Recurrent FOSL1 rearrangements in desmoplastic fibroblastoma.

The FOS gene family has been implicated in tumourigenesis across several tumour types, particularly mesenchymal tumours. The rare fibrous tumour desmoplastic fibroblastoma is characterised by overexpression of FOSL1. However, previous studies using cytogenetic and molecular techniques did not identify an underlying somatic change involving the FOSL1 gene to explain this finding. Prompted by an unusual index case, we report the discovery of a novel FOSL1 rearrangement in desmoplastic fibroblastoma using whole-genome and targeted RNA sequencing. We investigated 15 desmoplastic fibroblastomas and 15 fibromas of tendon sheath using immunohistochemistry, in situ hybridisation and targeted RNA sequencing. Rearrangements in FOSL1 and FOS were identified in 10/15 and 2/15 desmoplastic fibroblastomas respectively, which mirrors the pattern of FOS rearrangements observed in benign bone and vascular tumours. Fibroma of tendon sheath, which shares histological features with desmoplastic fibroblastoma, harboured USP6 rearrangements in 9/15 cases and did not demonstrate rearrangements in any of the four FOS genes. The overall concordance between FOSL1 immunohistochemistry and RNA sequencing results was 90%. These findings illustrate that FOSL1 and FOS rearrangements are a recurrent event in desmoplastic fibroblastoma, establishing this finding as a useful diagnostic adjunct and expanding the spectrum of tumours driven by FOS gene family alterations. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Superficial desmoplastic fibroblastoma (collagenous fibroma): Clinicopathologic study of 11 cases.

BACKGROUND: Desmoplastic fibroblastoma (collagenous fibroma) is a rare soft tissue tumor that usually arises in the subcutis or skeletal muscle. Cases superficial to fascia are unusual and can cause diagnostic difficulty. We present 11 cases of superficial desmoplastic fibroblastoma involving a wide anatomic distribution. METHODS: Archives were searched using the term "desmoplastic fibroblastoma" over a 10-year period (2012-2022). Cases superficial to fascia were retrieved, and available clinicopathologic features were recorded. Only cases involving the dermis were included. RESULTS: Eleven cases were identified, all of which were received in consultation. Tumors involved the head and neck (2), lower extremity (2), back (2), foot (1), shoulder (1), axilla (1), hand (1), and breast (1). Each consisted of a hypocellular proliferation of bland stellate to spindled fibroblasts set in a collagenous to focally myxoid stroma. The immunohistochemical stains available for review demonstrated SMA positivity (4/7) and negative immunoreactivity for CD34 (0/6), EMA (0/3), desmin (0/3), and S100 (0/7). CONCLUSIONS: Desmoplastic fibroblastoma may present superficially in the dermis to subcutis, posing a potential source of diagnostic difficulty. Recognition of the characteristic histopathologic features of desmoplastic fibroblastoma with judicial use of immunohistochemical stains should allow for accurate diagnosis.

Desmoplastic Fibroblastoma: An Uncommon Tumor With a Relatively Characteristic MRI Appearance.

OBJECTIVE. We undertook this study to determine the radiologic features of desmo-plastic fibroblastoma. MATERIALS AND METHODS. We reviewed available radiologic images for 29 pathologically confirmed desmoplastic fibroblastomas, including images from MRI, radiography, ultrasound (US), and CT. RESULTS. The patient population included 14 women and 15 men (mean age, 60 years; range, 23-96 years). Typically, lesions were oval or lobulated and relatively small (mean, 5.6 cm). In 14 of the 22 cases that included patient histories, lesions had grown slowly, with two eventually causing pain. The remaining eight were discovered incidentally. All lesions involved or were below the deep fascia. Lesions were well-defined and associated with muscle (45%), deep fascia (28%), joint (21%), or tendon (7%). MR images were available in 26 cases; 14 included unenhanced and contrast-enhanced studies. On MRI imaging all lesions were well-defined and adjacent to dense connective tissue. On T1-weighted images, lesions showed varying amounts of low and intermediate signal intensity similar to that of tendon and skeletal muscle, respectively. On fluid-sensitive images, lesions were more heterogeneous, generally showing a wider spectrum of decreased to intermediate signal intensity. On contrast-enhanced MR images, enhancement was characteristically peripheral and septal with patchy areas of homogeneity. In the 10 cases with radiographs, images showed negative findings or a nonmineralized mass. The 10 available ultrasound studies showed mixed echogenicity. In eight patients, unenhanced CT showed lesions having attenuation similar to that of skeletal muscle. CONCLUSION. Desmoplastic fibroblastoma is an uncommon neoplasm with a relatively characteristic MRI appearance.

Desmoplastic fibroblastoma mimicking tenosynovial giant cell tumor encasing a tendon of the foot.

Desmoplastic fibroblastoma is an uncommon, benign fibrous soft tissue tumor that usually occurs in the arms, shoulders, neck, hands, and feet in the fifth to seventh decades of life. In general, it is commonly located in the subcutaneous tissue and skeletal muscle. The authors report an unusual case of a desmoplastic fibroblastoma mimicking tenosynovial giant cell tumor encasing a tendon of the foot in a 72-year-old woman. Ultrasonography revealed an inhomogeneously hypoechoic lobulated soft tissue lesion completely wrapped around the extensor digitorum longus tendon. Color Doppler study revealed increased vascularity in the internal and peripheral portions of the lesion. Magnetic resonance imaging revealed a well-defined, lobulated soft tissue mass encasing the extensor digitorum longus tendon with predominantly isointense signal with some areas of hypointense signal on T1-weighted images, predominantly hyperintense signal with some areas of hypointense signal on T2-weighted images, and inhomogeneous enhancement on fat-suppressed contrast-enhanced T1-weighted images. Surgical excision was performed, and the mass was diagnosed on pathological examination as a desmoplastic fibroblastoma. There has been no previously published radiologic case of a desmoplastic fibroblastoma encasing a tendon of the foot in the literature.

Rib desmoplastic fibroblastoma: Video-assisted resection.

A 46-year-old man was referred to our department due to chronic chest pain. A computed tomography showed an exophytic image arising from 5th rib that was projected on the middle lobule. The patient underwent an exploratory videothoracoscopic because we couldn't discard lung compromise. A corneal-like lesion emerging from the inner side of the 5th rib was revealed. Complete video-assited resection was done. Histopathology examination revealed a desmoplastic fibroblastoma. To our knowledge this is the first case of desmoplastic fibroblastoma arising from a rib and the second case published in all literature of chest wall involvement.

Calcified desmoplastic fibroblastoma of the foot: imaging findings.

We report a case of desmoplastic fibroblastoma (DF) of the foot in a 65-year-old woman. The tumor presented as a slow-growing, painless mass located in the first intermetatarsal space of the right foot. Ultrasound showed a well-circumscribed hypoechoic lesion containing hyperechoic calcifications confirmed on standard radiographs. At magnetic resonance imaging (MRI), the mass appeared isointense to the muscles on T1-weighted (T1W) images, hyperintense on proton-density-weighted fat-saturated images, and presented scattered internal hypointense foci. Post-contrast T1W spectral presaturation with inversion recovery (SPIR) images showed heterogeneous, mostly peripheral, contrast enhancement. DF must be considered in the differential diagnosis of soft-tissue calcified tumors of the foot.

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.

Dermal desmoplastic fibroblastoma presenting as a large sacral mass.

Desmoplastic fibroblastoma (collagenous fibroma) is a rare and recently recognised benign tumour. Most desmoplastic fibroblastomas arise in the subcutaneous tissue or skeletal muscle. Involvement of the dermis is extremely rare. We describe an unusual case of dermal desmoplastic fibroblastoma presenting as a large sacral mass in a 16-year-old male. An awareness of this entity is necessary to avoid confusion with other benign and malignant soft tissue neoplasms.

Subcutaneous fibroblastoma resembling hemangioma: A case of benign tumor of the chest wall.

Key Clinical Message: Desmoplastic fibroma presents similar to other soft tissue tumors to such an extent that even a gold standard investigation can miss. Abstract: This is to report a mass in a 47-year-old male arising from the chest wall, which was first thought to be a hemangioma but was later diagnosed as a case of desmoplastic fibroblastoma with the help of a biopsy.

Bilateral collagenous fibroma of the hard palate: a case report and review of the literature.

BACKGROUND: Collagenous fibroma or desmoplastic fibroblastoma is a rare benign fibrous tissue tumor. It usually presents as a painless, slowly growing mass. Collagenous fibroma arises ordinarily inside the subcutaneous tissues or skeletal muscles. Histopathologically, the tumor consists of scattered stellate and spindle cells in a hypovascular collagenous stroma without atypia or infiltration. The oral cavity is a very uncommon site for desmoplastic fibroblastoma. Only 15 published articles in the literature reported the intraoral location. We present a case of collagenous fibroma with a bilateral distribution on the hard palate. This is the second case of bilateral collagenous fibroma after a previously reported one in literature; however, our case was larger, occupying almost the whole palate. We discuss the management of this rare tumor and how we can reach definite diagnosis. CASE PRESENTATION: A 37-year-old Caucasian female patient had a huge bilateral firm palatal mass that caused breathing problems. There was no history of trauma and the patient had no relevant medical history Total surgical excision under general anesthesia was carried out and histopathological examination suggested a benign mesenchymal tumor. Immunohistochemistry was necessary to confirm the tumor origin and to exclude aggressive fibromatosis. A diagnosis of bilateral collagenous fibroma was reached. Six months after surgery, there was no recurring lesion and the patient's health was good. CONCLUSIONS: Collagenous fibroma is a benign fibrous tissue tumor of unknown cause that is treated with simple excision. The prognosis is good with no recurrence. Reaching an accurate diagnosis is mandatory to avoid aggressive treatment since collagenous fibroma may be misdiagnosed as aggressive fibromatosis in case of massive size. Clinicians and pathologists should be aware of this unusual tumor for conservative management without side effects.

A Rare Case of Intraperitoneal Desmoplastic Fibroblastoma.

Desmoplastic fibroblastoma is a benign soft tissue tumor of indolent nature. It is more prevalent in males in their fourth to sixth decades of life and typically presents in the upper extremities, feet, and back. Other, uncommon locations have been reported as well, including the oral cavity and retroperitoneum. Histological examination demonstrates bland spindle cells in a dense collagenous stroma. The tumor neither recurs nor metastasizes. In this report, we discuss a case of a female patient who presented with symptoms concerning for intra-abdominal sepsis and was subsequently diagnosed with an intraperitoneal desmoplastic fibroblastoma. There is no evidence that this condition has been previously reported in the literature in the English language. The lesion was excised during laparoscopy and the patient showed no evidence of recurrence on magnetic resonance elastography (MRE) imaging 12 months later.

Desmoplastic Fibroblastoma of the Supraclavicular Region: A Rare Soft-Tissue Tumor With a Review from the Last Decade.

Desmoplastic fibroblastoma (DF) is primarily a sporadic, rare, benign, soft-tissue tumor with an excellent prognosis and no reported recurrence to date. DF presents as a painless, slow-growing mass with symptoms due to its mass effect. We report a case of a middle-aged man presenting with a right supraclavicular mass and numbness of the right arm, eventually diagnosed as DF. After confirming the diagnosis with imaging and biopsy studies, the tumor was successfully excised using a transcervical approach with no complication or recurrence detected during the 2-year follow-up after surgery. A review of the relevant literature is presented regarding the presentation, diagnosis, and outcomes of published case reports of DF coinciding with those of our discussed case. This case report adds to the pool of uncommon DF cases mainly for its unique symptoms and location. It also highlights the necessity of health education related to painless masses that might be attributed as trivial in the community.

Primary desmoplastic fibroblastoma of diaphragm.

Desmoplastic fibroblastoma is an extremely rare benign soft tissue tumor and desmoplastic fibroblastoma originating from the diaphragm has not been documented previously. In our case, we report the first primary diaphragm desmoplastic fibroblastoma.

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.

A desmoplastic fibroblastoma that developed in the anterior mediastinum: a case report.

BACKGROUND: Desmoplastic fibroblastoma (also known as collagenous fibroma) is a benign, slowly growing soft-tissue tumor. Most desmoplastic fibroblastomas develop in the limbs, neck, or trunk. A mediastinal origin is quite rare. CASE PRESENTATION: A 32-year-old Asian female was referred to us for the diagnosis and treatment of an anterior mediastinal tumor. The tumor was 80 mm in the largest diameter and was located on the pericardium. No invasion was evident. She underwent resection of the tumor via video-assisted thoracoscopic resection. The tumor was totally encapsulated, and its pedicle was on the pericardium. The resected specimen was very rigid, making it difficult to remove from the intercostal space. Histologically, the tumor was composed of a paucicellular dense collagenous tissue. Mitosis was rarely observed, and cellular atypia was not evident, suggesting that the tumor was benign. We diagnosed the tumor as a desmoplastic fibroblastoma by morphology and immunohistochemistry. CONCLUSIONS: Desmoplastic fibroblastoma of the mediastinum is an extremely rare disease. Preoperative diagnosis is difficult. Early surgical resection is suitable for diagnosis and treatment planning.

An extremely rare case of desmoplastic fibroblastoma exhibiting rapid growth in the chest wall: a case report.

BACKGROUND: Desmoplastic fibroblastoma is an uncommon, benign, fibrous tumor exhibiting infiltrative growth. Most of these tumors are small, slow-growing, and develop as subcutaneous lesions in the extremities. Cases of desmoplastic fibroblastoma in the chest wall are quite rare, and the preoperative diagnosis of such cases remains challenging as these tumors can mimic the characteristics of desmoid-type fibromatosis, which often occurs in the chest wall. We aimed to describe a rare case of desmoplastic fibroblastoma exhibiting rapid growth in the chest wall of a patient that was successfully treated with marginal excision only by diagnostic imaging before surgery. CASE PRESENTATION: A 79-year-old man was admitted to our hospital after experiencing right shoulder pain lasting for a few months. A 4 × 4 × 2 cm mass was incidentally detected at the right second rib two years prior. Chest computed tomography revealed a well-defined homogeneous mass with a muscle-like density along the right lateral chest wall, the size of which had increased to 12 × 10 × 4.5 cm in two years. Dynamic contrast-enhanced computed tomography revealed abundant vascularity at the periphery of the tumor. Magnetic resonance imaging revealed iso-intensity to muscle on T1-weighted images, slightly high intensity on T2-weighted images, and rim-like contrast enhancement at the periphery of the tumor, with uniform thickness on gadolinium-enhanced T1-weighted images with fat suppression. Rim-like contrast enhancement is an imaging feature that can distinguish cases of desmoplastic fibroblastoma from desmoid-type fibromatosis. We diagnosed the tumor as desmoplastic fibroblastoma by diagnostic imaging without tissue biopsy. Marginal excision with videoscopic assistance was performed through a small incision. The pathological diagnosis was desmoplastic fibroblastoma. The patient's postoperative course was uneventful, and his shoulder pain was relieved after the surgery. CONCLUSIONS: Desmoplastic fibroblastoma in the chest wall is extremely rare, but should be considered in the differential diagnosis when desmoid-type fibromatosis is clinically suspected. Gadolinium-enhanced magnetic resonance imaging is helpful in confirming the differential diagnosis.

A case of raised CA 19-9 in a patient with desmoplastic fibroblastoma of the upper limb.

Carbohydrate antigen 19-9 (CA 19-9) is a tumor marker widely accepted as the most useful blood test in diagnosing and monitoring pancreatic cancer. However, CA 19-9 may also be raised in other conditions such as colorectal, hepatic, lung, and ovarian carcinoma as well as benign conditions such as hepatobiliary and pulmonary diseases. CA 19-9 is rarely elevated above 200 U/ml in benign conditions with values exceeding 1000 U/ml being highly suggestive of malignancy. The mechanism of secretion in both malignant and benign conditions remains unclear. Desmoplastic fibroblastoma (DF) is a benign soft tissue tumor. CA 19-9 has not been reported in association with DF previously. We present a case of raised serum CA 19-9 in a 71-year-old male attributed solely to DF in his left cubital fossa. The patient's CA 19-9 level rose from 56 U/ml at the time of presentation to 3763.8 U/ml over a period of 9 months. Post-DF excision, the CA 19-9 level decreased to 1464 U/ml at 1 month, 162.3 U/ml at 2.5 months, and 24U/ml, within normal range, at 7 months post-surgery. CA 19-9 levels continued to remain at 24 U/ml 1.5 years post-tumor excision. The CA 19-9 level in this patient was highly elevated which is unusual in association with a benign tumor. The rate of decrease in CA 19-9 level post-excision was in keeping with that reported after pancreatic cancer resections. This is the first case of DF in association with raised CA 19-9.

Desmoplastic Fibroblastoma of the Scalp Accompanied by Severe Pain; Unusual Location and Symptom.

Desmoplastic fibroblastoma is a rare fibrous tumor that usually presents as a painless, slow-growing mass in the subcutaneous tissues and skeletal muscles. It has a wide anatomic distribution, with the most common involvement being the arm and shoulder. Here, we report a case of a tiny painful desmoplastic fibroblastoma arising on the scalp. According to a microscopic examination, this tumor was composed of spindle-shaped fibroblasts in the dense collagenous stroma. On immunohistochemical staining, tumor cells were positive for vimentin and negative for smooth muscle actin, CD34, and S100. Our case is unique in that desmoplastic fibroblastoma developed on the scalp and there was presence of pain despite its small size.

Giant calvarial desmoplastic fibroblastoma.

We describe to our knowledge the first patient with giant desmoplastic fibroblastoma of the calvarium in a 20-year-old woman whose tumor first appeared at the age of 5 years. We also discuss the histopathological differential diagnosis, management dilemmas and complications of desmoplastic fibroblastoma.

US and MRI appearance of a collagenous fibroma (desmoplastic fibroblastoma) of the shoulder.

Collagenous fibroma (desmoplastic fibroblastoma) is a recently described rare benign tumor. Since this tumor was characterized by Evans in 1995, fewer than 100 cases have been reported in English literature with the largest series published by Miettinen and Fetsch. Preoperative radiological diagnosis is important to avoid over-treatment and unnecessary extensive procedures, but is difficult because diagnostic imaging findings for collagenous fibroma have not been established. Here we report the US and MRI appearance of a lesion localized deep under the deltoid muscle in a 34-year-old woman with a palpable painless mass. Histological findings were consistent with a collagenous fibroma. As far as we know, this is the first description of US appearance of a collagenous fibroma in English literature.