Translocation 2;11 in a fibroma of tendon sheath

Fibroma of tendon sheath is defined by a USP6 gene fusion-morphologic and molecular reappraisal of the entity

Fibroma of tendon sheath (FTS) is an uncommon benign myofibroblastic neoplasm that arises in association with tenosynovial tissue. Fusions of the USP6 gene have been recently documented in a proportion of so-called "cellular FTS" but not in "classic FTS". It remains unknown whether FTS can be defined by a USP6 fusion, regardless of cellularity, and what are USP6 fusion-negative "cellular FTS". Furthermore, FTS with low cellularity seems to be frequently confused with desmoplastic fibroblastoma. We performed a comprehensive analysis, including targeted RNA sequencing, of 58 consecutive cases originally diagnosed as FTS (n = 49), desmoplastic fibroblastoma (n = 6), or nodular fasciitis (n = 3); the latter two at the predilection sites for FTS. After review of the original slides, 28 lesions were morphologically classified as FTS (13 "classic" and 15 "cellular") and 23 as desmoplastic fibroblastoma. Among originally diagnosed FTS at the more cellular end of the spectrum, we identified seven lesions that shared many morphologic features of FTS but, in addition, showed several distinct morphologic features consistent with myofibroma, such as myoid appearance, branching thin-walled vessels, and perivascular growth. Targeted RNA sequencing showed a USP6 fusion in 17 of 18 analyzed FTS, regardless of cellularity, 0 of 5 desmoplastic fibroblastomas and 0 of 4 myofibromas. MYH9, COL1A1, and ASPN were identified as fusion partners in three cases each, and MIR22HG, CTNNB1, SPARC, CAP1, EMP1, LINC00152, NR1D1, and RAB1A in a single case each. FTS, regardless of cellularity, can be defined by a USP6 fusion with a variety of fusion partners. More cellular lesions exhibiting some morphologic features of FTS but lacking a USP6 fusion tend to be myofibromas.

Molecular Alterations in Pediatric Fibroblastic/Myofibroblastic Tumors: An Appraisal of a Next Generation Sequencing Assay in a Retrospective Single Centre Study

BACKGROUND

Pediatric fibroblastic/myofibroblastic tumors (PFMTs) can be challenging to definitively classify. Large case series or diagnostic updates have not been recently published despite identification of molecular alterations that could improve diagnostic accuracy. Our review of the literature found that over two-thirds of the more than 30 types of PFMTs harbor recurrent molecular alterations. We performed an institutional review of PFMTs to highlight limitations of a predominantly morphological classification, and evaluated the utility of a next-generation sequencing assay to aid diagnosis.

METHODS

PFMTs identified over a period of 12 years were reviewed, categorized per the new WHO classification, and tested using the Oncomine Childhood Cancer Research Assay.

RESULTS

Eighty-seven specimens from 58 patients were reviewed; 50 were chosen for molecular analysis, 16 (32%) lacking definitive classification. We identified alterations, some novel, in 33% of assayed cases. Expected alterations were identified for most known diagnoses and mutations were identified in 6 of 16 tumors (38%) that were initially unclassified.

CONCLUSION

We confirmed a significant subset of PFMTs remain difficult to classify using current criteria, and that a combined DNA/RNA assay can identify alterations in many of these cases, improving diagnostic certainty and suggesting a clinical utility for challenging cases.

An Update on Clinicopathological, Imaging and Genetic Features of Desmoplastic Fibroblastoma (Collagenous Fibroma)

Desmoplastic fibroblastoma (also known as collagenous fibroma) is an uncommon benign fibroblastic/myofibroblastic neoplasm that primarily arises in the subcutaneous tissue of upper extremity. Magnetic resonance imaging reveals a well-defined mass in intimate association with dense connective tissue and prominent low signal intensity on all pulse sequences. Peripheral and septal enhancement is usually seen after intravenous contrast. Histologically, the lesion is paucicellular and consists of spindle to stellate-shaped cells embedded in a collagenous or myxocollagenous stroma with low vascularity. Diffuse and strong nuclear immunoreactivity for FOS-like antigen 1 seems to be characteristic of desmoplastic fibroblastoma. Cytogenetic studies have demonstrated the presence of 11q12 rearrangements and an identical t(2;11)(q31;q12) translocation. This review provides an updated overview of the clinical, radiological, histological, cytogenetic and molecular genetic features of desmoplastic fibroblastoma and discusses the relationship to fibroma of tendon sheath.

The Unusual Case of Fibroma of Tendon Sheath in a Young Girl with Turner Syndrome Undergoing Growth Hormone Treatment

Fibroma of tendon sheath (FTS) is an uncommon mass that arises from the tendon sheath of extremities. The tumor typically affects adults between ages 20 and 50 years with a predominance in males. To date, growth hormone (GH) treatment is safe for children with Turner syndrome without risk factors and is accepted worldwide. This article reports the case of a nine-year-old female patient with Turner syndrome and FTS during GH treatment. She had been treated with daily subcutaneous GH to improve growth failure with a mean dose of 0.28 mg/kg/week and the level of insulin-like growth factor-1 was within the normal range. During the follow-up period, she complained about a mass in her hand, subsequently diagnosed as FTS. This report illustrates the clinical impact of Turner syndrome and GH treatments on the occurrence of this tumor through literature reviews. Further studies are needed to highlight the association between FTS and GH treatment, especially in Turner syndrome.

Ubiquitin-specific Peptidase 6 (USP6)-associated Fibroblastic/Myofibroblastic Tumors: Evolving Concepts

Ubiquitin-specific peptidase 6 (USP6) is a hominoid-specific gene residing on chromosome 17p13 and serves as a deubiquitinating enzyme with a diverse set of functions including intracellular trafficking, inflammatory signaling, cell transformation and protein turnover. USP6 rearrangements were first identified in aneurysmal bone cysts, resulting in promoter swapping and over-expression of wild type USP6. Several morphologically overlapping fibroblastic/myofibroblastic tumors are known to harbor USP6 rearrangements, including nodular fasciitis, cellular fibroma of tendon sheath, myositis ossificans and fibro-osseous pseudotumor of digits. Over the past few years, fusions involving the USP6 gene and various partner genes have been described in these neoplasms. The current World Health Organization Classification of Tumors of Soft Tissue suggests that USP6-rearranged lesions are typically benign and usually self-limited in their growth. This review provides an updated overview of the clinical, histological and molecular genetic features of USP6-associated fibroblastic/myofibroblastic tumors and discusses how these lesions should be best classified.

Characterization of novel USP6 gene rearrangements in a subset of so-called cellular fibroma of tendon sheath

Fibroma of tendon sheath (FTS) is an uncommon benign fibroblastic/myofibroblastic neoplasm that typically arises in the tenosynovial tissue of the distal extremities. Histologically, it is a well-circumscribed proliferation of spindle cells within collagenous stroma with peripheral slit-like vessels. Most examples are relatively hypocellular and more densely collagenous than nodular fasciitis; however, a cellular variant has been described, which has considerable morphologic overlap with nodular fasciitis and has been shown to harbor USP6 translocations in a subset of cases. The incidence of these rearrangements and the identity of the USP6 fusion partners have not been described in detail. In this study we evaluate 13 cases of cellular fibroma of tendon sheath by anchored multiplex PCR/next generation sequencing in order to detect potential gene fusions. Nucleic acids of adequate quality were obtained in 11 cases, demonstrating gene fusions in 7/11 (64%), all of which involve USP6 with a variety of partners, including PKM, RCC1, ASPN, COL1A1, COL3A1, and MYH9. Some unusual histomorphologic findings were present in a subset of cases including palisading growth pattern, epithelioid cells, and osteoclast-like multinucleated giant cells, particularly in the tumors with PKM and ASPN gene partners. Overall, the findings support a biologic relationship between cellular fibroma of tendon sheath and other lesions within the spectrum of USP6-rearranged neoplasms, particularly nodular fasciitis.

Fibroma of tendon sheath of the hand in a 3-year-old boy: a case report

BACKGROUND

Fibroma of tendon sheath (FTS) is a rare benign soft tissue tumor that often occurs in the upper extremities. It manifests as a slow-growing mass, often without tenderness or spontaneous pain. FTS occurs most commonly in people aged 20-40 years and is extremely rare in young children. Because FTS presents with atypical physical and imaging findings, it might be misdiagnosed as another soft tissue tumor such as a ganglion cyst or tenosynovial giant cell tumor (TSGCT). Although marginal resection is usually performed, a high rate of local recurrence is reported.

CASE PRESENTATION

A boy aged 3 years and 1 month visited our outpatient clinic with a complaint of a mass of the left hand. An elastic hard mass approximately 20 mm in diameter could be palpated on the volar side of his left little finger. This mass was initially diagnosed as a ganglion cyst at another hospital. Ultrasonography revealed a well-circumscribed hypoechoic mass with internal heterogeneity on the flexor tendon. On magnetic resonance imaging (MRI), the mass showed iso signal intensity to muscle on T1-weighted images, and homogeneously low signal intensity to muscle on T2-weighted images. The mass was peripherally enhanced after contrast administration. FTS was initially suspected as the diagnosis on the basis of these imaging features. Because of the limited range of motion of his little finger, surgery was performed when he was 4 years old. Histopathological findings indicated the mass was well-circumscribed and contained scattered spindle cells embedded in a prominent collagenous matrix. The spindle cells contained elongated and cytologically bland nuclei with a fine chromatin pattern. Nuclear pleomorphism and multinucleated giant cells were not observed. On the basis of these findings, we made a diagnosis of FTS. One year after surgery, no signs of local recurrence were observed.

CONCLUSIONS

We experienced an extremely rare case of FTS in the hand of a 3-year-old child. We especially recommend ultrasonography for hand tumors of young children to diagnose or eliminate ganglion cysts. MRI helped differentially diagnose FTS from TSGCT. Although marginal resection can be performed as a treatment, great care should be taken postoperatively because FTS has a high possibility of local recurrence.

USP6-Associated Neoplasms: A Rapidly Expanding Family of Lesions

Nearly 20 years ago, the first description of a translocation involving chromosome 17 on which USP6 resides was described. Since then, not only the culprit gene but also many fusion partners, leading to transcriptional activation of USP6, have been detected. The first neoplasm known to harbor USP6 rearrangements was aneurysmal bone cyst. Since then, other entities like nodular fasciitis, myositis ossificans, fibro-osseous pseudotumor of digits, and a subgroup of fibromas of tendon sheath, probably representing tenosynovial nodular fasciitis, have been added to the list of USP6-rearranged lesions. Remarkably, all of them share clinical as well as morphological characteristics, and authors have suggested that these entities actually belong to the same spectrum. This review summarizes the current knowledge regarding USP6-rearranged lesions and further elaborates on how these neoplasms relate to one another. We propose to call these lesions UAN (Usp6-associated neoplasm).

A Case of 14-Year-Old Male with Fibroma of Tendon Sheath of the Hand with Novel Chromosomal Translocation 4;10

Fibroma of tendon sheath (FTS) is an uncommonly encountered soft tissue mass, which is morphologically distinct from the more commonly seen giant cell tumor of tendon sheath (GCTTS). Initially described in 1936, FTS is typically a slow growing, painless, firm mass with a predilection for the upper extremity, frequently involving the hand. Cases of associated triggering or compression neuropathies have been described when underlying tendons or nerves are affected. Currently, the literature on FTS is sparse and largely limited to case reports. More recently, few reports of cytogenetic analysis on FTS have been reported in the literature. Cellular and chromosomal analysis of FTS tissue revealed chromosomal translocations with yet unknown clinical significance. Here, we present a case report of FTS in a 14-year-old male with a painless enlarging mass on the palmar side of the left hand treated by excision. Subsequent karyotypic analysis revealed a chromosomal translocation t(4;10) (p16;q24), add (10)(q22)[24]. To our knowledge, this is the first description of this chromosomal aberration in the literature.

Superficial radial nerve compression due to fibroma of the brachioradialis tendon sheath: A case report

Fibroma of the tendon sheath (FTS) is a rare benign tumour that usually develops in the upper extremity, particularly in the fingers, hands and wrists. Herein, we present the case of a patient with an unusually localised FTS compressing the superficial branch of the radial nerve. A 62-year-old woman presented with a superficial radial nerve compression due to FTS of the brachioradialis. Histopathological diagnosis was confirmed as a FTS after marginal excision. The patient who had compression-related symptoms in the superficial branch of the radial nerve recovered completely at one month after surgery. One year later, the patient remained free of symptoms and no recurrence was observed.

Hip Arthroscopic Resection of an Intra-Articular Fibroma of the Tendon Sheath

Fibroma of the tendon sheath most often presents around small joints and involves the tendon and tendon sheaths of the fingers, hands, and wrist. In rare instances, it presents as an intra-articular mass. It has never been described in the hip joint. In the current case presentation, this benign tumor was found to be the source of a patient's atypical severe hip pain. Arthroscopic resection of this tumor alleviated the patient's pain.

Fibroma of tendon sheath around large joints: clinical characteristics and literature review

Background

Fibroma of tendon sheath (FTS) is a benign tumor arising from the synovium of the tendon sheath that occurs mostly around small joints such as the fingers, hands, and wrist. However, FTS rarely arises around a large joint (knee, shoulder, elbow, and ankle) with intra-articular or extra-articular involvement. The clinical characteristics of FTS arising around a large joint are unclear. An additional 3 cases of FTS arising around a large joint are presented. Furthermore, the published cases and the present cases are reviewed with respect to their clinical characteristics and imaging and histopathology findings.

Methods

The 43 reported cases including the present 3 patients were summarized, and the patients’ profiles, symptoms, sites and locations in the joint involved by FTS, magnetic resonance imaging (MRI) findings, surgical procedures, clinical courses, and cytogenetic analyses were reviewed.

Results

The average age of 26 cases was 40.9 years (range 13–69 years), and about 60% of the patients were male. About 10% of the patients had a past history of trauma to the knee joint. Of the present 3 cases, one case was extra-articular around the elbow joint, one case was extra-articular around the knee joint, and one case was intra-articular involving the knee joint. The common symptoms were pain (62.5%), swelling or palpable mass (54.2%), and limited range of motion of the involved joint (50%). The most commonly involved joint was the knee, with 32 cases (74.4%), followed by the elbow in 5 cases (11.6%), ankle in 4 (9.3%), and shoulder in 2 (4.7%). The tumor typically exhibited iso to low signal intensity on T1-weighted MRI. T2-weighted images showed various patterns, but mostly low signal intensity relative to muscle. The surgical margin was marginal resection in all cases. There were no recurrences after surgery. On chromosomal analysis, only the present Case 3 showed an abnormality.

Conclusions

A total of 43 FTS cases that occurred around large joints were summarized. The most common site was around the knee joint. In FTS cases around large joints, it is necessary to distinguish between various fibroblastic and/or fibrohistiocytic tumors.

Arthroscopic Removal of Suprapatellar Fibroma of Tendon Sheath

Intra-articular fibroma of tendon sheath is a rare disease. To our knowledge, less than 20 cases have been reported in the literature, and none of them was a Chinese patient. In this case report, we present a Chinese patient with intra-articular fibroma of tendon sheath of the knee joint which was excised arthroscopically. We also summarized the clinical presentation, diagnosis, and subsequent management of intra-articular fibroma of tendon sheath.

FOSL1 immunohistochemistry clarifies the distinction between desmoplastic fibroblastoma and fibroma of tendon sheath

AIMS

Although desmoplastic fibroblastoma (DFB) and fibroma of tendon sheath (FTS) are well-established entities, they may show overlapping clinicopathological features. In addition, cytogenetic data showing a shared 11q12 rearrangement in a small number of cases suggest a close link between these entities. A recent microarray study revealed up-regulation of FOSL1 mRNA in DFBs with 11q12 rearrangement. The aim of this study was to clarify the relationship between DFB and FTS.

METHODS AND RESULTS

We tested 42 cases diagnosed originally as either DFBs or FTSs for interobserver concordance based on the existing histological criteria and correlated the diagnosis with FOSL1 immunohistochemistry. In addition, FOSL1 gene status was determined by chromogenic in-situ hybridization (CISH). Using joint histological evaluation, 41 of 42 tumours were classified unanimously by three pathologists into 25 DFBs and 16 FTSs, whereas only one case received discordant opinions. Immunohistochemically, all DFBs showed diffuse, strong FOSL1 nuclear immunoreactivity (25 of 25, 100%), while none of the FTSs showed such overexpression. None of the selected 42 DFB mimics overexpressed FOSL1. FOSL1 was not rearranged in seven DFBs tested by CISH.

CONCLUSIONS

We confirm here that DFB and FTS are two distinct entities that can be distinguished using the existing histological criteria. This distinction corresponds perfectly with FOSL1 immunohistochemical expression status, and diffuse strong FOSL1 expression specific to DFBs sharpens the border between the two categories. FOSL1 overexpression in DFB may not be caused directly by FOSL1 gene rearrangement. FOSL1 may also be a diagnostic aid for differentiating DFB from other histological mimics.

Acral manifestations of soft tissue tumors

This group of biologically diverse entities is united by topographic localization to the hands and feet. Categorizing tumors by body site narrows the differential into a short list of possibilities that can facilitate accurate and rapid diagnosis. The goal of this review is to provide a practical approach to soft tissue tumors of acral locations for clinicians, pathologists, and researchers alike. What ensues in the following text is that tight coupling of the clinical picture and histopathologic findings should produce the correct diagnosis, or at least an abbreviated differential. The salient clinicopathologic, immunohistochemical, and molecular features are presented alongside current treatment recommendations for each entity.

USP6 genetic rearrangements in cellular fibroma of tendon sheath

Fibroma of tendon sheath is a benign (myo)fibroblastic neoplasm of the tenosynovial soft tissues, typically affecting the distal extremities. It is classically described as a paucicellular, densely collagenized tumor; however, cellular variants have been described. A subset of cellular fibromas of tendon sheath shares similar histological features with nodular fasciitis. As nodular fasciitis very frequently harbors rearrangement of ubiquitin-specific peptidase 6 (USP6), we hypothesized that cellular fibromas of tendon sheath with nodular fasciitis-like features may also contain USP6 rearrangements. Cases of fibroma of tendon sheath (n=19), including cellular (n=9) and classic (n=10) variants, were evaluated for USP6 rearrangement by fluorescence in situ hybridization studies. A subset of cases was tested for MYH9 rearrangements and MYH9-USP6 and CDH11-USP6 fusion products. Classic fibroma of tendon sheath occurred in 5 males and 5 females (median age 67 years, range 23-77 years) as soft tissue masses of the hand (n=4), finger (n=3), forearm (n=1) and foot (n=2). Cellular fibroma of tendon sheath occurred in 5 males and 4 females in a younger age group (median age 32 years, range 12-46 years) as small soft tissue masses of the finger (n=5), hand (n=3) and wrist (n=1). USP6 rearrangements were detected in 6/9 cellular fibromas of tendon sheath. Among cellular fibromas of tendon sheath with USP6 rearrangements, no MYH9 rearrangements were detected. By RT-PCR, neither the MYH9-USP6 or the CDH11-USP6 fusion products were detected in any case. Neither USP6 nor MYH9 rearrangement were detected in any classic fibroma of tendon sheath. We report for the first time the presence of USP6 rearrangements in a subset of cellular fibroma of tendon sheath. Based on the similar morphological and molecular genetic features, we suspect that a subset of cellular fibromas of tendon sheath are under-recognized examples of tenosynovial nodular fasciitis, driven by alternate USP6 fusion genes. Further investigation will delineate how these lesions should best be classified.

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.

Benign soft-tissue lesions of the fingers: radiopathological correlation and clinical considerations

Soft-tissue lesions of the fingers are commonly found in daily clinical practice. A wide range of tumors and pseudotumors have been described in this location, and the majority of them are benign. Ganglion cysts are the most common entity, and the localized type of tenosynovial giant cell tumors are the most frequent solid condition. Both may be easily recognized owing to their typical clinical and radiological characteristics. However, categorization of the spectrum of soft-tissue lesions of the fingers remains limited, despite imaging development, and many patients undergo surgery before radiological or histological diagnosis. Clinical history, radiographic features, and ultrasound and magnetic resonance patterns may help in obtaining the correct diagnosis or reducing the list of differential diagnoses. Radiologists should be familiar with imaging findings so that they can determine the size, extension, and affected neighboring anatomical structures, and provide information that allows adequate presurgical counseling.

Intra-articular fibroma of tendon sheath arising in the acromioclavicular joint

Fibroma of the tendon sheath, a rare benign soft tissue tumor that most often occurs in the distal upper extremities (hands and wrist), is exceedingly rare to present as an intraarticular mass. Presented here is the first case in the English literature, to our knowledge, of a fibroma of the tendon sheath arising in the acromioclavicular joint. The patient presented with recurrent shoulder pain with activity without antecedent trauma. Radiographs were essentially normal. MR images demonstrated a lobulated, heterogeneous mass with contrast enhancement arising from the acromioclavicular joint. Following surgical resection, histopathology revealed hypocellular collagen matrix with spindle-shaped fibroblasts, confirming the diagnosis of fibroma of tendon sheath. The imaging features of the fibroma of the tendon sheath and a brief review of the literature are presented.

Fibroma of tendon sheath located within Kager's triangle

The formation of a fibroma of the tendon sheath, a rare, slow-growing, benign tumor, usually occurs in the upper extremities of young adult males. We present an extremely rare case of a fibroma of the tendon sheath arising adjacent to the Achilles tendon within Kager's triangle in a 41-year-old female. The patient presented with progressive pain localized to the posterior aspect of the left ankle. Complete excision and histopathologic analysis of the fibroma were performed. The patient experienced an uneventful recovery after the intervention and had no evidence of recurrence after 3 months of follow-up. Fibroma of the tendon sheath should be included in the differential diagnosis when a patient presents with a painful soft tissue mass in Kager's triangle.

Fibroma of tendon sheath of the hand: a series of 20 patients with 23 tumours

Fibroma of tendon sheath is an uncommon fibrous tumour that has a predilection for the hand. Large series from Histopathological Units report a local recurrence rate of 24% after surgical excision. In the hand/orthopaedic surgery literature, fibroma of tendon sheath was generally reported as isolated case reports with unusual presentations, such as triggering and carpal tunnel syndrome. The current article reports on a series of 23 tumours of the hands of 20 patients. These were all adults (mean age of 36 years) with a male to female ratio of 3:1. The thumb and index were the most common sites. A slow-growing painless mass was the clinical presentation in every case. Total surgical excision was ensured by excision of part of flexor sheath/palmar fascia to which the tumour was attached. Diagnosis was confirmed by the classic histological features of fibroma of tendon sheath. There were no recurrences at final follow-up 2-5 years after surgery.

Updates on the cytogenetics and molecular cytogenetics of benign and intermediate soft tissue tumors

SOFT TISSUE TUMORS ARE CLASSIFIED ACCORDING TO THEIR HISTOLOGICAL RESEMBLANCE TO NORMAL ADULT TISSUES AND CAN BE GROUPED INTO THE FOLLOWING CATEGORIES BASED ON METASTATIC POTENTIAL: benign, intermediate (locally aggressive), intermediate (rarely metastasizing) and malignant. Over the past two decades, considerable progress has been made in our understanding of the genetic background of soft tissue tumors. Traditional laboratory techniques, such as cytogenetic analysis and fluorescence in situ hybridization (FISH), can be used for diagnostic purposes in soft tissue pathology practice. Moreover, cytogenetic and molecular studies are often necessary for prognostics and follow-up of soft tissue sarcoma patients. This review provides updated information on the applicability of laboratory genetic testing in the diagnosis of benign and intermediate soft tissue tumors. These tumors include nodular fasciitis, chondroid lipoma, collagenous fibroma (desmoplastic fibroblastoma), giant cell tumor of tendon sheath (GCTTS)/pigmented villonodular synovitis (PVNS), angiofibroma of soft tissue, myxoinflammatory fibroblastic sarcoma (MIFS) and ossifying fibromyxoid tumor (OFMT).

Fibroblastic and myofibroblastic tumors in children and adolescents

Fibroblastic and myofibroblastic tumors in children and adolescents are a relatively common group of soft tissue proliferations that range from reactive to hamartomatous to neoplastic, with a full spectrum of benign, intermediate, and malignant neoplasms. These lesions are diagnostically challenging because of morphologic and immunohistochemical overlap, despite significant clinical, genetic, and prognostic differences. The fibromatoses are a major subgroup, and all types of fibromatoses can occur in the 1st 2 decades of life. Intermediate and malignant fibroblastic-myofibroblastic tumors are an important group that includes variants of fibrosarcoma and other tumors with recurrent cytogenetic or molecular genetic abnormalities and low metastatic potential. Pathologic examination is enhanced by adjunct techniques, such as immunohistochemistry, cytogenetics, and molecular genetics, although morphology provides the ultimate criteria for a specific diagnosis. This article reviews the clinicopathologic features of fibroblastic and myofibroblastic tumors with an emphasis on the unique aspects of these neoplasms in children and adolescents, the use of diagnostic adjuncts, and differential diagnoses.

FOSL1 as a candidate target gene for 11q12 rearrangements in desmoplastic fibroblastoma

Desmoplastic fibroblastoma (DF) is a benign fibroblastic/myofibroblastic tumor. Cytogenetic analyses have revealed consistent rearrangement of chromosome band 11q12, strongly suggesting that this region harbors a gene of pathogenetic importance. To identify the target gene of the 11q12 rearrangements, we analyzed six cases diagnosed as DF using chromosome banding, fluorescence in situ hybridization (FISH), single-nucleotide polymorphism array and gene expression approaches. Different structural rearrangements involving 11q12 were found in five of the six cases. Metaphase FISH analyses in two of them mapped the 11q12 breakpoints to an ~20-kb region, harboring FOSL1. Global gene expression profiling followed by quantitative real-time PCR showed that FOSL1 was expressed at higher levels in DF with 11q12 rearrangements than in desmoid-type fibromatoses. Furthermore, FOSL1 was not upregulated in the single case of DF that did not show cytogenetic involvement of 11q12; instead this tumor was found to display a hemizygous loss on 5q, including the APC (adenomatous polyposis coli) locus, raising the possibility that it actually was a misdiagnosed Gardner fibroma. 5'RACE-PCR in two 11q12-positive DF did not identify any fusion transcripts. Thus, in agreement with the finding at chromosome banding analysis that varying translocation partners are involved in the 11q12 rearrangement, the molecular data suggest that the functional outcome of the 11q12 rearrangements is deregulated expression of FOSL1.

Fibroma of the flexor hallucis longus tendon sheath

Fibroma of tendon sheath is a rare benign tumor that usually occurs in upper extremities. It is mostly asymptomatic and grows slowly within the tendons or tendon sheaths. Histopathologic findings show well-demarcated nodules consisting of haphazardly arranged fibroblast-like spindle cells, which are embedded in a dense, collagenous matrix. We present a patient with fibroma of the tendon sheath on the flexor hallucis longus tendon, which was in an unusual location and has never been reported. The lesion was completely excised and showed no evidence of recurrence after 2 years of follow-up.

Multiple fibromas of tendon sheath: unusual presentation

Fibroma of the tendon sheath is an uncommon soft tissue tumor presenting as a solitary, slow-growing, firm, painless, small nodule, which shows strong attachment to the tendon or tendon sheath. It is usually localized on fingers and hand tendons in adults between the age of 20 and 40 years old. This case concerns a 61-year-old man presenting with a 5-year history of multiple cutaneous nodules on both palms and soles. Skin biopsy confirmed fibroma of the tendon sheath. Blood tests showed a high titer of rheumatoid factor and positivity to anti-nuclear antibody. No case of fibroma of the tendon sheath occurring multifocally on both palms and soles has been previously reported. Herein, we report on a very rare case of multiple fibromas of the tendon sheath arising from palms and soles, which supports the pathogenetic hypothesis that this tumor may be a reactive process rather than a true neoplasm.

Tumors and diseases of the joint

A variety of different diseases affect the synovium, including infection, noninfectious immunologic inflammatory conditions, degenerative arthroses, crystal deposits, trauma, and tumors. Tumors of the synovium are relatively uncommon. Any mesenchymal tumor may arise in the synovium, but most recapitulate its normal counterpart including synoviocytes, blood vessels, fat, and fibrous tissue. These tumors can arise in any synovial lined structures both within joints and in extraarticular locations. Most synovial tumors are benign. Malignant tumors are rare but important to recognize because many are aggressive and must be treated appropriately. Among common nonneoplastic conditions that affect the synovium and surrounding structures are crystal deposits such as monosodium urate crystals, calcium pyrophosphate dihydrate crystals, and hydroxyapatite crystals. These crystal deposits may be asymptomatic or cause severe pain or chronic joint destruction. Their accurate identification is important to guide appropriate therapy.

Clonal complex chromosome aberration in non-ossifying fibroma

Cytogenetic information of non-ossifying fibromas (NOFs) is exceptionally limited. This fact relies, in part, on their benign nature but mainly because most cases evolve undetected or there is no need for surgical intervention. We report the case of a NOF arising in the left tibia of a 14-year-old male with an invariable clonal translocation. The karyotype was denoted as 42-46,XY,t(11;3;14)(q23;p21;p11). There are only two previous reported cases of clonally aberrant NOF. Records from additional cases will be essential to assess whether consistent karyotypic aberrations define this lesion.

Collagenous fibroma (desmoplastic fibroblastoma) with a new translocation involving 11q12: a case report

Collagenous fibroma (or desmoplastic fibroblastoma) is a rare, benign tumor usually centered in the subcutaneous tissue composed of spindle-shaped to stellate fibroblasts and myofibroblasts in a densely collagenous background. Three previous case reports have described a t(2;11)(q31;q12) in this entity. Herein, we report a case of collagenous fibroma of deep soft tissue with t(11;17)(q12;p11.2). The breakpoint at chromosome 11q12 appears to be pathogenetic in this rare neoplasm.

Mineralized fibroma of the tendon sheath presenting as a bursitis

We report on the clinical, imaging-including ultrasound, computed tomography, and magnetic resonance imaging-and histological features of a fibroma of the tendon sheath with mineralized chondroid and osseous metaplasia, presenting as a semimembranosus bursitis. The anatomical characteristics of the semimembranosus bursa are demonstrated by dissection in a cadaveric specimen and correlated with the imaging findings in our patient.

Pathologic and MR Imaging Features of Benign Fibrous Soft-Tissue Tumors in Adults

Benign fibrous (fibroblastic or myofibroblastic) soft-tissue tumors are a heterogeneous group of fibrous lesions with widely varied anatomic locations, biologic behavior, and pathologic features. The four broad categories of fibrous proliferation are benign fibrous proliferations, fibromatoses, fibrosarcomas, and fibrous proliferations of infancy and childhood. The first two categories include nonaggressive fibroblastic lesions such as nodular fasciitis, as well as fibromatoses that demonstrate more aggressive biologic behavior (eg, desmoid tumors). In adults, fibrous tumors are among the most common soft-tissue lesions encountered in clinical practice. MR imaging can be useful for defining the intrinsic signal characteristics, size, and compartmental extension of these lesions. Histologic features of the tumor also may be depicted on T2-weighted MR images. Hypocellular fibrous tumors with dense collagenous components tend to have lower signal intensity on T2-weighted images than do lesions that are more cellular or that contain greater amounts of extracellular myxoid matrix. When interpreting MR images of soft-tissue masses in adults, radiologists should be aware of the clinical behavior, common sites of occurrence, and histopathologic and imaging features of the common benign fibrous soft-tissue tumors.

Intra-articular fibroma of tendon sheath of the shoulder joint: synovial fibroma

The case of a 30-year-old woman with multiple loose bodies in the shoulder joint is presented. The patient complained of discomfort of her right shoulder. Conventional radiographs failed to reveal any abnormality of the shoulder. On MRI numerous loose bodies were detected that resembled synovial chondromatosis. Histologically, the loose bodies were composed of a benign fibroblastic lesion with diagnostic features of fibroma of tendon sheath, each surfaced by synoviocytes. The clinicopathologic features of intra-articular fibroma of tendon sheath are reviewed. We propose using the term "synovial fibroma" for tumors with histopathologic features of fibroma of tendon sheath arising in the synovium of joints.

Fibrous Hamartoma of Infancy: A Case Report With Associated Cytogenetic Findings

A 2-month-old male infant presented with a subcutaneous mass on the left middle finger; the mass had been present since birth. This was treated with local excision, and there has been no recurrence. Histology revealed the typical features of a fibrous hamartoma. Cytogenetic studies revealed a reciprocal translocation, t(2;3)(q31;q21), as the sole abnormality. To our knowledge, this is the first report of the cytogenetic findings in fibrous hamartoma, and it suggests that this lesion represents a benign neoplasm.

Desmoplastic fibroblastoma: a light and ultrastructural description of two cases

The authors report 2 cases of collagenous fibroma in which ultrastructural analysis revealed the presence of fibronexus junctions, markers of myofibroblastic differentiation, never described in this rare lesion before. The tumors occurred in the trapezius muscle and in the right arms of a 41 -year-old and a 25-year-old man. They were both intramuscular and showed sharp edges. Grossly, the excised masses were whitish and firm. Microscopically, they were both composed of stellate or spindle-shaped cells separated by a collagenous hypovascular and focally myxoid stroma. Mitotic figures and necrotic areas were not identified. Immunohistochemistry showed positivity for vimentin and focal positivity for smooth and human muscle actin, and flow cytometry showed the tumoral cells to be diploid.

Translocation (2;11)(q31;q12) is recurrent in collagenous fibroma (desmoplastic fibroblastoma)

Collagenous fibroma (desmoplastic fibroblastoma) is a rare, benign tumor composed of spindle and stellate-shaped fibroblasts and myofibroblasts in a densely collagenous background. A t(2;11)(q31;q12) has been reported in one case of collagenous fibroma and a rearrangement of the 11q12 breakpoint in a second case. In the present study, we detected a t(2;11) identical to that previously described in a collagenous fibroma arising in the supraclavicular fossa of a 55-year-old man. This finding confirms the nonrandom association of t(2;11)(q31;q12) with collagenous fibroma.

Collagen-rich tumors of soft tissues: an overview

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

Diagnosis of soft tissue tumors by fine-needle aspiration with combined cytopathology and ancillary techniques

The diagnosis of mesenchymal neoplasm by fine-needle aspiration biopsy (FNAB) has presented a diagnostic challenge. Most reports claim an accuracy approaching 95%, but while they distinguish benign and malignant lesions, the most problematic group, the intermediary malignant group, is omitted. The purpose of this study was to determine whether rapid cytologic diagnosis of soft-tissue tumors could guide surgeons in therapeutic decisions without the need for a tissue biopsy. Ninety-four FNA cytologic specimens were examined by the National Soft Tissue Consortium of Hungary and compared with the corresponding histology. Ordinary lipomas were excluded. Morphologic evaluation was supplemented by ancillary techniques such as fluorescence in situ hybridization (FISH), DNA cytometry, and immunocytochemistry. From a practical clinicopathological point of view, the cases were grouped in the following categories: 1) tumors with definitive diagnosis: a) high-grade malignant neoplasms (high-grade sarcomas, metastatic carcinomas, lymphoma), b) tumors with precise histogenetic origin by cytogenetics, c) benign tumors; 2) tumors of questionable nature. In the first group there were 74 tumors: 22 high-grade sarcomas, six metastatic carcinomas, one malignant lymphoma, 16 malignant tumors in which the precise histogenetic origin could be established by cytogenetic studies, and 29 benign soft-tissue tumors other than lipomas. In the second group there were 20 tumors comprising benign and malignant soft tissue tumors of low grade, wherein the precise nature of the neoplasm could not be established with confidence on cytologic study, even using ancillary techniques. FNAB of soft-tissue tumors combined with ancillary techniques should be considered a viable diagnostic technique for therapeutic protocols. Although the second group is fairly large, we have reliable, well-characterized categories which provide great freedom for preoperative and surgical treatment, thus providing the best chance for healing.

Genetic and molecular abnormalities in tumors of the bone and soft tissues

BACKGROUND

Malignant transformation requires the accumulation of multiple genetic alterations such as chromosomal abnormalities, oncogene activation, loss of tumor suppressor genes, or abnormalities in genes that control DNA repair and genomic instability. Sarcomas are a heterogeneous group of malignant mesenchymal tumors of difficult histologic classification and strong genetic predisposition. This article provides a comprehensive review of the cytogenetic abnormalities observed in bone and soft-tissue tumors, emphasizing known downstream molecular changes that may play a role in oncogenesis.

METHODS

The database of the National Library of Medicine was searched for literature relating to genetic and molecular mechanisms in sarcomas in general and in each of the main tumor entities.

RESULTS

Recent techniques in chromosome analysis and molecular cytogenetics have improved our ability to characterize genetic changes in mesenchymal tumors. Some changes are so characteristic as to be virtually pathognomonic of particular histologic types, while others are complex, difficult to characterize, and of unknown relevance to pathogenesis. The implications to the cell of some of these abnormalities are now being recognized.

CONCLUSIONS

The study of sarcomas will benefit from the information derived from genetic studies and translational research. The human genome project and new methodologies, such as computer-based DNA microarray, may help in the histogenetic classification of sarcomas and in the identification of molecular targets for therapy.