Multimodality imaging features of USP6-associated neoplasms

Since the discovery of USP6 gene rearrangements in aneurysmal bone cysts nearly 20 years ago, we have come to recognize that there is a family of USP6-driven mesenchymal neoplasms with overlapping clinical, morphologic, and imaging features. This family of neoplasms now includes myositis ossificans, aneurysmal bone cyst, nodular fasciitis, fibroma of tendon sheath, fibro-osseous pseudotumor of digits, and their associated variants. While generally benign and in many cases self-limiting, these lesions may undergo rapid growth, and be confused with malignant bone and soft tissue lesions, both clinically and on imaging. The purpose of this article is to review the imaging characteristics of the spectrum of USP6-driven neoplasms, highlight key features that allow distinction from malignant bone or soft tissue lesions, and discuss the role of imaging and molecular analysis in diagnosis.

Unusual presentation of an aneurysmal bone cyst: A case report and literature review

Aneurysmal bone cysts (ABCs) are non-neoplastic primary bone tumors, typically involving the long bones and vertebrae in the first 2 decades of life. ABCs require prompt diagnosis and intervention due to their rapidly expansile nature and ability to destroy the adjacent normal bone. ABCs rarely affect the rib. We report a case of a 51-year-old female presenting with chronic dry cough and right upper back pain. A chest X-ray and computed tomography scan revealed an expansile, lytic mass affecting the posterior aspect of the third right rib. The third right rib was resected using a posterolateral, Shaw-Paulson approach. Histopathology of the resected mass confirmed the diagnosis of ABC. There were no intra- or perioperative complications, and follow-up X-ray was normal.

Diaphyseal aneurysmal bone cysts (ABCs) of long bones in extremities: Analysis of surgical management and comparison with metaphyseal lesions

INTRODUCTION

Aneurysmal bone cysts (ABCs) are benign lesions of long bone metaphysis affecting mostly medullary region in younger age below 20 years of life. These may be originated rarely either in the cortex or in the superficial regions of diaphysis. The study highlighted the differences of diaphyseal lesions from the usual metaphyseal ones in view of their clinical, radiological and biological behavior and also discussed their management in brief.

MATERIAL AND METHODS

We reviewed a total of 84 aneurysmal bone cysts over the past fourteen years (2004-2017) and evaluated their surgical outcomes retrospectively. Total ten lesions were diaphyseal cortical in location (group I), while 74 lesions were conventional metaphyseal type (group II).

RESULTS

We observed that cortical ABCs were occurred commonly in diaphysis of femur, humerus, tibia and radius while presentation was at an older age than metaphyseal type. Radiographically these were eccentric lesion and more prone for pathological fractures than conventional type. These are differentiated radiographically from other benign lesions but also mimicking malignant conditions including low grade surface osteosarcoma and telangiectatic osteosarcoma while resemble similar to these on histopathological examination (HPE).

CONCLUSION

Biological behavior of cortical lesions does not differ significantly than conventional type but these are more prone for pathological fractures so these eccentric cortical ABC lesions should be treated with adequate internal fixation along with curettage and bone grafting. Although incidence of cortical or surface variety of ABCs is rare but surgeons might evaluate its severity in view of aggressive benign or malignant lesions of diaphysis.

Rare aneurysmal bone cysts: multifocal, extraosseous, and surface variants

Multifocal, extraosseous, and surface aneurysmal bone cysts are rare variants of the primary lesions. The clinicopathological features are similar, and the optimal treatment is surgical. Although local recurrences may occur, the prognosis is excellent. This review article introduces the readers to a rare diagnosis which they may have been previously unfamiliar with, presents the clinicopathological and imaging features of these rare aneurysmal bone cyst variants, and discusses their diagnosis and treatment. The clinicians who treat patients with aneurysmal bone cysts should be familiar with these uncommon entities and their differential diagnosis.

Plexiform neurofibroma causing an ossifying subperiosteal haematoma: a rare case in the tibia of an 11-year-old girl

Ossifying subperiosteal haematoma is an exceedingly rare manifestation of Neurofibromatosis type 1 (NF-1). We report an interesting case of plexiform neurofibroma causing a rapidly growing tibial mass as a result of subperiosteal haemorrhage, in an 11-year-old girl with previously undiagnosed NF-1. This reflects a precursor of the more mature periosteal ossification seen in cases traditionally termed "subperiosteal cysts". A previously well young girl was referred by her general practitioner with an increasingly large, mildly tender, soft lump on the anterior aspect of her right tibia. Plain radiographs demonstrated soft tissue thickening overlying the anterior tibia, without appreciable periosteal ossification. Magnetic resonance imaging (MRI) illustrated a single central fluid-fluid level and periosteal elevation with saucerisation of the anterior tibial cortex and mild surrounding oedema. Histopathology revealed a large plexiform neurofibroma. Interestingly, this was associated with haemorrhagic change and a peripheral rim of florid reactive new bone formation. This unusual presentation was discussed at a multidisciplinary bone and soft tissue tumour meeting, where in combination with the clinical history of café au lait spots and positive family history, a consensus diagnosis of NF-1 was made. To date, there have only been limited case reports of this rare pathological process. In summary, this case report accounts an acute presentation of this rare osseous manifestation of NF-1, being the first to clearly demonstrate a timeline of subperiosteal haematoma with subsequent subperiosteal bone proliferation. The clinical reasoning and radiological features for such a presentation are also described.

Surface Aneurysmal Bone Cyst: Clinical and Imaging Features in 10 New Cases

Aneurysmal bone cyst originating from the surface of the bone, either within the cortex or subperiosteally, is an uncommon anatomic subtype. This article reports the clinical and radiologic evaluations and treatment outcomes of 10 patients with surface aneurysmal bone cysts that were surgically treated between 1982 and 2014. Mean age at the time of surgery was 22.4 years (range, 11-44 years). According to Capanna's radiographic evaluation criteria, 6 of the lesions were classified as type V and 4 were classified as type IV. Radiographically, periosteal shell formation was observed to be complete in 4 patients, partial in 3, and absent in 3, and 6 patients had Codman's angle or buttress formation. In 1 patient, computed tomography scan showed birdcage-like ossification attached to the surface of bone. Magnetic resonance imaging showed fluid-fluid levels in 5 patients. All of the patients had standard curettage and high-speed burr application as an adjuvant. No patient had local recurrence at the end of the follow-up period of 98.4 months (range, 13-288 months). These findings show the importance of careful radiologic evaluation and biopsy to better plan a treatment strategy when surface aneurysmal bone cyst is included in the differential diagnosis. The finding of fluid-fluid levels on magnetic resonance imaging or computed tomography is not pathognomonic for primary aneurysmal bone cyst; however, the absence of this finding does not rule out the diagnosis. The rate of local recurrence after curettage plus high-speed burr is reasonably low, and other adjuvant procedures should be used whenever needed. [Orthopedics. 2016; 39(5):e897-e903.].

Surface primary bone tumors: Systematic approach and differential diagnosis

Surface primary bone tumors may appear similar to their intramedullary counterpart, but because they are rare, they may pose diagnostic challenges when showing different characteristics compared to their intramedullary counterpart. It is important for radiologists to recognize the imaging findings for various uncommon surface primary bone tumors, which may help to reduce the differential diagnosis or to lead to a specific diagnosis. Radiography is typically used for first-line imaging. If necessary, it is followed by CT or MRI for evaluation and characterization of surface bone tumors. The aim of this article is to review the imaging findings and differential diagnosis for surface primary bone tumors.

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In contrast to the intramedullary (80%) and intracortical (14%) subtypes, the subperiostal subtype of aneurysmatic bone cysts (sABC) is relatively rare (6%). Females are affected more frequently than males, whereby the diaphysis is predominantly affected and less frequently the metaphysis of long bones as well as the vertebral column. Especially in conventional radiography sABCs can mimic aggressive lesions. Cross-sectional imaging can potentially reduce the wide range of differential diagnoses. Due to typical imaging features magnetic resonance imaging (MRI) is the most valuable modality to reduce the range of possible differential diagnoses. MRI usually presents a multicystic appearance with a hypointense rim of the lesion, contrast-enhancing cyst walls, fluid levels and edema-like changes in the adjacent tissue. In sABCs with solid components the diagnosis cannot be made with confidence and the suspicion must be confirmed by biopsy. The therapy of primary lesions consists of curettage or the complete excision of the sABC and the defects are subsequently filled with spongiosa or bone cement depending on the size of the lesion.

Fibrocystic Changes at Anterosuperior Femoral Neck: Prevalence in Hips with Femoroacetabular Impingement

PURPOSE

To retrospectively evaluate if there is an association between juxta-articular fibrocystic changes at the anterosuperior femoral neck and femoroacetabular impingement (FAI).

MATERIALS AND METHODS

The institutional review board approved this study and did not require informed patient consent. An orthopedic surgeon and a radiologist in consensus retrospectively reviewed the anteroposterior (AP) pelvic radiographs of 117 hips with FAI and compared these images with the AP radiographs of a control group of 132 hips with developmental dysplasia (DD) to determine the prevalence of juxta-articular fibrocystic changes at the anterosuperior femoral neck. Criteria for juxta-articular fibrocystic changes at the anterosuperior femoral neck were location close to the physis and a diameter (of the fibrocystic change) of greater than 3 mm. The sensitivity and specificity of AP pelvic radiography in the detection of these fibrocystic changes were calculated by using an additional 61 hips with FAI and on the basis of findings at magnetic resonance (MR) arthrography, which was routinely performed for assessment of FAI. In 24 patients who underwent joint-preserving surgery for FAI, the fibrocystic changes were localized intraoperatively and the spatial relation of the region of these changes to the area of FAI was identified. Joint-preserving surgery consisted of anterior surgical dislocation of the hip with osteochondroplasty of the proximal femur and/or the acetabular rim to improve the impingement-free range of hip motion. For statistical comparisons, nonparametric tests were performed.

RESULTS

Fibrocystic changes were identified on the AP radiographs of 39 (33%) of the 117 FAI-affected hips and on none of the radiographs of the 132 DD-affected hips. According to MR arthrogram findings, the sensitivity, specificity, and positive and negative predictive values of AP pelvic radiography were 64%, 93%, 91%, and 71%, respectively. The mean diameter of the juxta-articular fibrocystic changes was 5 mm (range, 3-15 mm); smaller lesions were more prevalent. Dynamic MR imaging with the hip flexed and intraoperative observations revealed a close spatial relationship between the region of the fibrocystic changes at the anterosuperior femoral neck and the acetabular rim.

CONCLUSION

The high prevalence of juxta-articular fibrocystic changes at the anterosuperior femoral neck and their spatial relation to the impingement site suggest an association and possible causal relationship between these alterations and FAI.