Aggressive embryonal rhabdomyosarcoma in a 3-month-old boy: A clinical and molecular analysis

Rhabdomyosarcoma (RMS) represents the most common soft tissue sarcoma in the pediatric age group. While RMS has been traditionally classified on the basis of its histological appearance (with embryonal and alveolar being most common), it is now clear that the PAX-FOXO1 fusion product drives prognosis. We report here a case of pelvic embryonal RMS in a 3-month-old male who was subsequently found to have developed brain metastases during the course of chemotherapy. Cytogenetic analysis of the brain metastases at the time of autopsy as well as next-generation sequencing analysis revealed a reciprocal translocation involving the SH3 domain containing ring finger 3 gene (SH3RF3, on chromosome 2q13) and the Lipase C gene (LIPC, on chromosome 15q21.3). Due to the poor quality of the pretreatment and postresection samples, cytogenetics and NGS analysis looking for the presence of this balanced translocation in these specimens could not be performed. To the authors' knowledge, this translocation has never been described in RMS. Further studies are needed to determine the biological and clinical implications of this novel translocation.

Mechanical stability of the cell nucleus - roles played by the cytoskeleton in nuclear deformation and strain recovery

Extracellular forces transmitted through the cytoskeleton can deform the cell nucleus. Large nuclear deformations increase the risk of disrupting the integrity of the nuclear envelope and causing DNA damage. The mechanical stability of the nucleus defines its capability to maintain nuclear shape by minimizing nuclear deformation and allowing strain to be minimized when deformed. Understanding the deformation and recovery behavior of the nucleus requires characterization of nuclear viscoelastic properties. Here, we quantified the decoupled viscoelastic parameters of the cell membrane, cytoskeleton, and the nucleus. The results indicate that the cytoskeleton enhances nuclear mechanical stability by lowering the effective deformability of the nucleus while maintaining nuclear sensitivity to mechanical stimuli. Additionally, the cytoskeleton decreases the strain energy release rate of the nucleus and might thus prevent shape change-induced structural damage to chromatin.

Cell ingression: Relevance to limb development and for adaptive evolution

Cell ingression is an out-of-plane type of cell intercalation that is essential for the formation of multiple embryonic structures including the limbs. In particular, cell ingression underlies epithelial-to-mesenchymal transition of lateral plate cells to initiate limb bud growth, delamination of neural crest cells to generate peripheral nerve sheaths, and emigration of myoblasts from somites to assemble muscles. Individual cells that ingress undergo apical constriction to generate bottle shaped cells, diminish adhesion to their epithelial cell neighbors, and generate protrusive blebs that likely facilitate their ingression into a subepithelial tissue layer. How signaling pathways regulate the progression of delamination is important for understanding numerous developmental events. In this review, we focus on cellular and molecular mechanisms that drive cell ingression and draw comparisons between different morphogenetic contexts in various model organisms. We speculate that cell behaviors that facilitated tissue invagination among diploblasts subsequently drove individual cell ingression and epithelial-to-mesenchymal transition. Future insights that link signalling pathways to biophysical mechanisms will likely advance our comprehension of this phenomenon.

Cell and Tissue Scale Forces Coregulate Fgfr2-Dependent Tetrads and Rosettes in the Mouse Embryo

What motivates animal cells to intercalate is a longstanding question that is fundamental to morphogenesis. A basic mode of cell rearrangement involves dynamic multicellular structures called tetrads and rosettes. The contribution of cell-intrinsic and tissue-scale forces to the formation and resolution of these structures remains unclear, especially in vertebrates. Here, we show that Fgfr2 regulates both the formation and resolution of tetrads and rosettes in the mouse embryo, possibly in part by spatially restricting atypical protein kinase C, a negative regulator of non-muscle myosin IIB. We employ micropipette aspiration to show that anisotropic tension is sufficient to rescue the resolution, but not the formation, of tetrads and rosettes in Fgfr2 mutant limb-bud ectoderm. The findings underscore the importance of cell contractility and tissue stress to multicellular vertex formation and resolution, respectively.

Structural components of nuclear integrity with gene regulatory potential

The nucleus is a mechanosensitive and load-bearing structure. Structural components of the nucleus interact to maintain nuclear integrity and have become subjects of exciting research that is relevant to cell and developmental biology. Here we outline the boundaries of what is known about key architectural elements within the nucleus and highlight their potential structural and transcriptional regulatory functions.

The two domain hypothesis of limb prepattern and its relevance to congenital limb anomalies

Functional annotation of mutations that cause human limb anomalies is enabled by basic developmental studies. In this study, we focus on the prepatterning stage of limb development and discuss a recent model that proposes anterior and posterior domains of the early limb bud generate two halves of the future skeleton. By comparing phenotypes in humans with those in model organisms, we evaluate whether this prepatterning concept helps to annotate human disease alleles. WIREs Dev Biol 2017, 6:e270. doi: 10.1002/wdev.270 For further resources related to this article, please visit the WIREs website.

Anisotropic stress orients remodelling of mammalian limb bud ectoderm

The physical forces that drive morphogenesis are not well characterized in vivo, especially among vertebrates. In the early limb bud, dorsal and ventral ectoderm converge to form the apical ectodermal ridge (AER), although the underlying mechanisms are unclear. By live imaging mouse embryos, we show that prospective AER progenitors intercalate at the dorsoventral boundary and that ectoderm remodels by concomitant cell division and neighbour exchange. Mesodermal expansion and ectodermal tension together generate a dorsoventrally biased stress pattern that orients ectodermal remodelling. Polarized distribution of cortical actin reflects this stress pattern in a β-catenin- and Fgfr2-dependent manner. Intercalation of AER progenitors generates a tensile gradient that reorients resolution of multicellular rosettes on adjacent surfaces, a process facilitated by β-catenin-dependent attachment of cortex to membrane. Therefore, feedback between tissue stress pattern and cell intercalations remodels mammalian ectoderm.

Congenital infantile fibrosarcoma: review of imaging features

BACKGROUND

Fibrosarcoma is a rare tumor in children with limited information on imaging features of these tumors in the literature.

OBJECTIVE

To retrospectively review the imaging features of histologically proven congenital infantile fibrosarcoma.

MATERIALS AND METHODS

The list of histologically confirmed congenital infantile fibrosarcomas between November 1999 and June 2013 was obtained from the oncology-pathology database. Imaging features and pathology reports of these tumors were reviewed. Patient charts were reviewed and clinical features, management and outcomes were recorded.

RESULTS

During the study period, 13 children (9 girls and 4 boys; age range: 0 day-16 months, median age: 2.5 months) with congenital infantile fibrosarcomas were available for complete radiological review. The translocation (t[12;15]) was present in 11/13 (84.6%) and absent in 2/13. Eight/thirteen (61.5%) tumors were located in extremities (5 in lower and 3 in upper), 3/13 in thoracolumbar paraspinal regions, and one each in abdomen and sternocleidomastoid muscle. Imaging features included iso- to hyperintensity on T1-W, hyperintensity on T2-W as compared to skeletal muscles and heterogeneous enhancement. Six (37.5%) tumors showed hemorrhagic components and 2 (15.4%) showed low intensity foci. None of the patients had evidence of regional or distant metastases at diagnosis. Management included surgical resection only (1/13) and combined surgery and chemotherapy (10/13). Overall survival was 100% with a median follow-up of 49.3 months.

CONCLUSION

Congenital infantile fibrosarcoma has nonspecific imaging characteristics but should be high on the differential diagnosis in a soft-tissue tumor presenting in infancy, located in an extremity and showing tumoral hemorrhage. Patients have a favorable outcome.

Can neonatal pelvic osteotomies permanently change pelvic shape in patients with exstrophy? Understanding late rediastasis

BACKGROUND

Pelvic osteotomies are frequently used as part of the surgical management of bladder exstrophy. The outcomes are often measured on the basis of the residual symphyseal diastasis. The aims of this study were to evaluate and validate a more reliable radiographic measure of ischiopubic rotation, to utilize this measure in analyzing pelves from patients with exstrophy and controls, and to propose a model for rediastasis in a pelvis with exstrophy.

METHODS

Pelvic radiographs of 164 normal children two months to eighteen years of age were used to determine the changes in interpubic and interischial distances and in the interischial/interpubic (IS/IP) ratio with age. Twenty-one pelvic CT (computed tomography) studies of normal children, two to sixteen years of age, were also used to study the change in the ischiopubic divergence angle. The same parameters were measured on radiographs or CT or magnetic resonance imaging studies of seventy-three patients with classic bladder exstrophy who were followed for two to nineteen years after exstrophy closure with or without pelvic osteotomies.

RESULTS

In normal children, the interpubic distance and the ischiopubic divergence angle had a narrow range and were constant with age, whereas the interischial distance and the IS/IP ratio increased progressively and were strongly correlated with age. In the patients with exstrophy, the interpubic distance was positively correlated with the interischial distance, whereas the IS/IP ratio was lower than that in normal controls and was not correlated with age.

CONCLUSIONS

The IS/IP ratio is a useful measure of ischiopubic rotation and can be used to characterize pelvic growth, including the phenomenon of rediastasis in patients with exstrophy. Pelvic rediastasis is a progressive increase in interpubic distance resulting from growth without loss of rotational correction, as shown by the constancy of the IS/IP ratio with age in these patients. A better rotational position at the time of osteotomy may lead to a better pelvic shape at maturity.

CLINICAL RELEVANCE

Symphyseal rediastasis following neonatal pelvic osteotomies in patients with exstrophy is not due to loss of correction and progressive derotation of the hemipelves but is a consequence of the normal three-dimensional growth of the pelvis. The best correction of the pelvic deformity should always be the aim even in neonatal pelvic osteotomies because this will permanently change the pelvic shape.

In situ mechanical characterization of the cell nucleus by atomic force microscopy

The study of nuclear mechanical properties can provide insights into nuclear dynamics and its role in cellular mechanotransduction. While several methods have been developed to characterize nuclear mechanical properties, direct intracellular probing of the nucleus in situ is challenging. Here, a modified AFM (atomic force microscopy) needle penetration technique is demonstrated to mechanically characterize cell nuclei in situ. Cytoplasmic and nuclear stiffness were determined based on two different segments on the AFM indentation curves and were correlated with simultaneous confocal Z-stack microscopy reconstructions. On the basis of direct intracellular measurement, we show that the isolated nuclei from fibroblast-like cells exhibited significantly lower Young's moduli than intact nuclei in situ. We also show that there is in situ nucleus softening in the highly metastatic bladder cancer cell line T24 when compared to its less metastatic counterpart RT4. This technique has potential to become a reliable quantitative measurement tool for intracellular mechanics studies.

Formation of proximal and anterior limb skeleton requires early function of Irx3 and Irx5 and is negatively regulated by Shh signaling

Limb skeletal pattern relies heavily on graded Sonic hedgehog (Shh) signaling. As a morphogen and growth cue, Shh regulates identities of posterior limb elements, including the ulna/fibula and digits 2 through 5. In contrast, proximal and anterior structures, including the humerus/femur, radius/tibia, and digit 1, are regarded as Shh independent, and mechanisms governing their specification are unclear. Here, we show that patterning of the proximal and anterior limb skeleton involves two phases. Irx3 and Irx5 (Irx3/5) are essential in the initiating limb bud to specify progenitors of the femur, tibia, and digit 1. However, these skeletal elements can be restored in Irx3/5 null mice when Shh signaling is diminished, indicating that Shh negatively regulates their formation after initiation. Our data provide genetic evidence supporting the concept of early specification and progressive determination of anterior limb pattern.

A switch from low to high Shh activity regulates establishment of limb progenitors and signaling centers

The patterning and growth of the embryonic vertebrate limb is dependent on Sonic hedgehog (Shh), a morphogen that regulates the activity of Gli transcription factors. However, Shh expression is not observed during the first 12 hr of limb development. During this phase, the limb bud is prepatterned into anterior and posterior regions through the antagonistic actions of transcription factors Gli3 and Hand2. We demonstrate that precocious activation of Shh signaling during this early phase interferes with the Gli3-dependent specification of anterior progenitors, disturbing establishment of signaling centers and normal outgrowth of the limb. Our findings illustrate that limb development requires a sweet spot in the level and timing of pathway activation that allows for the Shh-dependent expansion of posterior progenitors without interfering with early prepatterning functions of Gli3/Gli3R or specification of anterior progenitors.

Development and testing of a multidimensional iPhone pain assessment application for adolescents with cancer

Background

Pain is one of the most common and distressing symptoms reported by adolescents with cancer. Despite advancements in pain assessment and management research, pain due to cancer and/or its treatments continues to be poorly managed. Our research group has developed a native iPhone application (app) called Pain Squad to tackle the problem of poorly managed pain in the adolescent with cancer group. The app functions as an electronic pain diary and is unique in its ability to collect data on pain intensity, duration, location, and the impact pain has on an adolescent’s life (ie, relationships, school work, sleep, mood). It also evaluates medications and other physical and psychological pain management strategies used. Users are prompted twice daily at configurable times to complete 20 questions characterizing their pain and the app transmits results to a database for aggregate reporting through a Web interface. Each diary entry represents a pain case filed by an adolescent with cancer and a reward system (ie, moving up through law-enforcement team ranks, built-in videotaped acknowledgements from fictitious officers) encourages consistent use of the diary.

Objective

Our objective was to design, develop, and test the usability, feasibility, compliance, and satisfaction of a game-based smartphone pain assessment tool for adolescents with cancer.

Methods

We used both low- and high-fidelity qualitative usability testing with qualitative semi-structured, audio-taped interviews and iterative cycles to design and refine the iPhone based Pain Squad app. Qualitative thematic analysis of interviews using constant comparative methodology captured emergent themes related to app usability. Content validity was assessed using question importance-rating surveys completed by participants. Compliance and satisfaction data were collected following a 2-week feasibility trial where users were alarmed to record their pain twice daily on the app.

Results

Thematic analysis of usability interviews showed the app to be appealing overall to adolescents. Analyses of both low- and high-fidelity testing resulted in minor revisions to the app to refine the theme and improve its usability. Adolescents resoundingly endorsed the game-based nature of the app and its virtual reward system. The importance of app pain diary questions was established by content validity analysis. Compliance with the app, assessed during feasibility testing, was high (mean 81%, SD 22%) and adolescents from this phase of the study found the app likeable, easy to use, and not bothersome to complete.

Conclusions

A multifaceted usability approach demonstrated how the Pain Squad app could be made more appealing to children and adolescents with cancer. The game-based nature and built-in reward system of the app was appealing to adolescents and may have resulted in the high compliance rates and satisfaction ratings observed during clinical feasibility testing.

Combined glenoid anteversion osteotomy and tendon transfers for brachial plexus birth palsy: early outcomes

BACKGROUND

In the setting of severe glenohumeral dysplasia secondary to brachial plexus birth palsy, external rotation osteotomy of the humerus has traditionally been used to transpose the existing arc of shoulder motion to a more functional position. Here we introduce a surgical alternative, the aim of which is to gain stable reduction of the shoulder and restore active external rotation.

METHODS

All patients with brachial plexus birth palsy and Waters type-III, IV, or V glenohumeral dysplasia who underwent glenoid anteversion osteotomy combined with tendon transfers between 2006 and 2009 were identified. The Mallet score, Active Movement Scale, and active and passive ranges of motion were used to assess functional outcomes. Axial imaging was used to measure glenoid version, the degree of subluxation, and the Waters type.

RESULTS

Thirty-two patients with a median age of 6.8 years (range, 2.1 to 16.2 years) were followed for a mean of twenty months (range, twelve to twenty-nine months). On average, passive external rotation with the shoulder in neutral increased by 43° (95% confidence interval [CI], 26° to 60°), passive internal rotation decreased by 22° (95% CI, 12° to 31°), active external rotation with the shoulder in neutral increased by 82° (95% CI, 66° to 98°), and active internal rotation decreased by 26° (95% CI, 14° to 38°). The aggregate Mallet score improved by a mean of 4.0 points (95% CI, 3.0 to 4.9). Glenoid retroversion improved by a mean of 26° (95% CI, 20° to 32°). The percentage of the humeral head anterior to the midscapular line improved by a mean of 35% (95% CI, 30% to 40%).

CONCLUSIONS

In patients with severe glenohumeral dysplasia, glenoid realignment osteotomy in conjunction with soft-tissue rebalancing permits maintenance of joint reduction and functional improvement in the short term. In our view, external rotation osteotomy of the humerus is no longer the only surgical option for these cases.

Combined Glenoid Anteversion Osteotomy and Tendon Transfers for Brachial Plexus Birth Palsy

Introduction

Combined glenoid osteotomy with tendon transfers is a new alternative procedure for patients with severe glenohumeral dysplasia secondary to brachial plexus birth palsy.

Step 1 MRI or CT for Preoperative Planning

Use axial plane MRI or CT for preoperative planning.

Step 2 Surgical Approach with Deltoid Elevation

Position the patient laterally, and undertake a posterior approach, including lateral elevation of the deltoid origin.

Step 3 Subscapularis Slide

Elevate the subscapularis from the scapula, provisionally reduce the humeral head, and apply gentle external rotation.

Step 4 Harvest of the Teres Major and Latissimus Dorsi Tendons

Incise the insertions of the teres major and latissimus dorsi from the proximal part of the humerus and perform a tenolysis.

Step 5 Posterior Approach to the Glenohumeral Joint

Open the posterior glenohumeral joint and assess overhead elevation.

Step 6 Assessment and Improvement of Abduction Contracture

Improve abduction contracture if it is marked.

Step 7 Harvest of Bone Graft

Harvest tricortical graft from the scapular spine or posterior aspect of the acromion.

Step 8 Scapular Neck Osteotomy

Undertake a posterior opening wedge osteotomy of the scapular neck.

Step 9 Posterior Opening Wedge at the Osteotomy Site

Insert the bone graft into the osteotomy site.

Step 10 Joint Closure and Infraspinatus Repair

Close the posterior aspect of the capsule and the infraspinatus.

Step 11 Transfer of the Teres Major and Latissimus Dorsi

Transfer the teres major and latissimus dorsi tendons into an osseous trough at the greater tuberosity.

Step 12 Closure and Immobilization

Repair the deltoid, close the wound in layers, and apply a shoulder spica cast.

Step 13 Postoperative Plan

Maintain the spica cast for five to six weeks; then initiate physiotherapy.

Results

In our series of thirty-two patients with severe glenohumeral dysplasia who underwent combined glenoid osteotomy and tendon transfers, early results suggest that the outcomes of this procedure are similar to those of proximal humeral external rotation osteotomy¹.

What to Watch For

IndicationsContraindicationsPitfalls & Challenges.

Effects of neoadjuvant chemotherapy on image-directed planning of surgical resection for distal femoral osteosarcoma

BACKGROUND

Standard therapy for localized osteosarcoma includes neoadjuvant chemotherapy preceding local control surgery, followed by adjuvant chemotherapy. When limb-salvage procedures were being developed, preoperative chemotherapy allowed a delay in definitive surgery to permit fabrication of custom endoprosthetic reconstruction implants. One rationale for its continuation as the care standard has been the perception that it renders surgery easier and safer. Our objective was to compare surgical procedures planned on the basis of magnetic resonance images (MRIs) of distal femoral osteosarcomas acquired before neoadjuvant chemotherapy with surgical procedures planned on the basis of MRIs acquired after neoadjuvant chemotherapy as a measure of the surgically critical anatomic effects of the chemotherapy.

METHODS

Twenty-four consecutive patients with distal femoral osteosarcoma had available digital MRIs preceding and following neoadjuvant chemotherapy. Thorough questionnaires were used to catalogue surgically critical anatomic details of MRI-directed surgical planning. Four faculty musculoskeletal oncologic surgeons and two musculoskeletal radiologists evaluated the blinded and randomly ordered MRIs. Interrater and intrarater reliabilities were calculated with intraclass correlation coefficients. The Student t test and chi-square test were used to compare pre-chemotherapy and post-chemotherapy continuous and categorical variables on the questionnaire. Mixed-effect regression models were employed to compare surgical procedures planned on the basis of pre-chemotherapy MRIs and with those planned on the basis of post-chemotherapy MRIs.

RESULTS

The blinded reviews generated strong intraclass correlation coefficients for both interrater (0.772) and mean intrarater (0.778) reliability. The MRI-planned resections for the majority of tumors changed meaningfully after chemotherapy, but in inconsistent directions. On the basis of mixed-effect regression modeling, it appeared that more amputations were planned on the basis of post-chemotherapy MRIs. No other parameters differed in a significant and clinically meaningful fashion. Surgeons demonstrated their expectation that neoadjuvant chemotherapy would improve resectability by planning more radical surgical procedures on the basis of scans that they predicted had been obtained pre-chemotherapy.

CONCLUSIONS

Surgeons can reliably record the anatomic details of a planned resection of an osteosarcoma. Such methods may be useful in future multi-institutional clinical trials or registries. The common belief that neoadjuvant chemotherapy increases the resectability of extremity osteosarcomas remains anecdotally based. Rigorous assessment of this phenomenon in larger cohorts and at other anatomic sites as well as re-evaluation of other arguments for neoadjuvant chemotherapy should be considered.

Ezh2 regulates anteroposterior axis specification and proximodistal axis elongation in the developing limb

Specification and determination (commitment) of positional identities precedes overt pattern formation during development. In the limb bud, it is clear that the anteroposterior axis is specified at a very early stage and is prepatterned by the mutually antagonistic interaction between Gli3 and Hand2. There is also evidence that the proximodistal axis is specified early and determined progressively. Little is known about upstream regulators of these processes or how epigenetic modifiers influence axis formation. Using conditional mutagenesis at different time points, we show that the histone methyltransferase Ezh2 is an upstream regulator of anteroposterior prepattern at an early stage. Mutants exhibit posteriorised limb bud identity. During later limb bud stages, Ezh2 is essential for cell survival and proximodistal segment elongation. Ezh2 maintains the late phase of Hox gene expression and cell transposition experiments suggest that it regulates the plasticity with which cells respond to instructive positional cues.

Budding behaviors: Growth of the limb as a model of morphogenesis

Questions regarding morphogenesis have played second fiddle to those pertaining to pattern formation among the limb development set for some time. A recent series of publications has reinvigorated the search for mechanisms by which the limb bud arises, elongates and acquires its peculiar shape. While there are stage-specific variations, the theme that resonates across these studies is that mesoderm and cartilage cells in the limb bud exhibit polarity that drives directional movement and oriented division. Noncanonical Wnt signalling is important for these cell behaviors at all stages of limb development. While the emerging morphogenetic mechanisms underlying limb bud outgrowth are partly analogous to those of other developing structures, insights from the limb have the potential to reveal intriguing new mechanisms by which three dimensional mesoderm changes shape.