Interobserver reliability in the histopathological diagnosis of cartilaginous tumors in patients with multiple osteochondromas

Cartilage Forming Tumors of the Skeleton

Cartilage-forming tumors are a broad and diverse group of neoplasms frequently affecting the skeleton. Distinguishing between the members of this group is important because of significant differences in treatment and prognosis. Accurate diagnosis can be challenging because of similarities in their clinical, radiographic, and pathologic features. Immunohistochemistry and molecular tools are helpful in select instances. Therefore, careful evaluation and correlation of these features are essential in arriving at the correct diagnosis and appropriate patient management. This review provides an overview of the current literature, emphasizing helpful features in diagnosis.

Malignant transformation of osteochondroma to chondrosarcoma: a challenging case

A 50-year-old female presented with a large palpable mass in the right buttock and proximal thigh, accompanied by sciatic paresthesia. She reported intermittent thigh and knee pain for 5 years, worsening over the previous 6 months. Plain radiography images revealed a pedunculated osteochondroma on the posterolateral aspect of the femur with extensive soft tissue involvement and soft tissue calcifications. A computed tomography (CT) scan showed an osteochondroma with a large adjacent bursa containing multiple foci of calcifications with a "snowstorm" appearance. A diagnostic dilemma arose regarding whether the condition represented reactive bursitis secondary to osteochondroma or a malignant transformation to chondrosarcoma with intra-bursal invasion. Magnetic resonance imaging (MRI) indicated a thick cartilage cap of osteochondroma measuring 53 mm and multiple cartilage nodules in the bursa along with heterogeneous enhancement in cartilage islands. Moreover, evidence of adjacent muscle invasion and sciatic nerve encasement was noted. These findings suggested an unusual diagnosis of malignant transformation of the osteochondroma to chondrosarcoma with intra-bursal invasion. The patient underwent wide-margin resection of the proximal femur and tumoral soft tissue, reconstructed with a proximal femoral mega prosthesis. Histologic evaluation confirmed a well-differentiated chondrosarcoma with intra-bursal invasion. This case highlights the critical role of diagnostic imaging in differentiating between benign and malignant complications associated with osteochondroma.

The Role of Routine Pathologic Assessment After Pediatric Osteochondroma Excision

BACKGROUND

Osteochondromas are benign osseous lesions often excised for pain, growth abnormalities, and aesthetic concerns. While characteristic clinical and radiographic features leave little diagnostic ambiguity in most cases of osteochondroma, pathologic analysis to confirm the diagnosis and screen for malignancy is routinely performed following surgical excision. The purpose of this study was to determine the clinical and economic value of routine pathologic analysis after osteochondroma excision in a pediatric population.

METHODS

A retrospective review of clinical records from 2 pediatric orthopaedic hospitals (St. Louis Children's Hospital and Shriner's Hospital for Children, St. Louis) identified 426 osteochondroma lesions surgically resected from 201 patients. Patients with solitary and multiple lesions were included. Clinical, radiographic, and surgical data were recorded for each resection surgery. Pathologic reports were evaluated. Costs incurred for routine pathologic assessment was also noted.

RESULTS

Totally, 132 patients were treated with surgical resection of a solitary osteochondroma lesion, while an additional 291 lesions were resected from 69 patients with multiple lesions. Average age at the time of surgical resection was 13.0 years (2.1 to 17.9). The most common anatomic locations of excised lesions included the distal femur (110, 25.8%), proximal tibia/fibula (95, 22.3%), and distal radius/ulna (58, 13.6%). All resected specimens were sent for pathologic analysis. The average size of the resected lesions was 19.9 mm 3 (0.02 to 385.0 mm 3 ). In all cases, the histologic diagnosis confirmed benign osteochondroma. The total charges of pathologic analysis including processing and interpretation fees was ∼$755.00 for each lesion assessed, for a total cohort charge of $321,630.

CONCLUSION

We propose that in most cases of pediatric osteochondroma excision procedures, postoperative histologic analysis is not strictly indicated as it rarely, if ever, alters diagnosis or management. We suggest using a "gross only" analysis in these cases. However, we do believe that with preoperative diagnostic ambiguity, or if patients present with concerning features such as rapidly expansile lesions or cortical destruction, have axial skeleton or pelvic involvement, or enlarged cartilaginous caps, full histologic evaluation of the excised lesions will continue to be prudent.

LEVEL OF EVIDENCE

Level IV-case series.

Dedifferentiation in bone and soft tissue sarcomas: How do we define it? What is prognostically relevant?

Dedifferentiation traditionally is defined by descriptive criteria as a tumor showing an abrupt change in histology from a conventional, classic, low-grade appearing neoplasm to a tumor that is more cellular, pleomorphic and "high grade", with grading typically being performed by subjective criteria. The dedifferentiated areas range from areas with recognizable histologic differentiation which differs from the primary tumor (such as an osteosarcoma arising from a low-grade chondrosarcoma) to areas containing sarcomas without specific histologic differentiation (such as pleomorphic or spindle cell sarcoma). Many, but not all, dedifferentiated tumors are aggressive and associated with significantly shorter survival than their conventional counterparts, even grade 3 conventional tumors. As a result, dedifferentiated tumors are generally considered to be clinically aggressive and as a result, more aggressive surgery or the addition of (neo)adjuvant chemotherapy is often considered. However, long-term (greater than 20 year) survivors are reported in the most common dedifferentiated bone and soft tissue sarcomas. Moreover, use of mitotic criterion for defining dedifferentiation in dedifferentiated liposarcoma as well as grading (by the French system) have been found to be associated with survival. This paper reviews the literature on dedifferentiated chondrosarcoma, dedifferentiated liposarcoma, dedifferentiated chordoma and dedifferentiated parosteal osteosarcoma. As a result of that review, recommendations are advocated to identify evidence-based, objective diagnostic and grading criteria for dedifferentiation that are appropriate for each tumor type. Adding such criteria will improve consistency in diagnosis worldwide, allow easier comparison of clinical research performed on dedifferentiated tumors and help communicate (to patients and clinicians) the tumors with highest risk of clinically aggressive behavior, to allow appropriate and personalized treatment planning.

Secondary peripheral chondrosarcoma in multiple osteochondromas: a retrospective single-institution case series

BACKGROUND

Multiple osteochondromas is genetic disorder characterized by the formation of multiple benign cartilage-capped bone tumors, named osteochondromas, during skeletal development. The most feared complication is the secondary peripheral chondrosarcoma, a malignant cartilaginous neoplasm that arises from the chondroid cap of pre-existent osteochondromas. We conducted a retrospective cohort study on patients diagnosed and followed up from 1960 to 2019 to describe the clinical and pathological features of individuals affected by peripheral chondrosarcoma in multiple osteochondromas, to evaluate follow up information and individual outcome and to compare the results with literature. Data, including age, gender, site, histological grade, cartilage cap thickness, surgical treatments, surgical margins, genotype mutational status as well as treatment details were captured from the hospital electronic health records and from Registry of Multiple Osteochondromas. In addition, a complete histological review of all hematoxylin and eosin (H&E)-stained sections has been performed by expert pathologists.

RESULTS

One hundred five of the screened cases were included in the present study. The age at diagnosis of SPC ranges from 13 to 63, with median age at diagnosis of 34 years. The site most frequently affected by malignant degeneration was the pelvis (46 patients, 44%) with higher incidence in male patients (32 males vs.14 females). The second one was lower limbs (including femur, fibula, or tibia), identified in 35 patients. Histological information - available for 103 patients - showed: 59 patients with grade 1; 40 patients had a grade 2 and 4 patients had a grade 3. The most common surgical treatment was the complete resection, followed by debulking, amputation and partial resection. Most of cases did not have recurrence of the disease. Outcome in disease-free survival highlights that a worse course of the disease was associated with histological grade 2 or 3, and partial resection surgery. In most of analyzed cases (94%) a pathogenic variant was identified.

CONCLUSIONS

In conclusion, the present study gives an overview of the secondary peripheral chondrosarcomas, confirming that this disease represents an impacting complication for multiple osteochondromas patients and suggests that malignant transformation can occur also in younger patient, in a not irrelevant number of cases.

Tumor necrosis is an underappreciated histopathologic factor in the grading of chondrosarcoma

BACKGROUND

Cartilaginous neoplasms can be challenging to grade; there is a need to create an evidence-based rubric for grading. The goal of this study was to identify histopathologic features of chondrosarcoma that were associated with 5-year survival and to compare these to traditional patient, tumor and treatment variables.

METHODS

This was a retrospective review of all patients undergoing surgical resection of a primary chondrosarcoma with at least 2 years of follow up. All specimens were independently reviewed by two pathologists and histopathologic features scored. Univariate and multivariate analyses were performed utilizing Kaplan Meier and proportional hazards methods to identify variables associated with 5-year disease specific survival (DSS) and disease free survival (DFS).

RESULTS

We identified 51 patients with an average follow up of 49 months eligible for inclusion. 30% of tumors were low grade, 45% were intermediate grade, and 25% were high grade. In a univariate analysis considering histopathologic factors, higher tumor mitotic rate (HR 8.9, p < 0.001), tumor dedifferentiation (HR 7.3, p < 0.001), increased tumor cellularity (HR 5.8, p = 0.001), increased tumor atypia (HR 5.8, p = 0.001), LVI (HR 4.7, p = 0.04) and higher tumor necrosis (HR 3.7, p = 0.02) were all associated with worse 5-year DSS. In a multivariate analysis controlling for potentially confounding variables, higher tumor necrosis was significantly associated with disease specific survival survival (HR 3.58, p = 0.035); none of the factors were associated with DFS.

CONCLUSIONS

This study provides an evidence-based means for considering histopathologic markers and their association with prognosis in chondrosarcoma. Our findings suggest that necrosis and LVI warrant further study.

[Uncommon tumor-associated deep vein thrombosis]

Es wird über den Fall einer tiefen Beinvenenthrombose berichtet, bei dem im Rahmen der Diagnostik ein zuvor nicht bekanntes Chondrosarkom entdeckt wurde. In der körperlichen Untersuchung zeigte sich am rechten Knie dorsal eine feste, nicht verschiebliche Raumforderung, die in der Sonographie als zystische Formation imponierte. Röntgen, Computertomographie und Kernspintomographie zeigten typische Befunde einer sekundär entarteten kartilaginären Exostose, die sehr wahrscheinlich über lokale Kompression und ggf. über paraneoplastische Mechanismen die Entstehung der Thrombose begünstigt hatte. Nach Resektion des Tumors wurde die präoperativ begonnene Antikoagulation fortgeführt. In Zusammenschau aller Befunde wurde die endgültige Diagnose eines hochdifferenzierten sekundären Chondrosarkoms mit Thrombose der Poplitealvene gestellt.

Benign Cartilage-forming Tumors

Although uncommon in many pathology practices, cartilage-forming tumors represent some of the most frequent primary bone tumors. Diagnosis can be challenging given their variable histologic spectrum and the presence of overlapping morphologic, immunohistochemical, and genetic features between benign and malignant entities, particularly low-grade malignancies. Correlation with clinical findings and radiographic features is crucial for achieving an accurate diagnosis and appropriate clinical management, ranging from observation to excision. Tumors can be characterized broadly by their location in relation to the bone (surface or intramedullary). In specific instances, ancillary testing may help.

The 2020 WHO Classification of Tumors of Bone: An Updated Review

Bone tumors are a rare and heterogeneous group of neoplasms that occur in the bone. The diversity and considerable morphologic overlap of bone tumors with other mesenchymal and nonmesenchymal bone lesions can complicate diagnosis. Accurate histologic diagnosis is crucial for appropriate management and prognostication. Since the publication of the fourth edition of the World Health Organization (WHO) classification of tumors of soft tissue and bone in 2013, significant advances have been made in our understanding of bone tumor molecular biology, classification, prognostication, and treatment. Detection of tumor-specific molecular alterations can facilitate the accurate diagnosis of histologically challenging cases. The fifth edition of the 2020 WHO classification of tumors of soft tissue and bone tumors provides an updated classification scheme and essential diagnostic criteria for bone tumors. Herein, we summarize these updates, focusing on major changes in each category of bone tumor, the newly described tumor entities and subtypes of existing tumor types, and newly described molecular and genetic data.

Periosteal chondroma of pelvis - an unusual location

Periosteal chondroma is a slow growing benign tumor with prevalence rate of less than 2% of all chondromas. This tumor is mostly observed in clavicle, ribs and humerus and only one previous case has been reported in pelvis. Here we present an unusual case of periosteal chondroma due to uncommon presentation, location and age range. Our case is a 39 year-old male diagnosed with periosteal chondroma in pelvis. He had unspecific signs and symptoms overlapping with low back pain and disk herniation. By the time of admission he had gluteal muscle atrophy and also claudication. Differentiation of periosteal chondroma from other malignant tumors are pivotal in order to prevent aggressive and inappropriate therapies. He underwent surgical procedures and periosteal chondroma was ascertained by both radiological and Histopathological evidence. 6 months after surgery, he declared no pain, he was able to walk freely. He claimed partial paresthesia but he also declared that his paresthesia has ameliorated.

Differential Diagnosis of Cartilaginous Lesions of Bone

CONTEXT.—

Cartilaginous tumors represent one of the most common tumors of bone. Management of these tumors includes observation, curettage, and surgical excision or resection, depending on their locations and whether they are benign or malignant. They can be diagnostically challenging, particularly in small biopsies. In rare cases, benign tumors may undergo malignant transformation.

OBJECTIVE.—

To review common cartilaginous tumors, including in patients with multiple hereditary exostosis, Ollier disease, and Maffucci syndrome, and to discuss problems in the interpretation of well-differentiated cartilaginous neoplasms of bone. Additionally, the concept of atypical cartilaginous tumor/chondrosarcoma grade 1 will be discussed and its use clarified.

DATA SOURCES.—

PubMed (US National Library of Medicine, Bethesda, Maryland) literature review, case review of archival cases at the Massachusetts General Hospital, and personal experience of the authors.

CONCLUSIONS.—

This review has examined primary well-differentiated cartilaginous lesions of bone, including their differential diagnosis and approach to management. Because of the frequent overlap in histologic features, particularly between low-grade chondrosarcoma and enchondroma, evaluation of well-differentiated cartilaginous lesions should be undertaken in conjunction with thorough review of the imaging studies.

Risk stratification for central conventional chondrosarcoma of bone: A novel system predicting risk of metastasis and death in the Cancer Registry of Norway cohort

BACKGROUND AND OBJECTIVES

Interobserver variability in histological grading of central conventional chondrosarcoma (CCCS) limits the quality of patient information and research progression. We aim to quantify known and new prognostic variables and propose a risk stratification model.

METHOD

We selected 149 cases from the Cancer Registry of Norway. Cox proportional hazard models were estimated. Based on these results a dichotomous risk classification was proposed and presented by Kaplan-Meier estimates for rates of local recurrence, metastasis, and disease-specific survival.

RESULTS

The influence of axial skeletal location (Hazard ratio [HR] = 19.06), a soft tissue component ≥1 cm (HR = 13.45), and histological grade 3 (HR = 16.46) are all significant in predicting the rate of metastasis. The creation of a variable combining axial skeletal location and a soft tissue component ≥1 cm strongly predicts the risk of metastasis (HR = 14.02; P < .001) and death (HR = 2.74; P = .030) at multivariate analysis, making the histological grade insignificant. Together with metastasis at diagnosis (HR = 285.65; P < .001), this forms the basis of our proposed risk stratification, producing a small high-risk group (39 cases with 33% risk of metastasis) and a large low-risk group (103 cases with 2% risk of metastasis) without a histological grade.

CONCLUSION

Axial skeletal location and a soft tissue component ≥1 cm combined divides a CCCS cohort into low- and high-risk groups without a histological grade.

Uncommon tumors of temporomandibular joint: An institutional experience and review

BACKGROUND

The temporomandibular joint (TMJ) harbors a myriad of pathologic alterations including arthritides and benign and malignant neoplasms.

METHODS

Herein, we describe our institutional experience of some uncommon and unusual synovial pathologies of the TMJ along with a review of literature. We searched through the archives of department of pathology and institutional electronic medical record for specimens of TMJ between 1999 and 2019. Hematoxylin and eosin slides were reviewed and data (final diagnosis, age, gender, clinical presentation, tumor size, treatment modality, recurrence, and vital status) were collected.

RESULTS

A total of seven cases were identified including four cases of synovial chrondromatosis; and one case each of tenosynovial giant cell tumor, localized type, tenosynovial giant cell tumor, diffuse type, and synovial sarcoma.

CONCLUSIONS

The article emphasizes on the clinical, radiologic, pathologic, and molecular features of these uncommon entities. The differential diagnosis of each entity is also discussed. Current updates in the management are also reviewed.

Clinicopathological value of ErbB2 gene and protein expression in osteochondroma

OBJECTIVE

The aim of this study was to investigate ErbB2 expression in osteochondroma and its relationship with clinicopathologic features of osteochondroma, so as to identify a new biomarker for the malignant transformation potential of osteochondroma.

METHODS

Immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH) were used to investigate the expression status of ErbB2 protein and gene in 30 osteochondroma tissues and 20 non-neoplastic bone tissues. The association of ErbB2 gene and protein expression with clinicopathological parameters of osteochondroma was analyzed by using the χ2 test and Fishers exact test.

RESULTS

ErbB2 protein was found to be over-expressed in 4 of 30 (13.3%) osteochondromas and 1 of 20 (5%) non-neoplastic bone samples, which were not statistically significant (p=0.336). However, 13 of the 30 (43.3%) osteochondromas showed ErbB2 gene amplification, which was failed to be observed in any of the non-neoplastic bone tissue. ErbB2 gene amplification in osteochondroma was significantly higher compared with that in non-neoplastic bone tissue (p=0.001). In addition, the ErbB2 gene amplification was closely associated with clinical pathological parameters of osteochondroma, including high expression of cellularity (p=0.001), presence of binucleated cells (p=0.001), nuclear pleomorphism (p=0.003), calcification (p=0.002), nodularity (p=0.002), necrosis (p=0.009) and cartilage thickness (p=0.026). The association of the gene amplification with other clinicopathological parameters of osteochondroma, including permeation of trabecular bone, cystic/mucoid changes, mitosis, radiographic appearance, cap volume and subtype of osteochondroma was not observed. The over-expression of ErbB2 protein was not found to be associated with the above stated clinical pathological parameters of osteochondroma.

CONCLUSION

ErbB2 gene amplification was associated with adverse clinicopathological status of osteochondroma and could serve as an index for malignant conversion of osteochondroma. Further research is required to verify the predictive values of ErbB2 for osteochondroma.

LEVEL OF EVIDENCE

Level IV, Diagnostic Study.

[Challenges in the diagnosis of cartilage tumors : Morphological spectrum and molecular markers]

The morphological and clinico-biological spectrum of chondrogenic tumours is wide. Given the diversity of therapeutic approaches, the correctness of the histological diagnosis is of major importance. The aim of this review is to provide insights into the challenges and limitations of diagnostic approaches restricted to morphology and to underscore the importance of an interdisciplinary dialogue between surgeons, radiologists and pathologists. Beyond this, the value of molecular analyses introduced in bone tumor diagnostics in recent years is discussed.

Chondrosarcoma in Norway 1990-2013; an epidemiological and prognostic observational study of a complete national cohort

BACKGROUND

Knowledge of chondrosarcoma (CS) of bone to date is based on institutional reports and registry publications with limits in reporting, detail and quality of data.

METHOD

We have performed a retrospective search of CS of bone in the National Cancer Registry in Norway from 1990-2013, cross checked against local tumor databases with further quality control and supplementation of all data from clinical files. The time period is defined by the routine use of axial imaging in clinical practice. A total of 311 cases are included. We performed 108 pathological reviews and 223 radiological reviews. The manuscript was prepared according to the STROBE checklist for strengthening of observational studies. We performed uni-/multivariate cox analyses to define independent prognostic variables from the main cohort of central CS of bone.

RESULTS

The incidence of CS of bone in Norway is 2.85/million/yr. for both sexes overall, rising to 3.45/million/yr. in the last 5-year period. There is an increase in the most common central CS subtype, stronger for women than for men. Central CS had, in general 10-15% local recurrence rates, all evident by 5 years while metastasis rate increases with location and grade. Exceptions are extremity grade 1 CS which displayed no metastatic events and axial grade-3 disease with high rates (50%) of both local and metastatic relapse. Peripheral CS had limited metastatic potential (2%), but rates of local relapse (13%) continue to appear towards 10 years of follow up. Malignancy grade 3 independently predicts rate of metastasis and presence of soft tissue component predicts local recurrence, metastasis and survival.

CONCLUSION

Rates of local recurrence, metastasis and disease specific survival follow clear patterns depending on subtype, location and grade allowing better tailoring of follow-up regimes. Malignancy grade 3 and the presence of a soft tissue component independently predict behavior for central CS of bone.

One-stage surgical excision of a huge bilateral multiple osteochondroma of the hip: a case report

Osteochondroma or hereditary multiple exostoses is the most common benign bone tumor and is usually found in young patients. Osteochondromata of the proximal femur or hip have been reported in 30% to 90% of patients with hereditary multiple exostoses. This article presents a 25-year-old-male referred to our orthopedic clinic with a complaint of pain in both groins for the last four years which has deteriorated in the past 6 months by limitation of range of motion. Radiographic findings were consistent with huge hip osteochondroma and a histopathological report confirmed the diagnosis. This was a case of a huge bilateral osteochondroma of the hip originating from the posterior of the hips to the neck of the femur and hip joints and part of proximal of femur, that underwent one-stage surgical excision of the tumor with posterior approach and tumor resection. As we know, this case of bilateral huge hip osteochondromas has rarely been presented previously by someone who has undergone one-stage surgery treatment of a tumor this size. Bilateral hip osteochondroma is a rare condition and we showed that one-stage excision can be performed successfully.

Tumor Syndromes That Include Bone Tumors: An Update

Tumor syndromes, including bone neoplasias, are genetic predisposing conditions characterized by the development of a pattern of malignancies within a family at an early age of onset. Occurrence of bilateral, multifocal, or metachronous neoplasias and specific histopathologic findings suggest a genetic predisposition syndrome. Additional clinical features not related to the neoplasia can be a hallmark of specific genetic syndromes. Mostly, those diseases have an autosomal dominant pattern of inheritance with variable percentage of penetrance. Some syndromic disorders with an increased tumor risk may show an autosomal recessive transmission or are related to somatic mosaicism. Many genetic tumor syndromes are known. This update is specifically focused on syndromes predisposing to osteosarcoma and chondrosarcoma.

Integrating Morphology and Genetics in the Diagnosis of Cartilage Tumors

Cartilage-forming tumors of bone are a heterogeneous group of tumors with different molecular mechanisms involved. Enchondromas are benign hyaline cartilage-forming tumors of medullary bone caused by mutations in IDH1 or IDH2. Osteochondromas are benign cartilage-capped bony projections at the surface of bone. IDH mutations are also found in dedifferentiated and periosteal chondrosarcoma. A recurrent HEY1-NCOA2 fusion characterizes mesenchymal chondrosarcoma. Molecular changes are increasingly used to improve diagnostic accuracy in chondrosarcomas. Detection of IDH mutations or HEY1-NCOA2 fusions has already proved their immense value, especially on small biopsy specimens or in case of unusual presentation.

A diagnostic approach to popliteal fossa masses

There is a myriad of potential mass lesions that occur in the popliteal fossa, which present as palpable masses or are found incidentally on imaging. With a thorough knowledge and understanding of the appearances and locations of these different entities, one can narrow the differential diagnoses in the majority of cases. This will eliminate unnecessary additional investigations and enable a more rapid management. We present a review of frequently encountered and less common entities using an anatomical sieve, with the aim of providing a diagnostic approach to popliteal fossa masses.

Intralesional Versus Wide Resection of Low-Grade Chondrosarcomas of the Hand

PURPOSE

To report our experience with intralesional curettage (resection with positive margins) and amputation (resection with negative margins) of low-grade chondrosarcomas (LCS) of the hand.

MATERIALS AND METHODS

Skeletally mature patients treated surgically for LCS of the hand at our institutions were reviewed. Demographics and oncological history were collected. Results of the entire cohort and by treatment modality were analyzed radiographically, functionally (strength, Disabilities of the Arm, Shoulder, and Hand measure), cosmetically, and oncologically (recurrence, Musculoskeletal Tumor Society score, metastasis, and mortality rates).

RESULTS

Seventeen cases in 16 patients were identified. Nine patients were women. Average age at surgery was 43 years (range, 20-80 years). Mean follow-up was 18 years (range, 9-23 years). Six of the 17 lesions treated at different institutions with intralesional procedures presented as recurrent disease. We treated 3 with a repeat intralesional procedure and the remaining with wide resection. Recurrence incidence was the same in both groups. The remaining 11 new-onset cases were treated with intralesional procedures (6) or wide resections (5). One of the 6 tumors treated with an intralesional procedure recurred. None treated with wide resection recurred. Recurrence incidence combining new- onset and recurrent disease after intralesional procedures was 22% versus 13% for wide resections. Average grip strength was 37 kg (range, 21-55 kg), and pinch strength was 7.6 kg (range, 4.5-12.5 kg). Mean Disabilities of the Arm, Shoulder, and Hand score was 2 (range, 0-10). There were no wound complications, and appearance was satisfactory in most cases (visual analog scale score, > 8). Average Musculoskeletal Tumor Society score was 29 points (range, 21-30 points). No patients presented with metastatic disease or died because of LCS.

CONCLUSIONS

Intralesional resections aiming to preserve function are safe, recognizing that more than 1 procedure may be required. Amputation also plays a role with excellent functional outcome in cases in which severe joint deformity or involvement of soft tissues and neurovascular structures interferes with function.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Solitary synovial chondromatosis arising in the gluteus maximus bursa: computed tomography and magnetic resonance imaging findings

Chondral tumors in soft tissue are referred to as soft-tissue chondromas or extraskeletal chondromas, or as synovial chondromatosis if they arise in synovial tissue. We report the case of a 29-year-old man with synovial chondromatosis, also called synovial osteochondromatosis, which appeared in a solitary and extra-articular form. On magnetic resonance imaging (MRI) and computed tomography, the central portion of the tumor showed similar characteristics to bone marrow, despite the absence of any connection to adjacent bone. T2-weighted imaging displayed marked peripheral hyperintensity consistent with a cartilaginous area. These findings suggested the presence of enchondral ossification and were similar to those of skeletal osteochondroma, with the exception of the absence of attachment to bone. MRI is useful for distinguishing solitary synovial chondromatosis from other lesions, such as myositis ossificans, extraskeletal chondrosarcoma, and parosteal osteosarcoma.

Cell cycle deregulation and mosaic loss of Ext1 drive peripheral chondrosarcomagenesis in the mouse and reveal an intrinsic cilia deficiency

Peripheral chondrosarcoma (PCS) develops as malignant transformation of an osteochondroma, a benign cartilaginous outgrowth at the bone surface. Its invasive, lobular growth despite low-grade histology suggests a loss of chondrocyte polarity. The known genetics of osteochondromagenesis include mosaic loss of EXT1 or EXT2 in both hereditary and non-hereditary cases. The most frequent genetic aberrations in human PCS also include disruptions of CDKN2A or TP53. In order to test the sufficiency of either of these to drive progression of an osteochondroma to PCS, we added conditional loss of Trp53 or Ink4a/Arf in an Ext1-driven mouse model of osteochondromagenesis. Each additional tumour suppressor silencing efficiently drove the development of growths that mimic human PCS. As in humans, lobules developed from both Ext1-null and Ext1-functional clones within osteochondromas. Assessment of their orientation revealed an absence of primary cilia in the majority of mouse PCS chondrocytes, which was corroborated in human PCSs. Loss of primary cilia may be responsible for the lost polarity phenotype ascribed to PCS. Cilia deficiency blocks proliferation in physeal chondrocytes, but cell cycle deregulation is sufficient to rescue chondrocyte proliferation following deciliation. This provides a basis of selective pressure for the frequent cell-cycle regulator silencing observed in peripheral chondrosarcomagenesis. Mosaic loss of Ext1 combined with loss of cell cycle regulators promotes peripheral chondrosarcomagenesis in the mouse and reveals deficient ciliogenesis in both the model and the human disease, explaining biological behaviour including lobular and invasive growth.