumors (SFTs) are rare and have not been comprehensively studied. We retrospectively reviewed all cases of SFT confirmed with STAT6 immunohistochemistry and/or STAT6 gene fusion between 2013 and 2020 and collected pertinent clinicopathologic parameters. Of a total of 244 cases, 25 (10%) lacked CD34 expression by immunohistochemistry. Compared with CD34-positive SFT, CD34-negative SFT are more likely to arise in the head and neck area (32% vs. 24%, P=0.02) and present as metastatic disease (28% vs. 1%, P<0.0001). A significantly higher percentage of CD34-negative SFT exhibit high-grade cytologic atypia (hypercellularity, round cell or anaplastic morphology, nuclear pleomorphism, etc.) (48% vs. 22%, P=0.0073). There are no significant differences in the distributions of age, sex, tumor size, mitotic count, tumor necrosis, or risk stratification between CD34-negative and CD34-positive SFT. In addition, only 56% of CD34-negative SFT display a typical hemangiopericytoma-like vascular pattern. Special histologic features among CD34-negative SFT include prominent alternating hypercellular or fibrous and hypocellular myxoid areas with curvilinear vessels mimicking low-grade fibromyxoid sarcoma, pulmonary edema-like microcystic changes, and prominent amianthoid collagen fibers. In conclusion, compared with their CD34-positive counterparts, CD34-negative SFT is more likely to present as metastatic disease, show high-grade nuclear atypia, and lack the characteristic hemangiopericytoma-like vasculature, posing a unique diagnostic challenge. The use of STAT6 immunohistochemistry and/or molecular studies may be prudent in soft tissue tumors that appear CD34 negative and lack conventional SFT histopathologic characteristics.

Solitary fibrous pleural tumor. A rare and challenging case

INTRODUCTION

Solitary fibrous tumor of the pleura (SFTP) is a rare tumor originating from mesenchymal tissue underlying the mesothelial pleural layer with only a limited number of reported cases. Benign and malignant SFTP usually appear as a well-defined, homogeneous, and rounded mass on imaging. Complete en bloc is usually the treatment of choice.

CASE PRESENTATION

44 years old gentleman presented with the unintentional weight loss and chest discomfort for 6 months. A CT scan of chest showed a 30 × 20 × 20 cm heterogeneously enhancing soft tissue mass involving the entire right hemithorax. PET scan showed a localized disease. Therefore, a complete right upper lobectomy and complete removal of mass was done, that resulted in complete expansion of the middle and lower lobe. The patient remains stable till date. Biopsy revealed a fibrous pleural tumor.

CONCLUSION

Complete surgical resection of the tumor is usually sufficient, but there are reported cases with recurrence. Wedge resection for complete excision can be carried out for tumors arising from visceral pleura. Extra pleural excision can be done without chest wall resection in tumors arising from the parietal pleura.

A case of malignant solitary fibrous tumor of the prostatic urethra

A 68-year-old male with dementia presented with gross hematuria. On plain CT, a mass was found at the base of the prostate with intravesical protrusion. On MRI, the mass was well-circumscribed and showed slight hyperintensity compared to the skeletal muscle on T₁ weighted imaging and high intensity on T₂ weighted imaging. On dynamic study, the tumor showed mild enhancement in the early phase and increased enhancement in the delayed phase, and the mass appeared continuous with the prostatic urethra. On follow-up MRI at approximately 10 months, the mass had increased in size. Pathologically, the tumor was located in the muscularis of the prostatic urethra and consisted of spindle cells with fascicular and storiform patterns of growth, and exhibited strong diffuse expression of CD34. The tumor was hypercellular, and a significant number of mitoses were observed. Therefore, this tumor was diagnosed as malignant solitary fibrous tumor (SFT) of the prostatic urethra.

Primary intrapulmonary solitary fibrous tumours

Due to the extreme rarity of primary intrapulmonary solitary fibrous tumours (SFTs), their clinical course, imaging characteristics, diagnosis, treatment and prognosis are poorly understood. The present study therefore assessed the diagnosis and management of primary intrapulmonary SFTs and systematically reviewed previously reported cases in the literature. A total of 5 patients who underwent resection for primary intrapulmonary SFTs were enrolled in the present study and their clinical course, tumour characteristics, management and survival were assessed in this retrospective study. Relevant studies regarding primary intrapulmonary SFTs were searched using PubMed and tumour characteristics, clinicopathologic features, therapeutic strategy and survival outcomes were reviewed. Of the 5 cases, all were males, with a mean age of 57.6 years (range, 37-68 years). All patients were asymptomatic and were identified incidentally on routine computed tomography examination. A total of 3 patients underwent thoracotomy and 2 patients underwent video-assisted thoracoscopic surgery. All tumours were completely resected. Postoperative haemorrhage occurred in 1 patient and he received surgical intervention for haemostasis. The average hospital stay was 15 (4-22) days, and no mortality occurred. The mean length of the postoperative follow-up was 37.6 (1-67) months. One patient was lost to follow-up, and 4 patients were asymptomatic. A total of 19 studies were identified from database searches. They included a total of 45 patients: Twenty-three males and 22 females (mean age, 59.4 years; range, 7-81 years). A total of 12 patients were asymptomatic, and pain and coughing were the major symptoms. Five, one, two, four, and 17 tumours occurred in the right upper lobe, right middle lobe, right lower lobe, left upper lobe and left lower lobe, respectively. A total of 39 patients underwent surgery, 1 patient underwent radiotherapy, and 1 patient underwent radiofrequency ablation. A total of 22 patients were followed up and the mean length of the postoperative follow-up was 48 (1-168) months. One patient was diagnosed with chest wall metastases, and 5 patients succumbed to mortality. To conclude, primary intrapulmonary SFTs are extremely rare and typically identified incidentally. The present findings indicated that the left lower lobe was the most common site location and complete surgical resection is a safe and effective treatment.

Recurrent Severe Hypoinsulinemic Hypoglycemia Responsive to Temozolomide and Bevacizumab in a Patient With Doege-Potter Syndrome

Nonislet cell tumor hypoglycemia is rare. We highlight the diagnosis and treatment of recurrent severe hypoglycemia in a 49-year-old woman with malignant solitary fibrous tumor of the pleura (Doege-Potter syndrome). The clinical, laboratory and radiologic findings of the case are presented and a brief literature review is provided. Of note, imaging studies showed a large mass in the right hemithorax and pathology and immunehistochemical stains confirmed a malignant solitary fibrous tumor of the pleura. She was a poor surgical candidate owing to a large tumor burden. She was treated with a combination of temozolomide and bevacizumab to which she responded with resolution of hypoglycemia. The treatment of choice for hypoglycemia in patients with the Doege-Potter syndrome is surgical excision. We here report that a combination of temozolomide and bevacizumab may be a viable option in patients with inoperable disease.

Low tissue levels of miR-125b predict malignancy in solitary fibrous tumors of the pleura

Background

Solitary fibrous tumors of the pleura (SFTP) are rare neoplasia of the chest. A subset of SFTP follows a malignant course, sometimes several years after complete resection. Traditional scoring systems based on clinical and histological features are poor predictors of biological behavior. This study aimed to investigate tumor-associated miRNAs expression as novel biomarkers to predict the clinical behavior of SFTP.

Methods

Formalin-fixed and paraffin-embedded SFTP tissues blocks from patients surgically resected between 1992 and 2013 at two tertiary care teaching hospitals were included. SFTP tumors were categorized as either malignant or benign variants according to the WHO classification. Following miRNAs levels were measured: let-7a, miR-16b, miR-17, miR-21, miR-31, miR-34a, miR-92a, miR-125a, miR-125b, miR-195-5b, miR-203a, and miR-223. Differential gene expressions which were calculated with the threshold cycle (C_t) method were compared among the two variants.

Results

Thirty-eight patients (40% male, mean age 62.2 (±10.9) years) were included. Expression levels of miR-125b showed a significant difference between benign compared to malignant variants (−3.08 ± 0.93 vs. -2.22 ± 1.36, p = 0.0068). Furthermore, lower levels of miR-125b were found to be associated with increased tumor size (p = 0.0414). Thus, downregulation of miR-125b indicates malignant transformation. All other investigated miRNAs were not associated with grading of SFTP.

Conclusions

Our data suggest a potential role of miR-125b in the pathogenesis of tumor growth and malignant transformation of SFTP, respectively. Further studies have to address the potential use of miRNA-125b as a biomarker or therapeutic target in SFTP.

Malignant solitary fibrous tumor in retroperitoneum: A case report and literature review

RATIONALE

Solitary fibrous tumor (SFT) is a rare mesenchymal tumor occurs in various sites. Malignant SFT in retroperitoneum is extremely rare.

PATIENT CONCERNS

We report a case of malignant retroperitoneal SFT in a 59-year-old man presented with right flank pain for 1 month.

DIAGNOSES, INTERVENTIONS AND OUTCOMES

A laparotomy and resection of the tumor were performed, the histopathologic and immunohistochemical findings were consistent with malignant retroperitoneal SFT. No adjuvant treatment was performed, and the patient had no signs of recurrence or metastasis at the 12 months follow-up.

LESSONS

Complete surgical excision is the basic treatment principle for malignant retroperitoneal SFT. The histologic features and the Ki-67 label index are helpful for the diagnosis of malignant SFT.

Diagnostic immunohistochemistry through Rosai-coloured glasses

Over the past three decades, Immunohistochemistry has materially changed the practice of diagnostic surgical pathology. Foundational observations in this field were critical to a reasoned assessment of both the risks and opportunities that immunohistochemistry afforded the surgical pathologist, and our current practice draws heavily on those early assessments. As we collectively look to and acknowledge those who recognized the value of this technique and who helped guide its development as a companion to (not a replacement for) histomorphologic evaluation, we are drawn to those whose mastery of detail and ability to draw common patterns from seemingly unrelated phenomena helped define the diagnostic power of immunohistochemistry. The focus of this review is on one individual, Dr. Juan Rosai, whose contributions transcend the simple linkage of molecular observations to morphology, recognizing novel patterns in both form and color (the latter often the lovely shades of diaminobenzidine), seemingly viewing our diagnostic world at times through an entirely different lens. By looking at Dr. Rosai's early work in this field, reviewing a selection of his seminal observations, particularly in the Immunohistochemistry of thyroid and thymic neoplasia, revisiting how his special insight is often guided by the work of the early masters of morphology, and how his mentorship of others has helped shaped academic surgical pathology practice, perhaps we can get a glimpse through that lens.

Desmoplastic Fibroblastoma (Collagenous Fibroma)

We report a case of desmoplastic fibroblastoma/collagenous fibroma in a 42-year-old African-American male. The 10 cm tumor mass was located subcutaneously on the right lower back. Grossly, the tumor was firm and well-circumscribed and, on cut surface, had a white and homogeneous appearance. Microscopically, the tumor was composed of medium-sized spindled and stellatefibroblasts sparsely distributed in a densely fibrous background. No significant nuclear pleomorphism, mitotic figures, or necrosis were identified. The tumor cells were diffusely positive for vimentin and factor XIIIa but were negative for all other markers tested. Ultrastructurally, the tumor cells had features of fibroblasts with abundant rough endoplasmic reticulum. No recurrence has been seen at 5 months after excision.

Solitary Fibrous Tumor of the Liver

A rare case of solitary fibrous tumor (SFT) of the liver is described. The patient was a 49-year-old man who had a 17x12xlO cm mass (2,750 g) with a firm and vaguely whorled cut surface, a scar-like central area, and pushing rather than infiltrating borders. It was located in the subcapsular parenchyma of the left lobe. The histologic, immunohistochemical, and ultrastructural features are identical to those seen in the more common SFTs of the pleura. Those features include a variable spindle cell proliferation, scant mitotic activity, immunoreactivity for CD34 and vimentin, and the absence of necrosis. The patient underwent a partial hepatectomy and the surgical margins were free of tumor. No recurrence was detected 15 months after excision. This case adds to 12 similar previously reported cases involving the liver. A review of the literature indicates that SFT of the liver behaves in a benign fashion.

Juxtaglomerular Cell Tumor of the Kidney

We present a case of juxtaglomerular cell tumor (JGCT) that developed in a 44-year-old woman with hypertension, which subsided after the tumor was removed. The tumor was 8.5 cm in greatest dimension and is thought to be the largest such tumor reported to date. Ultrastructural study confirmed the diagnosis of JGCT by the demonstration of the typical cytoplasmic rhomboidal secretory granules on electron microscopy. The tumor cells were also strongly reactive for CD34, a finding that has not been previously reported and that may be an adjunct to the diagnosis of JGCT in a patient with hypertension, hyperreninemia, and/or hypokalemia. At present, however, further studies on additional cases for CD34 expression will be necessary to fully evaluate the diagnostic utility of this marker in the diagnosing of JGCT.

Practical Issues for Retroperitoneal Sarcoma

Background

Retroperitoneal sarcoma is rare. Using initial specimens on biopsy, a definitive diagnosis of histological subtypes is ideal but not always achievable.

Methods

A retrospective institutional review was performed for all cases of adult retroperitoneal sarcoma from 1996 to 2015. A review of the literature was also performed related to the distribution of retroperitoneal sarcoma subtypes. A meta-analysis was performed.

Results

Liposarcoma is the most common subtype (45%), followed by leiomyosarcoma (21%), not otherwise specified (8%), and undifferentiated pleomorphic sarcoma (6%) by literature review. Data from Moffitt Cancer Center demonstrate the same general distribution for subtypes of retroperitoneal sarcoma. A pathology-based algorithm for the diagnosis of retroperitoneal sarcoma is illustrated, and common pitfalls in the pathology of retroperitoneal sarcoma are discussed.

Conclusions

An informative diagnosis of retroperitoneal sarcoma via specimens on biopsy is achievable and meaningful to guide effective therapy. A practical and multidisciplinary algorithm focused on the histopathology is helpful for the management of retroperitoneal sarcoma.

The clinicopathological significance of NAB2-STAT6 gene fusions in 52 cases of intrathoracic solitary fibrous tumors

NAB2-STAT6 gene fusion drives STAT6 nuclear expression and is the pathognomonic hallmark of solitary fibrous tumors (SFTs). However, no study has systematically analyzed the clinicopathological features, STAT6 immunoexpression status, or the fusion variants of NAB2-STAT6 in intrathoracic SFTs. Fifty-two intrathoracic SFTs were retrieved to appraise histopathology, assess STAT6 immunoexpression, and determine NAB2-STAT6 fusion variants by RT-PCR. Location-relevant histologic mimics served as controls. Thirty-one pleura-based, 12 mediastinal/pericardial, and nine intrapulmonary lesions were histologically categorized into eight malignant, eight atypical, and 36 conventional or cellular SFTs, including two fat-forming and two giant cell angiofibroma-like SFTs. STAT6 distinctively decorated the tumoral nuclei in 51 (98%) SFTs. However, no nuclear staining was observed in the histological mimics. NAB2-STAT6 fusion was detected in 34 SFTs. Twenty-nine (85.3%) exhibited the major NAB2ex4-STAT6ex2/3 variant and 5 (14.7%) the minor NAB2ex6-STAT6ex16/17. NAB2ex4-STAT6ex2 was significantly associated with older age (P = 0.01) and pleuropulmonary tumors (P = 0.025). After a median follow-up of 33.9 (range, 0.3-174.6) months, adverse outcomes occurred in one atypical and five malignant SFTs, including two local relapses, one intrapulmonary metastasis, and three extrathoracic metastases. Inferior disease-free survival was univariately associated with atypical/malignant histology (P = 0.001) and a mitosis >4/10 HPFs (P = 0.0012) but was unrelated to fusion variants. In conclusion, the majority of intrathoracic SFTs exhibited STAT6 nuclear staining, and NAB2ex4-STAT6ex2/3 was the predominant fusion type. However, clinical aggressiveness is associated with atypical/malignant histology primarily contributed by increased mitosis but was unrelated to the NAB2-STAT6 fusion variants.

Unusual lesions of the mediastinum

Objectives:

To study unusual lesions in the mediastinum, which do not originate from the thymus, lymph nodes, neural tissues or germ cells, and tissues that normally engender pathologic lesions in the mediastinum.

Materials and Methods:

Of the 65 cases seen, 12 unusual lesion were encountered in a 5½ year period from 2006 to 2011.

Results:

Two cases of nodular colloid goiter and one each of the mediastinal cyst, undifferentiated carcinoma, and Langerhans cell histiocytosis (LCH) affected the anterosuperior mediastinum. In the middle mediastinum, one case each of the mesothelioma, malignant gastrointestinal stromal tumor (GIST), squamous cell carcinoma (SCC), solitary fibrous tumor (SFT), and pleomorphic sarcoma (PS) was seen. One case of meningeal melanocytoma (Mme) and primary pleural liposarcoma (PL) involved the posterior mediastinum. Persistent disease was seen in LCH after 2 years. Of all the cases with malignant lesions, only the patient with SCC was alive after 1 year.

Conclusion:

The cases of primary and SCC, LCH, melanocytoma, liposarcoma and PS, and GIST are unexpected and very rarely have paradigms in the mediastinum. Radiologic impression and knowledge of the compartment where these lesions arose from hardly assisted in arriving at a definitive opinion as the lesions were not typical of this location. A high index of suspicion and the immunohistochemical profile facilitated the final diagnosis.

Giant solitary fibrous tumour of the pleura. Case report and review of the literature

Background

Solitary fibrous tumours of the pleura (SFTP) are rare tumours. They are mostly benign. Only around 12% of them are malign ant. In the initial stage they are mostly asymptomatic and by growing they cause chest pain, irritating cough and dyspnoea on account of the pressure created on the surrounding structures. Rare giant tumours have compression symptoms on the mediastinal structures. The condition requires tiered diagnostic radiology. Preoperative biopsy is not successful in most cases. The therapy of choice is radical surgical tumour removal. Malignant or non-radically removed benign solitary fibrous tumours of the pleura additionally require neoadjuvant therapy.

Case report

A 68-year old patient was hospitalized for giant solitary fibrous tumour of the pleura in the right pleural cavity. With its expansive growth the tumour caused the shift of the mediastinum by compressing the lower vena cava, right cardiac auricle as well as the intermediate and lower lobe bronchus. Due to cardiac inflow obstruction and right lung collapse, the patient’s life was endangered with signs of cardio-respiratory failure. After preoperative diagnostic radiology, the tumour was surgically removed. Postoperatively, the patient’s condition improved. No disease recurrence was diagnosed after a year.

Conclusions

Giant solitary fibrous tumour of the pleura may cause serious and life-threatening conditions by causing compression of the pleural cavity with its expansive growth. Early diagnosis of the condition enables less aggressive as well as video-assisted thoracic surgery in patients with significantly better state of health. Large tumour surgeries in cardio-respiratory affected patients are highly risk-associated procedures.

Mesenchymal tumours of the mediastinum--part I

The mediastinum is an anatomically defined space in which organs and major blood vessels reside with surrounding soft tissue elements. The thymus is an important organ in the mediastinum, and many of the masses encountered in the mediastinum are related to this organ. Most neoplasms diagnosed in the mediastinum are epithelial tumours (thymomas and thymic carcinomas), lymphomas or germ cell tumours. In contrast, soft tissue tumours of the mediastinum are rare. In 1963, Pachter and Lattes systematically reviewed soft tissue pathology of the mediastinum, covering the hitherto described [2, 226, 227] In this review, based on the 2013 WHO classification of soft tissue tumours and the 2015 WHO classification of tumours of the lung, pleura, thymus and heart, we provide an updated overview of mesenchymal tumours that may be encountered in the mediastinum.

Tracing CD34+ Stromal Fibroblasts in Palatal Mucosa and Periodontal Granulation Tissue as a Possible Cell Reservoir for Periodontal Regeneration

The aim of the present research was to trace CD34+ stromal fibroblastic cells (CD34+ SFCs) in the palatal connective tissue harvested for muco-gingival surgical procedures and in granulation tissues from periodontal pockets using immunohistochemical and transmission electron microscopy. Immunohistochemical analysis targeted the presence of three antigens: CD31, α-smooth muscle actin (α-SMA), and CD34. In the palate, CD31 staining revealed a colored inner ring of the vessels representing the endothelium, α-SMA+ was located in the medial layer of the vasculature, and CD34 was intensely expressed by endothelial cells and artery adventitial cells (considered to be CD34+ SFCs). Granulation tissue showed the same pattern for CD31+ and α-SMA, but a different staining pattern for CD34. Ultrastructural examination of the palatal tissue highlighted perivascular cells with fibroblast-like characteristics and pericytes in close spatial relationship to endothelial cells. The ultrastructural evaluation of granulation tissue sections confirmed the presence of neovasculature and the inflammatory nature of this tissue. The present study traced the presence of CD34+ SFCs and of pericytes in the palatal connective tissue thus highlighting once more its intrinsic regenerative capabilities. The clinical and systemic factors triggering mobilization and influencing the fate of local CD34+SCFs and other progenitors are issues to be further investigated.

Solitary fibrous tumor of the pleura: morphogenesis and progression. A report of 36 cases

PURPOSE

We attempted to identify the exact point of tumor eruption of a solitary fibrous tumor of the pleura (SFTP).

METHODS

We morphologically classified 36 SFTPs into 5 categories. Type A showed a connection that included a bloodstream with the pleura on both sides. Type B only showed a connection that included a bloodstream with the visceral pleura, and had a non-bloodstream connection with the parietal pleura. Type C only showed a connection that included a bloodstream with the visceral pleura, and had no connection with the parietal pleura. Type D showed a non-bloodstream connection with the visceral pleura, and only showed a connection that included a bloodstream with the parietal pleura. Finally, type E had no connection with the visceral pleura, and only showed a connection that included a bloodstream with the parietal pleura. The clinicopathological profiles of the tumors were investigated according to their type.

RESULTS

The distribution of the 36 SFTPs was as follows: A (19 %), B (6 %), C (67 %), D (0 %) and E (8 %). The tumors categorized as type A tended to be large in size.

CONCLUSIONS

SFTPs commonly arise from the visceral pleura and in accordance with tumor progression they will form a non-bloodstream connection with the parietal pleura. Finally, a vascular pedicle will arise with the parietal pleura.

STAT6 rabbit monoclonal antibody is a robust diagnostic tool for the distinction of solitary fibrous tumour from its mimics

Recurrent NAB2-STAT6 gene fusions have recently been identified in solitary fibrous tumour by next generation sequencing. Our aim was to examine the sensitivity and specificity of STAT6 immunohistochemistry for solitary fibrous tumour versus other morphologically similar soft tissue tumours. STAT6 expression was evaluated in 54 solitary fibrous tumours of various sites and 99 soft tissue tumours in the histological differential diagnosis. We used a rabbit monoclonal STAT6 antibody (1:100), which has not been reported by others, on formalin fixed, paraffin embedded whole sections and tissue microarray slides. Only nuclear staining of STAT6 was considered positive. Distribution of staining was scored as: 0 (no staining), 1+ (1-25%), 2+ (26-50%), 3+ (>50%). Intensity was scored as weak, moderate or strong. Nuclear STAT6 staining was present in all SFT cases tested (54/54, sensitivity 100%), regardless of histology, anatomical site or CD34 status. The majority of cases showed 3+ and strong staining. All tested cases of cellular angiofibroma (0/9), myofibroblastoma (0/10), spindle cell lipoma (0/10), benign fibrous histiocytoma (0/13), dermatofibrosarcoma protruberans (0/9), low-grade fibromyxoid sarcoma (0/7), schwannoma (0/8), desmoid-type fibromatosis (0/8), monophasic synovial sarcoma (0/11), malignant peripheral nerve sheath tumour (0/7), and mesenchymal chondrosarcoma (0/7) were negative for STAT6 (specificity 100%). Our study further supports the utility of STAT6 immunohistochemistry as an adjunct in the diagnosis of solitary fibrous tumour.

Recurrent intrathoracic solitary fibrous tumor: Remarkable response to radiotherapy

Solitary Fibrous Tumor of the Pleura (SFTP) is an uncommon neoplasm which grows slowly. For some cases, surgery is warranted. However, for unresectable ones, the standard strategy has not been established yet. We presented a rare case of recurrent malignant intrathoracic solitary fibrous tumor. It was impossible to resect the tumor. Radiotherapy alone achieved a significant improvement effect.

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.

Immunohistochemistry of soft tissue tumours - review with emphasis on 10 markers

Immunohistochemistry is an integral component in the proper analysis of soft tissue tumours, and a simple panel of six markers is useful in practical triage: CD34, desmin, epithelial membrane antigen (EMA), keratin cocktail AE1/AE3, S100 protein and alpha smooth muscle actin (SMA). These markers frequently assist in the differential diagnosis of fibroblastic, myoid, nerve sheath and perineurial cell tumours, synovial and epithelioid sarcoma and others. However, they all are multispecific, so that one has to be cognizant of their distribution in normal and neoplastic tissues. Four additional useful markers for specific tumour types are discussed here: CD31 and ERG for vascular endothelial tumours, and KIT and DOG1/Ano-1 for gastrointestinal stromal tumours (GISTs). However, hardly any marker is totally monospecific for any one type of tumour. Furthermore, variably lineage-specific markers do not usually distinguish between benign and malignant proliferations, so that this distinction has to be made on histological grounds. Immunohistochemical evaluation is most useful, efficient and cost-effective when used in the context of careful histological evaluation by an experienced pathologist, aware of all diagnostic entities and their histological spectra. Additional diagnostic steps that must be considered in difficult cases include clinicoradiological correlation and additional sampling of remaining wet tissue, if possible.

Loss of CD34 and high IGF2 are associated with malignant transformation in solitary fibrous tumors

The aim of this study was to characterize the subgroups of solitary fibrous tumor (SFT) and to investigate the expression of different biomarkers including CD34 and IGF2 in malignant transformation. Two hundred and ninety-four (294) SFTs from a single German consultation center of soft tissue tumors were categorized into the new proposal of SFT designation. We found the fibrous variant in 223 (75.9%), the cellular variant in 65 (22.1%), the fat forming variant in 4 (1.4%), and the giant cell-rich variant in 2 (0.6%) cases. Anatomical location, size, mitotic index, necrosis, cellularity, collagenous ropes, and growth pattern of the vessels were recorded. Criteria of malignancy were found in 68 (23%) tumors. Expression of IGF2, IGF1R, CD34, BCL2, CD99, SMA, S100, PanCK, and Ki67 was analyzed immunohistochemically. Low expression of CD34 and high expression of IGF2 were significantly associated with malignant transformation and the metastatic rate. Moreover the presence of necrosis showed the most significant p-value (p<0.004). Of all SFTs, the fibrous variant is the most common, followed by the cellular variant. The fat-forming and giant cell-rich variants are very rare. Low expression of CD34 and high expression of IGF2 are significantly associated with malignant transformation, and might be an interesting target of individualized therapy.

ALDH1 is an immunohistochemical diagnostic marker for solitary fibrous tumours and haemangiopericytomas of the meninges emerging from gene profiling study

Background

Solitary Fibrous Tumours (SFT) and haemangiopericytomas (HPC) are rare meningeal tumours that have to be distinguished from meningiomas and more rarely from synovial sarcomas. We recently found that ALDH1A1 was overexpressed in SFT and HPC as compared to soft tissue sarcomas. Using whole-genome DNA microarrays, we defined the gene expression profiles of 16 SFT/HPC (9 HPC and 7 SFT). Expression profiles were compared to publicly available expression profiles of additional SFT or HPC, meningiomas and synovial sarcomas. We also performed an immunohistochemical (IHC) study with anti-ALDH1 and anti-CD34 antibodies on Tissue Micro-Arrays including 38 SFT (25 meningeal and 13 extrameningeal), 55 meningeal haemangiopericytomas (24 grade II, 31 grade III), 163 meningiomas (86 grade I, 62 grade II, 15 grade III) and 98 genetically confirmed synovial sarcomas.

Results

ALDH1A1 gene was overexpressed in SFT/HPC, as compared to meningiomas and synovial sarcomas. These findings were confirmed at the protein level. 84% of the SFT and 85.4% of the HPC were positive with anti-ALDH1 antibody, while only 7.1% of synovial sarcomas and 1.2% of meningiomas showed consistent expression. Positivity was usually more diffuse in SFT/HPC compared to other tumours with more than 50% of tumour cells immunostained in 32% of SFT and 50.8% of HPC. ALDH1 was a sensitive and specific marker for the diagnosis of SFT (SE = 84%, SP = 98.8%) and HPC (SE = 84.5%, SP = 98.7%) of the meninges. In association with CD34, ALDH1 expression had a specificity and positive predictive value of 100%.

Conclusion

We show that ALDH1, a stem cell marker, is an accurate diagnostic marker for SFT and HPC, which improves the diagnostic value of CD34. ALDH1 could also be a new therapeutic target for these tumours which are not sensitive to conventional chemotherapy.

Risk factor analysis for the recurrence of resected solitary fibrous tumours of the pleura: a 33-year experience and proposal for a scoring system

OBJECTIVES

Surveillance after resection of solitary fibrous tumours of the pleura (SFTP) remains undefined. This study reviews our experience with surgical treatment of SFTP to determine the specific risk factors to predict recurrence.

METHODS

A retrospective review of 59 patients surgically treated for SFTP during the years 1977-2010 was conducted. Clinico-pathological factors for recurrence were analysed by Kaplan-Meier and Cox proportional hazard methods.

RESULTS

The mean age was 57 ± 14 years. There were 32 (54%) men. Among 32 (54%) symptomatic patients, chest pain (22%), cough (19%) and dyspnoea (17%) were most frequent. The mean tumour size was 7.3 ± 6.7 cm, and 14 patients had SFTPs larger than 10 cm. An SFTP was pedunculated in 38 (67%) cases and had a visceral origin in 40 (68%). Paraneoplastic syndromes were observed in 3 (5%) patients. On histopathologic analysis, 4 (7%) presented ≥ 4 mitosis/10 high-power fields (HPFs), 8 (15%) atypia, 14 (24%) hypercellularity and 6 (10%) necrosis. After a mean follow-up of 8.8 ± 7.0 years, we observed 8 (14%) recurrences; median time to recurrence was 6 years (range 2-16 years). Two (3%) patients received adjuvant therapy. We constructed a predictive score for recurrence by assigning one point to each of the six variables: parietal (vs visceral) pleural origin, sessile (vs pedunculated) morphology, size >10 cm (vs <10 cm), the presence of hypercellularity, necrosis and mitotic activity ≥ 4/HPF (vs <4). A score of ≥ 3 best predicted recurrence (sensitivity: 100%, specificity: 92%, area under receiver operating characteristic curve = 0.966, P < 0.0001). With a score of ≥ 3, recurrence-free survival was 80%, 69, 23 and 23% at 3, 5, 10 and 15 years, whereas a score of <3 was 100% up to 15 years. Our scoring system was superior in predicting malignant behaviour and recurrence compared with England's criteria or de Perrot staging.

CONCLUSIONS

The proposed scoring system is simple, easily obtained from existing pathological description and reliably predicts recurrence in this patient population harbouring SFTP. The SFTP score may stratify patient risk and guide postoperative surveillance. We recommend validation in additional clinical series.

Locally infiltrative ameloblastic fibroma in a rhesus macaque (Macaca mulatta) with characterizations of its proliferating activity and biological behavior

An 8-year-old male rhesus macaque (Macaca mulatta) presented with unilateral enlargement of the left mandible. Radiographs revealed a marked expansion of the left mandible with a multilocular radiolucent mass with abundant osteolysis. The mass was grossly firm, fleshy, and gelatinous on the cut surface. Histologically, the mass was locally infiltrative and composed of neoplastic epithelial and mesenchymal components that stained positive for cytokeratin and vimentin, respectively. Occasional densely spherical condensations of fibroblasts resembling the cap stage of odontogenesis were present in the mesenchyma. Immunohistochemical staining with Ki-67, S-100, and CD34 indicated that both epithelial and mesenchymal components of the neoplasm had low proliferation. Alcian blue, periodic acid-Schiff, and trichrome stains showed an immature stromal component with no collagen formation. Based on the clinical, histologic, and immunophenotypic features, the tumor was identified as a locally infiltrative ameloblastic fibroma.

Neoplastic and nonneoplastic benign mass lesions of the lung

While most lung neoplasms are malignant, a subset of true neoplasms are benign, the most common of which are pulmonary hamartomas. In addition, a substantial proportion of lung mass lesions are nonneoplastic; granulomas are among the commonly encountered nonneoplastic masses. There is also a group of relatively rare, mainly inflammatory and fibrous tumor-like lesions that are encountered on core biopsy and excisions of lung tissue.

Solitary fibrous tumors of the pleura

PURPOSE OF REVIEW

Solitary fibrous tumor of the pleura (SFTP) is a rare neoplasm of the pleura. Although an increasing number of case series have been reported in recent years, so far clinical behavior is still unpredictable. The following article presents a detailed review of the recent larger series of SFTP with particular attention to the clinical presentation, pathologic characteristics and surgical features in order to define more precisely the long-term outcome after treatment of this rare entity.

RECENT FINDINGS

Usually, after a complete surgical resection a very long survival could be expected in almost all cases. However, the preoperative detection and management of malignant SFTPs are still challenging issues.

SUMMARY

SFTP remains an enigmatic tumor. Clinical and radiological assessment is often unsatisfactory to obtain a definitive diagnosis. Benign SFTPs are almost always cured with complete surgical resection, and in cases of recurrence the re-do resection of benign recurrences is usually curative. Long-term survivals are also possible for malignant SFTPs, although a higher recurrence rate and higher tumor-related mortality can be expected in these cases. Histologic characteristics distinguishing benign from malignant variants are crucial in estimating the risk of recurrence and planning adjuvant therapies.

"Hitting all the right markers to save a life" Solitary fibrous tumors of the central nervous system: Case series and review of the literature

Background:

Solitary fibrous tumors (SFTs) of the central nervous system are uncommon. Their biological features remain largely unknown; hence, the clinical management and prognosis is often challenging due to the lack of comprehensive data. For this reason, we present two cases of large SFTs to illustrate a comprehensive review.

Methods:

This was a retrospective analysis of two patients: a 65-year-old male with a left parietooccipital lesion and a 70-year-old female with a right parietal convexity mass.

Results:

Gross total resection was performed in the male patient with no recurrence 30 months after resection. The second patient received stereotactic radiosurgery for what was initially thought to be a parafalcine meningioma; however, continued growth 1 year later prompted an open resection, with pathology indicative of an SFT. The tumor recurred the following year requiring repeat resection. Unfortunately, due to the aggressive nature of the lesion, the patient eventually succumbed to tumor burden a year later.

Conclusion:

Based on the literature review, the sometimes observed aggressive growth pattern, and also, the potential for malignant transformation, we recommend complete resection of SFTs with close sequential follow-up.

A locally aggressive solitary fibrous tumor of the leg: Case report and literature review

INTRODUCTION

The solitary fibrous tumor (SFT) is a rare soft tissue tumor with a substantially benign clinical behavior. However, malignant neoplasms with local recurrence or distant metastases have been reported.

PRESENTATION OF THE CASE

The authors present a case of an aggressive SFT of the leg, in a 55 years old Caucasian man. Radiological, histological and molecular findings are reported. The differential diagnosis, therapy and outcome of this rare tumor are also discussed.

DISCUSSION

An extensive review of literature showed SFT's clinical behavior as substantially benign, anyway aggressive or malignant neoplasms have been described. The potential risk of local recurrence and distant metastasis thus suggests wide surgical resection and careful long-term follow-up. Differential diagnosis may be quite laborious as SFT can mimic a variety of benign and malignant mesenchymal tumors; immunohistochemical analysis for CD34, CD99, vimentin and bcl-2 is then mandatory.

CONCLUSION

Our clinical experience confirmed that SFT may have an aggressive behavior, however, conservative surgical treatment may be successful in the long term.