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.

Three cases of collagenous fibroma with rim enhancement on postcontrast T1-weighted images with fat suppression

Collagenous fibroma, also known as desmoplastic fibroblastoma, is a benign fibrous soft tissue tumor showing gradual growth, commonly without aggressive local infiltration. Today, 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. We report MR imaging findings of three collagenous fibromas in correlation with their histopathology. The characteristic rim enhancement on post-contrast T1-weighted images with fat suppression was present in all three cases, and we consider this to represent the difference in vascularity between the outer capsule-like fibrous tissue and the inside of the tumor.

Desmoplastic fibroblastoma (collagenous fibroma): a case identified in the buccal mucosa

Desmoplastic fibroblastoma is a rare, benign, soft tissue tumor affecting mainly the subcutaneous and muscle tissue. Only five cases identified in the oral cavity have been reported in prior literature. This article presents a case report of a 56-year-old man, with no previous history of trauma, who presented a slow-growing mass in the buccal mucosa. Histopathology and immunohistochemistry staining studies were performed, and a diagnosis of the desmoplastic fibroblastoma was made. The patient has been disease-free for one year.

Desmoplastic fibroma of the mandible

We report the imaging findings of a desmoplastic fibroma (DF) of the mandible in a 3 years old girl. DF of bone is a rare, no-metastasizing but locally aggressive tumor. Hypercellularity, nuclear pleomorphism, mitotic activity, and traces of odontogenic epithelium and bony tissue are absent. US exam showed a highly vascular and well delimited mass, with no necrotic/hemorrhagic areas. It appeared as a well-defined osteolytic region in RX and a multiloculated, hypodense mass, with no periosteal reaction signs, in CT scans. MRI showed hypointensity in T1w TSE sequence and hyperintensity both in T1w TSE SPIR and T2w ones with no restriction of the "apparent diffusion coefficient" (ADC). In conclusion, remaining histology the gold standard for the DF diagnosis, imaging features may strongly suggest it.

[Mandibular desmoplastic fibroma: diagnosis and therapeutics difficulties]

INTRODUCTION

The desmoplastic fibroma is a rare bone tumor, characterized by aggressive local infiltration, with frequent recurrence. The most common site is the mandible. Radioclinical signs are not specific and the histological diagnosis may be difficult.

CASE

A 16 year-old male patient consulted for a painless and hard left mandibular swelling, without inferior alveolar nerve disorders. The tumor extended from tooth 31 to tooth 35, the mucosa was healthy. The panoramic view showed a multilocular osteolytic lesion with dental root resorption. CT scan showed expansion of bony cortex with rupture of the outer cortical. The biopsy indicated a desmoplastic fibroma or a fibrosarcoma. A second histological analysis combined with an immuno-histochemical study proved the diagnosis of desmoplastic fibroma.

DISCUSSION

The desmoplastic fibroma has a polymorphous symptomatology. Radiological signs are unspecific. Anatomopathology combined with immuno-histochemistry can prove the diagnosis and guide the treatment.

Desmoplastic fibroma of the anterior mandible. Case report and review of literature

Desmoplastic fibroma is a rare and locally aggressive lesion that affects the long bone and the jaw bones. Mandibular bone involvement has been mostly reported in the posterior segment; anterior region presentation is rare. This case report highlights the diagnosis, management and treatment of a midline mandibular involvement. It includes a literature review.

Infantile desmoplastic fibroma of the maxilla

BACKGROUND

Infantile desmoplastic fibromatoses are benign fibrous tissue tumours, non-metastasizing but locally aggressive and with high likelihood of recurrence. Many cases occur in young children between 18 months and 3 years and commonly present as painless mass of the submandibular region. The maxilla is rarely involved.

AIM

Through this report and a review of literature, we are going to study clinical, pathological and prognostic characteristics of this affection.

CASE REPORT

We report here a case of an aggressive desmoplastic fibroma arising in a 20-months-old infant originating in the left anterior maxillary wall. Clinical examination of the face revealed a non tender, firm, expansion of the left maxilla of 2.5 cm of diameter. The diagnosis of DF of the maxilla was made on the basis of histological features on biopsy specimen. No other location of the fibromatosis was found. The child had a favourable course.

CONCLUSION

DF is an intraosseous, non metastasizing and locally aggressive fibrous tumour. Although its benignity, it could engage vital prognosis since it can extend into vital organs.

[Desmoplastic small round-cell tumor of the paratesticular region: a case report and review of the literature]

OBJECTIVE

To investigate the clinical and pathological features of paratesticular desmoplastic small round cell tumor (DSRCT), and to improve the diagnosis and treatment of the disease.

METHODS

One case of paratesticular DSRCT was studied retrospectively and a considerable amount of related literature from Medline and Chinese journals reviewed. The patient was a 27-year-old man presenting with a painless testicular mass in the left hemiscrotum. On physical examination, a cystic mass was palpable while the testis was not in the left hemiscrotum.

RESULTS

During the operation the paratesticular area was found full of multiple nodular tumor masses of various sizes ranging from 0.5 cm to 1.5 cm in diameter. Pathological examination showed the characteristic histological pattern of nests of small undifferentiated cells embedded in a dense fibrous stroma. The tumor presented an immunohistochemical feature of epithelial, mesenchymal as well as neural multidirectional differentiation. Following testicular tumor orchiectomy, chemotherapy was performed with DDP, VP16, ifosfamide and EPI. Three years follow-up found no tumor recurrence.

CONCLUSION

Desmoplastic small round cell tumor has a specific clinicopathologic stigmata, usually occurring in young males, for which surgical resection with chemotherapy is the treatment of choice. DSRCT located in the paratesticular region may have a better prognosis than its more frequently abdominal counterpart.

[Imaging features and differentiated diagnosis of desmoplastic fibroma of the jaw bones]

PURPOSE

To investigate the imaging feature of desmoplastic fibroma (DF) of the jaw bones.

METHODS

The records including diagnostic radiograph images of 8 patients were retrospectively analyzed. The age of the 8 patients ranged from 2 years to 70 years (means,28 years). The numbers of males and females were 3 and 5 respectively. Of 8 patients, 4 had local recurrence, which occurred 1 year after curettage.

RESULTS

On conventional radiographs, the lesion was presented as a purely lytic tumor that did not contain any mineralized matrix. The zone of transition between tumor and normal bone was typically narrow and well defined but not sclerotic. Bone expansion in DF had an eccentric (n=3) and lace-like, reticular pattern (n=3). On CT scan, increased bone marrow density (n=3), a homogeneous soft-tissue density mass displaced adjacent muscle with lingual cortex eroded (n=3) were noted. On MRI, the lesion was displayed as large bony destruction area, with homogeneous hypointensity on T1-weighted images, non-homogenous hyperintensity on T2-weighted and did not enhance after Gd-DTPA administration. Images with Choline peek (Cho, at 3.2 ppm) was displayed at TE of 144 ms( PRESS, single voxel).Six mandibular cases and 2 maxillary tumors were located posteriorly.

CONCLUSIONS

Recognition of DF is important because DF is more aggressive than other benign fibrous lesions, necessitating a wide surgical and careful long-term follow-up for local recurrence.

[Desmoplastic fibroma of bone: a report of two cases]

Desmoplastic fibroma is a rare bone tumor with benign, locally aggressive, lytic behavior. Histologically, it is very similar to the more common and better known desmoid tumor. It can occur at any site in the skeleton but is most common in the mandible or in the long bones. We present two cases; the tumor was located in the proximal tip of the fibula in one case and in the proximal tip of the femur in the other. We describe the appearance of these lesions on CT and MRI. In both cases, the lesions were lytic, expansive, with a trabeculated appearance and internal septa, and without mineralized osseous matrix. At MRI, one of the tumors was very heterogeneous, with two differentiated areas on T2-weighted sequences: the upper zone was hypointense and the lower zone showed intermediate signal intensity. We also describe the behavior of the tumor after the administration of intravenous Gadolinium: the upper zone showed no significant enhancement and the lower showed significant enhancement in the early phase.

Le fibrome desmoplastique ou fibrome desmoïde osseux

Desmoplastic fibroma or desmoid bone tumor is a rare tumor described for the first time by Jaffe in 1958. It accounts for 0.1 to 0.3% of all benign bone tumors. To date, about 150 cases involving the locomotor system have been reported. Histology is required for certain diagnosis of desmoplastic fibroma. The tumor is composed of sparse fibroblasts in a rich background of collagen fibers, a histological presentation exactly the same as soft tissue desmoid fibroma. We report two new cases of desmoplastic fibroma of the locomotor system. The observations illustrate the radiological diagnosis. MRI was used to search for local extension in bone or soft tissues. Biopsy is necessary to confirm the diagnosis. The histological presentation may be difficult to recognized and distinguish from low grade fibrosarcoma. After treatment, the rate of local recurrence is high in the event of partial resection. Surgery is the optimal treatment, with tumor resection as wide as possible depending on the localization.

Desmoplastic fibroma of the pediatric skull. Report of three cases

Desmoplastic fibromas are rare bone tumors that have been reported in the adult skull but rarely in that of children. Although desmoplastic fibromas of the pediatric skull are uncommon, their similarity to benign skull lesions and their locally aggressive nature make them an important part of the differential diagnosis. Local recurrence is common after curettage alone but complete resection appears to be curative. Close follow up of incompletely resected lesions is essential. The authors detail three cases of pediatric desmoplastic fibromas of the skull and discuss diagnosis and treatment.

Desmoplastic fibroma of the mandible in an infant

We report the CT and MR imaging findings of a case of a desmoplastic fibroma of the mandible in a 6-month-old girl who presented with a rapidly enlarging facial mass and who represents one of the youngest reported children with this rare tumor. Although imaging is non-specific and these lesions are best distinguished histologically, the desmoplastic fibroma should be considered when there is an occurrence of any bubbly or cystic expansile mandibular lesion presenting in childhood.

Desmoplastic fibroma of the cervical spine

There have been only a few cases of desmoplastic fibroma of the spine in the literature and only one of them was purely located on the cervical spine. We report a new patient with the diagnosis of desmoplastic fibroma of the fourth cervical spine. The patient had the complaints of left arm and neck pain. After his radiological evaluation, a mass lesion was found on the left lamina of the fourth cervical spine. Surgical treatment was performed, and the histopathological examination revealed the diagnosis of desmoplastic fibroma. Patients with desmoplastic fibroma of the cervical spine may present with the arm and neck pain mimicking cervical disc disease. Higher index of suspicion by the clinicians must be practiced to make the appropriate diagnosis. Successful surgical outcome may be achieved in these patients.

[Benign desmoplastic fibroblastoma of the lower leg. A rare case]

Desmoplastic fibroblastoma ("collagenous fibroma") is a benign fibrous soft tissue tumor. We report a rare case of a "collagenous fibroma" located in the proximal lower leg in 56-year-old man. The clinical, radiological, and pathological-morphological findings are documented. The operative treatment was performed according to general principles of surgical management of benign soft tissue tumors.

Desmoplastic fibroma of bone: case report

Desmoplastic fibroma of bone is an exceedingly rare tumor that was first described by Jaffe in 1958 [1]. It has a high incidence of local recurrence after surgical resection. It is usually seen in young patients and involves mandible and long bones. It has histological resemblance to the desmoid tumor of the abdominal wall. We report a surgically proven case of desmoplastic fibroma of bone with local aggressiveness and recurrence during follow-up. The radiograph, CT imaging features, radiological and pathological differential diagnosis of the case are described, and literature is briefly reviewed.

Three-level en bloc spondylectomy for desmoplastic fibroma of the thoracic spine: a case report

STUDY DESIGN

A case of desmoplastic fibroma of the thoracic spine treated by a three-level en bloc spondylectomy is reported.

OBJECTIVES

To present a rare case of desmoplastic fibroma of the spine, and to emphasize the importance of at least a marginal resection of this tumor entity.

SUMMARY OF BACKGROUND DATA

Desmoplastic fibroma is a rare tumor, with the literature reporting approximately 220 cases of the disorder in patients younger than 30 years of age. This disorder has a predilection for the mandible and the meta-diaphyses of long bones. A location of desmoplastic fibroma in the spine has been reported in only a few cases. Desmoplastic fibroma has a high tendency of local recurrence, especially after intralesional resection.

METHODS

The reported case is that of a 14-year-old girl with a desmoplastic fibroma of the 9th, 10th, and 11th vertebrae. After confirmation of the diagnosis by CT-guided biopsy, a three-level en bloc spondylectomy with marginal resection of the desmoplastic fibroma was performed from the posterior approach. Stabilization was achieved with a multilevel pedicle screw instrumentation, and an autologous fibula was used for reconstruction.

RESULTS

At this writing, 31 months after surgery, the girl has no evidence of recurrence and is pain free.

CONCLUSIONS

Wide resection of tumors located in the spine actually is impossible to achieve because of the anatomic relations to the spinal cord, the major vessels, and the lung. As in the current case, a marginal resection is the maximal one to be achieved. Three of seven cases (43%) of desmoplastic fibroma in the spine treated by intralesional resection resulted in a local recurrence. These data clarify the importance of at least marginal resection of desmoplastic fibroma, if this is anatomically and technically possible. A local recurrence of desmoplastic fibroma in the spine can be impossible to treat surgically with a curative intention without a significant loss of function.

Desmoplastic fibroma of the cranium: case report and review of the literature

OBJECTIVE AND IMPORTANCE

Desmoplastic fibroma is a benign bone tumor that can be locally aggressive. It usually occurs in the long bones and mandible. We report on a patient with a desmoplastic fibroma arising in the temporal bone and review previously published cases of desmoplastic fibroma originating within the cranium.

CLINICAL PRESENTATION

A 43-year-old woman presented with a 12-year history of progressively worsening head asymmetry. Magnetic resonance imaging and computed tomography demonstrated a mass originating from the bone and involving the adjacent soft tissues.

INTERVENTION

A temporal parietal craniectomy was performed with excision of a large tumor involving the bone. An acrylic cranioplasty was used to replace the bone. Pathological examination of the lesion identified desmoplastic fibroma of the cranium. After surgery, the patient's cranial asymmetry was corrected.

CONCLUSION

Desmoplastic fibroma of the cranium is rare. Surgical resection is the treatment of choice.

Desmoid tumor of bone with enchondromatous nodules, mistaken for chondrosarcoma

Desmoid tumor of bone, also termed desmoplastic fibroma or aggressive fibromatosis, is a rare, locally aggressive fibroblastic tumor. We present a 16-year-old male with a huge desmoid tumor involving the iliac wing. It was associated with enchondromatous nodules mimicking malignancy. The tumor in this patient was mistaken for chondrosarcoma and hemipelvectomy was performed. To our knowledge, such a case has not previously been documented fully in the English literature. The radiographic and pathologic findings and a possible mechanism of enchondromatous nodule formation in fibrous bone tumors are discussed.

Low-grade fibrosarcoma of the proximal humerus

We present the clinical, radiographical and pathological features of low-grade fibrosarcoma of the left proximal humerus in a 23-year-old man in whom it was necessary to distinguish the tumor from desmoplastic fibroma, malignant fibrous histiocytoma and intramedullary well-differentiated osteosarcoma. The patient presented with a 10-day history of pain in his left upper arm sustained when trying to break his fall with his left hand when slipping in the street. Plain radiography revealed an expanding multilobular osteolytic lesion from the proximal metaphysis to the diaphysis of his left humerus, accompanied by a pathological fracture at the distal portion of the lesion. Open biopsy of the lesion was performed twice; however, a conclusive diagnosis could not be obtained. The patient underwent wide excision and prosthetic replacement of the left proximal humerus. Histologically, the resected tumor was composed of both cellular areas and hypocellular areas. Cellular areas revealed a proliferation of bundles of uniform fibroblastic spindle-shaped cells with minimal cellular atypia, mixed with abundant intercellular collagenization. Mitotic figures were occasionally seen. Hypocellular areas showed myxoid features with loose bundles of collagen fibers. The patient demonstrates no evidence of disease 42 months after surgery. It is important to detect the scant atypical cells for the differential diagnosis of low-grade fibrosarcoma and desmoplastic fibroma of bone.

CT and MR imaging of desmoplastic fibroblastoma

Desmoplastic fibroblastoma (collagenous fibroma) developing as a slowly enlarging lower abdominal mass is described. The lesion had inhomogeneous low signal intensity (SI) on T1-weighted images, and mixed SI as low SI within high SI on T2-weighted images. On post-contrast T1-weighted images, the mass showed inhomogeneous enhancement. Histologically, the areas showing low SI on both post-contrast T1- and T2-weighted images consisted of dense collagenous components and reduced cellularity compared with the areas showing high SI on them.

Desmoplastic fibroma in the thoracic spine: an unusual localization of a rare primary bone tumor

A case of an intraspinal growing desmoplastic fibroma of the thoracic spine (T9-T11) is reported. Desmoplastic fibroma is a rare tumor of connective tissue that shows a locally infiltrative and destructive growth. An affection of the thoracic spine is an extremely rare manifestation. Preoperative CT documents the extent of osseous destruction and tumor associated cortical erosion. In central tumor areas an inhomogeneous, intermediate to low signal is demonstrated by MRI using T1- and T2-weighted spin-echo and turbo-spin-echo sequences. Contrast-enhanced MRI shows marked enhancement in peripheral areas depicting the extraosseous and intramedullary extension.

[Desmoplastic fibroma of the fibula. A difficult clinical, radiological and histological diagnosis]

Desmoplastic fibroma of bone is a rare benign tumor that is made up of wavy fibroblasts and abundant collagenous tissue. The case of a 18-year-old patient is presented with a two months history of weightbearing pain in the left knee. Neither native x-ray, CT nor MRI could detect the kind of tumor. The histological findings lead finally to the diagnosis of a desmoplastic fibroma. Wide resection prevented recurrence of the tumor for 8 1/2 years until now. Considering the semi-malignant character of the desmoplastic fibroma and the recurrence rate marginal or wide resection for the primary treatment is recommended. The superior imaging quality of MRI facilitates preoperative planning.

Primary musculoskeletal tumors of fibrous origin

Tumors of fibrous origin include fibrous dysplasia (FD), fibroxanthoma (nonossifying fibroma), cortical desmoid, desmoplastic fibroma, fibrosarcoma, and malignant fibrous histiocytosis (MFH). Benign fibrous lesions (FD, fibroxanthoma, and cortical desmoid) frequently demonstrate pathognomonic radiologic characteristics obviating the need for biopsy. Indeed, biopsy of these lesions can occasionally lead to confusion with more aggressive lesions. Desmoplastic fibroma and the malignant fibrous lesions (fibrosarcoma and MFH) often reveal nonspecific imaging features of a solitary nonmineralized lesion with aggressive characteristics. However, imaging is important as with other neoplasms in delineating the extent of involvement for staging purposes. This article reviews the spectrum of clinical characteristics, pathology, imaging appearances, treatment, and prognosis of lesions of fibrous origin in bone.

Selected case from the Arkadi M. Rywlin International Pathology Slide Seminar: desmoplastic fibroblastoma (collagenous fibroma)

Desmoplastic fibroblastoma (collagenous fibroma) is a rare and recently described benign soft tissue tumor. It is more common in men, median age is 50 years, the history is usually long, and the usual size is around 3 cm. Most lesions are subcutaneous but approximately 25% involve skeletal muscle. Histologically, they are sparsely cellular with stellate and spindle-shaped fibroblasts-myofibroblasts that are separated by a collagenous or myxocollagenous matrix. Mitoses are minimal or absent. Tumor cells are focally positive for muscle-specific and alpha smooth muscle actins, and rarely, for keratins. The S-100 is usually negative but a very few cases have been positive. It can be confused with one of the fibromatoses, myxomas of various kinds and neural tumors. It neither recurs nor metastasizes.

Desmoplastic fibroma of the temporal bone

An unusual case of a desmoplastic fibroma of the temporal bone is presented. Although classified benign, this intraosseous lesion exhibits local aggressiveness and has a high potential for recurrence. This rare condition occurs predominantly in the mandible and in the long bones and is seldom seen in the calvarium. Here we add another case to the previously described eight in the skull and this is the fourth such case reported in the temporal bone. The clinical features, radiology, histopathology and the therapeutic considerations of this lesion in a 72-year-old female are discussed. In addition, a literature review of all the cases affecting the skull bones is presented.

Desmoplastic fibroma of bone: MRI features

Desmoplastic fibroma of bone is a very rare benign tumor, which may be locally aggressive. In contrast to the well-documented radiological appearance, the literature on MR imaging features of this tumor is scarce. The MR imaging characteristics in our case are compared to those previously reported. Although there is a considerable overlap in the MR imaging features with other bone tumors, an interesting MR feature of desmoplastic fibroma is the presence of low to intermediate signal intensity foci on T2-weighted images, which radiographically does not correspond to calcifications. This feature may help narrow the differential diagnosis.

MR findings of desmoplastic fibroma of the spine. A case report

We report on the MR imaging findings in a case of spinal desmoplastic fibroma (DF). DF of the bone is a rare, locally aggressive tumor. It is commonly located in long bones, pelvis or mandible. DF involving the spine is extremely rare and difficult to distinguish from other bony lesions such as giant cell tumor, chordoma and fibrous dysplasia of the spine. This case of DF of the spine showed MR findings similar to those of DF arising in the metaphysis of a long bone.

Odontogenic fibroma

The odontogenic fibroma is a rare tumor that has generated controversy, perhaps disproportionately to its importance in the family of odontogenic tumors. The clinical and radiographic features are well documented but the histologic aspects have generated controversy. The behavior is benign, and published accounts indicate a low recurrence rate following treatment by curettage. The tumor recognized by the World Health Organization (WHO) is the legitimate odontogenic fibroma. Histologic variants include the granular cell type and the hybrid odontogenic fibroma giant cell-like tumor. Although the extraosseous "peripheral" odontogenic fibroma presents as a gingival enlargement clinically indistinguishable from other gingival lesions, its histomorphology is similar to the central tumor. A normal dental follicle around the crown of an unerupted tooth may histologically mimic the odontogenic fibroma and other odontogenic tumors.

Synovial desmoplastic fibroblastoma of hip joint with bone erosion

A 78-year-old woman presented with pain at the left hip. Initial radiographs showed minimal age-related changes. Over the next 2 years she developed large erosions in the left femoral neck and proceeded to hip replacement. Histological examination showed bland spindle cells in a loose and hyalinised collagenous stroma considered to represent a desmoplastic fibroblastoma (collagenous fibroma). This is the first reported case of synovial desmoplastic fibroblastoma.

Desmoplastic fibroma of the zygoma

Desmoplastic fibroma is an exceedingly rare primary bone tumor. Previous reports have not included the presentation of this tumor associated with the zygoma. This report describes the unusual presentation and surgical management of a desmoplastic fibroma of the zygoma.

Desmoplastic fibroma of the mandible in a child: report of a case

A 6-year-old girl was seen with a history of progressive trismus and expansion of the right mandible over a 9-month period. Desmoplastic fibroma was diagnosed on biopsy. This report reviews the diagnostic criteria and surgical management of this uncommon primary bone tumor of the maxillofacial region.

Desmoplastic fibroma of the bone. A report of two patients, review of the literature, and therapeutic implications

BACKGROUND

Desmoplastic fibroma (DF) is an extremely rare bone tumor. The recommendations for therapy are often based on limited personal experience, and the rate of local recurrence in the published cases is very high. Therefore, an analysis of treatment results of published cases was performed. Furthermore, DNA analysis of the tumors from two patients was also performed.

METHODS

The clinical, radiologic, and histologic data of two patients with DF of the long bones are presented. DNA flow cytometry was performed on both DFs, three cases of abdominal fibromatosis, and three cases of extraabdominal fibromatosis. One hundred eighty-nine patients analyzed in the literature and our own 2 patients were evaluated with regard to epidemiologic, clinical, and histologic data, with particular emphasis on treatment results.

RESULTS

DNA analysis of the locally infiltrating tumors revealed indices of proliferation between 21.5% and 24%, noticeably elevated values in comparison with extraosseous desmoid tumors (8.04%). Magnetic resonance imaging (MRI) was most valuable for imaging the intraosseous and extraosseous extent of DF. The evaluation of 191 patients (189 from the literature, 2 of the authors) showed the numbers of males and females to be equivalent, with a mean age of 23 years. DF has been reported in almost all bones, with a tendency to occur in the mandible and the long bones. Approximately 12% of patients presented with a pathologic fracture (20 of 161 patients). Infiltrative growth in the soft tissue was documented in 48% of patients. Three patients developed metastases after local recurrence. Analyzing the treatment results, the authors found a recurrence rate of 55-72% after nonresection procedures, and 17% after resection. No recurrences are reported after resection with wide surgical margins. The recurrence rate of tumors of the extremities was 55%, and 25% of these patients eventually required an amputation.

CONCLUSIONS

Considering the "semimalignant" character of this entity and the poor treatment results in patients with recurrent tumors, marginal or wide resection for primary treatment is recommended. The superior imaging quality of MRI greatly facilitates preoperative planning.

Case report 847. Juxtacortical aggressive fibromatosis (desmoplastic fibroma) of the forearm

A case has been presented of a 14-year-old male patient who developed a fusiform mass on the volar aspect of his left forearm following two fractures. Microscopic features and plain radiography, CT, and MRI appearance of juxtacortical aggressive fibromatosis are discussed.

Extra-abdominal desmoid fibromatosis

Desmoid fibromatosis cannot be considered a biologically benign or innocuous lesion. In the head and neck it may be intraosseous (desmoplastic fibroma) or, more often, in soft tissues, with the highest incidence in the supraclavicular region of the neck. High recurrence and persistence rates, 50% or more, accompany intralesional or marginal excision. Keloids and proliferative scars, while stubborn in their resolution and potentially disfiguring, are reactive proliferative disorders of fibroblastic and myofibroblastic tissues.