EXT-related pathways are not involved in the pathogenesis of dysplasia epiphysealis hemimelica and metachondromatosis

Multiple Distal Femoral Osteochondromas Encasing Popliteal Neurovascular Bundle

Multiple hereditary exostosis syndrome is a rare diagnosis with approximately 1:50000 incidence prevailing in males. The exostoses or osteochondromas are benign but have the potential for malignant transformation in 1-5%. There is a strong genetic component, with exostosis (EXT) signaling pathways being an underlying cause. They can be symptomatic, with pain and functional deficit as the main complaints. We present a case of a 17-year-old male who presented with pain and anatomical deformity in his left lower femur. Magnetic resonance imaging revealed multiple osteochondromas compressing the popliteal neurovascular bundle. Excision of the osteochondromas was performed to decompress the neurovascular bundle in a multidisciplinary approach. Histological examination demonstrated no evidence of malignancy. Currently, there is no consensus for patients diagnosed with multiple osteochondromas regarding further investigation and/or screening for malignant transformation.

Hemimelic epiphyseal dysplasia: a case report

Hemimelic epiphyseal dysplasia HED also known as Trevor's disease is a rare pathology, characterized by a developmental disorder of an internal or external half of one or more epiphyses of a limb, mainly the lower limb, and/or of the short tarsal bones in children and young adolescents, with a male predominance. Its etiology remains unclear. Its clinical symptomatology is variable, ranging from asymptomatic involvement to orthopedic complications such as limb length inequality. As the clinic is non-specific, radiological assessment is the essential diagnostic tool for Trevor's disease, including standard radiography, MRI, CT, and possibly biopsy in some cases. The radio clinical signs make it possible to establish the diagnosis, even if it remains difficult because of the rarity of the disease and the presence of multiple differential diagnoses which are often better known such as osteochondroma and exostosis. After diagnostic confirmation, the therapeutic decision remains debated, ranging from simple observation to surgical excision. The prognosis of HED remains good, given the absence of the risk of malignant transformation. Post-therapeutic complications are dominated by recurrence or the appearance of secondary osteoarthritis. Objective: This clinical case challenges us to keep in mind the hemimelic epiphyseal dysplasia (HED) in front of a mass that originates at the level of the internal or external half of one or more epiphyses in children.

Treatment of Dysplasia Epiphysealis Hemimelica with Autologous Chondrocyte Implantation: A Case Report

CASE

We present a case of dysplasia epiphysealis hemimelica (DEH) involving the posteromedial distal femur in a 4-year-old girl. The patient underwent lesion resection with internal fixation of the articular cartilage followed by autologous chondrocyte implantation (ACI) to restore the articular surface and epiphysis. At the 7-year follow-up, the patient had no pain or difficulty with participation in sports. Advanced imaging showed a stable articular surface with evidence of durable cartilage integration.

CONCLUSION

DEH is a rare disease often treated by resection. In cases where the articular surface of the knee is involved, we have demonstrated that augmentation with ACI can be an effective treatment option.

Dysplasia Epiphysealis Hemimelica (Trevor's Disease) in Children, Two New Cases: Diagnosis, Treatment, and Literature Review

Dysplasia epiphysealis hemimelica (DEH), also known as Trevor’s disease, is a rare nonhereditary skeletal disorder affecting one side of the epiphyses or the epiphyses-equivalents. It is often misdiagnosed for traumatic injuries, infections, or other tumors because of the nonspecific clinical features. The diagnosis is mostly based on radiographic involvement of one half of the epiphysis displaying an overgrowth; it is hard to distinguish between DEH and osteochondroma on the gross hystopathological exam. There are few immunohistochemical markers, as well as genetic tests, for EXT1 and EXT2 gene expression that can reveal a more accurate diagnosis. No evidence of malignant changes has been reported and no hereditary transmission or environmental factor has been incriminated as an etiological factor. The natural history of the disease is continuous growth of the lesions until skeletal maturity. Without treatment, the joint might suffer degenerative modification, and the patient can develop early onset osteoarthritis. In the present paper, we report two new cases of DEH of the ankle. The aim of this paper is to consider Trevor’s disease when encountering tumoral masses in the epiphyses of pediatric patients and to present our treatment approach and results.

Dysplasia Epiphysealis Hemimelica (Trevor Disease) of the Patella: A Case Report

CASE

We report a rare case of dysplasia epiphysealis hemimelica in an 11-year-old male child involving the patella. The patient noticed swelling in the right knee 6 months before presentation. On evaluation, there was a mass lesion originating from superior pole of the patella extending into the suprapatellar pouch. On opening the knee joint, it was found to be mainly cartilaginous in nature. Surgical excision of the mass was carried out.

CONCLUSION

Trevor disease should be considered in the differential diagnosis of a mass originating from the patella in children. The recommended treatment is complete excision of the mass.

Juvenile Dysplasia Epiphysealis Hemimelica with Multiple Ankle Free Body

Dysplasia epiphysealis hemimelica (DEH), also known as Trevor's disease, is a rare overgrowth of cartilage that commonly arises in the epiphyseal bone of children. We report a rare case of DEH originating from a talus accompanied by multiple intra-articular free bodies in a 7-year-old patient with ankle instability. After the primary surgery for free body removal and microfracture technique for the cartilage defects in the ankle joint, the free body recurred. Secondary surgery of arthroscopic free body removal with lateral ankle ligament repair succeeded in treating the patient, without further recurrence of the free body.

FAM172A promotes follicular thyroid carcinogenesis and may be a marker of FTC

Our aims were to uncover the role of FAM172A (Family with sequence similarity 172 member A) in the pathogenesis of follicular thyroid carcinoma (FTC) and to evaluate its value in the differential diagnosis between malignant and benign thyroid follicular lesions. FAM172A expression was evaluated by q-PCR, immunoblotting and immunohistochemistry (IHC). The ability of proliferation, migration and invasion of cells were assessed by Cell Counting Kit-8 assay (CCK8), clone-formation and Transwell assays. Nude mouse tumorigenicity assays were used to investigate the role of FAM172A in the pathogenesis of FTC in vivo. The value of FAM172A in the differential diagnosis for FTC was assessed using 120 formalin-fixed paraffin-embedded (FFPE) tissues after the operation and 81 fine-needle aspiration biopsy (FNAB) samples before the operation. FAM172A was highly expressed in FTC tissues and FTC cell lines. Downregulation of FAM172A inhibited the proliferation, invasion and migration of FTC cells through Erk1/2 and JNK pathways. Subcutaneous tumorigenesis in nude mice showed that knockdown of FAM172A inhibited tumor growth and progression in vivo. The FAM172A IHC scores of 3.5 had 92% sensitivity and 63% specificity to separate FTC from benign/borderline thyroid follicular lesions, and 92% sensitivity and 80% specificity to discriminate FTC from benign thyroid follicular lesions in postoperative FFPE samples. The corresponding values were 75 and 78%, and 75 and 89% in preoperative FNA samples, respectively. FAM172A plays an important role in the pathogenesis of FTC through Erk1/2 and JNK pathways. FAM172A may be a potential marker for the preoperative diagnosis of FTC based on the IHC results of thyroid FNAB samples.

Dysplasia epiphysealis hemimelica combined with contralateral accessory scaphoid bone: A case report and literature review

RATIONALE

Dysplasia epiphysealis hemimelica (DEH), also known as Trevor disease, is a rare, developmental bone disorder of childhood.

PATIENT CONCERNS

A 9-year-old girl was admitted due to pain in front of the medial malleolus of her right foot after a long walk or distance movement, in which the pain could be relieved after rest, while it was repeated and lasted for several months.

DIAGNOSIS

Dysplasia epiphysealis hemimelica INTERVENTIONS:: The patient underwent an open resection surgery. After operation, the pain was totally relieved. Postoperative pathological diagnosis showed DEH.

OUTCOMES

At the 6-month follow-up, pain and claudication symptoms fully disappeared, and range of motion of the right foot returned to normal level.

CONCLUSIONS

Dysplasia epiphysealis hemimelica is an uncommon disease which can cause pain of foot in children.

LESSONS

When the pediatric orthopedic surgeon treated the children suffered with foot pain should be aware of this rare disease, especially accessory scaphoid bone was found in another foot.

Asymptomatic Dysplasia Epiphysealis Hemimelica of the Shoulder in a Skeletally Mature Patient with Normal Function

Dysplasia epiphysealis hemimelica is a rare osteocartilaginous overgrowth syndrome of bone epiphysis, mostly encountered in the lower limbs of immature skeleton patients. We report a case of proximal humerus presentation in an adult male, with neither articular involvement nor clinical dysfunction. This case highlights the importance of stratification into intra- and extra-articular lesions, as this distinction ultimately influences both symptoms and treatment outcome. In addition, the case highlights the importance of specific imaging modalities, such as CT and MR images, which provide excellent anatomic location of the lesion, adequate extension of cartilaginous components, exact status of articular cartilage, and accurate assessment of neighboring structures, such as vessels, nerves, ligaments, tendons, and muscles. The imaging features are described, the relevant literature is reviewed, and salient features are discussed.

Multiple unexpected lesions of metachondromatosis detected by technetium-99m methylene diphosphonate SPECT/CT: A case report

RATIONALE

Metachondromatosis (MC) is a very rare genetic disease, which is infrequently reported worldwide, which leads to osteochondroma and enchondromatosis. The disease has been shown to be associated with loss of function of the tumor suppressor gene "protein tyrosine phosphatase, non-receptor type 11" (PTPN11).

PATIENT CONCERNS

A 12-year-old female was admitted to the hospital with pain due to an enlarged mass in her left fifth finger.

DIAGNOSIS

Examination of the left hand by computed tomography (CT) revealed an expanding type of round and low-density lesion in the fifth proximal phalanx. The patient then underwent technetium-99m methylene diphosphonate single-photon emission CT/CT (Tc-MDP SPECT/CT) to assess the nature of the lesion. The SPECT/CT image revealed dilated osteopathy and increased activity of the fifth proximal phalanx on the left hand. Unexpectedly, the examination of the right hand revealed slight expanded lesions and increased activities of the third metacarpal and proximal phalange, as well as the fourth proximal phalange and the middle phalanx. On the basis of the patient's symptoms and the results of the above-mentioned examinations, we diagnosed the patient as having MC in her hands.

INTERVENTION

Considering the pain of the fifth finger of the left hand, the patient underwent debridement of the fifth proximal phalanx of the left hand and internal fixation with bone graft taken from the body.

OUTCOMES

The patient was discharged after a week of observation. One year later, she was admitted to the hospital again for removal of the bone healing internal fixation after osteoma surgery. Preoperative Tc-MDP SPECT/CT revealed that the left-handed lesions displayed postoperative changes, while the multiple lesions in the right hand increased in volume but remained unchanged in number.

LESSONS

This case revealed the CT and Tc-MDP SPECT/CT imaging features of MC. Specifically, SPECT/CT imaging contributed to the diagnosis of clinically asymptomatic bone lesions, and the 3D SPECT/CT fusion allowed a more comprehensive and intuitive view of the lesion by combining anatomy and function.

Dysplasia epiphysealis hemimelica: a histological comparative study with osteochondromas

PURPOSE

Dysplasia epiphysealis hemimelica (DEH) is a rare developmental disorder resulting in epiphyseal overgrowth. Based on histological appearance, it is often described as an osteochondroma or osteochondroma-like lesion, although clinical differences exist between DEH and osteochondromas. The aim of this study was to test whether DEH and osteochondromas are histologically identical diseases.

METHODS

Tissue samples of two age- and gender-matched cases with DEH and hereditary multiple exostoses were histologically compared. Sections were stained with Safranin-O for detection of proteoglycans and immunohistochemistry was performed for detection of collagen type II, collagen type X as a marker of hypertrophic chondrocytes and Sox9 as a marker of proliferative chondrocytes. Due to the rarity, descriptions of the included DEH patients were outlined.

RESULTS

Histologically, chondrocyte clusters in a fibrillary matrix, a thick disorganised cartilage cap and ossification centres with small amounts of unabsorbed cartilage, were observed in DEH. In contrast, cartilage organisation of osteochondromas displays characteristics of the normal growth plate. Collagen type II was clearly detected in the cartilaginous extracellular matrix in osteochondromas, while weak expression was observed in DEH. Collagen type X was not detected in DEH, while expressed in the matrix surrounding hypertrophic chondrocytes in osteochondromas. Sox9 staining was positive in hypertrophic chondrocytes in osteochondromas, while expressed in nuclei of chondrocyte clusters in DEH.

CONCLUSION

Both morphological and immunohistological differences were observed in histological sections of DEH and osteochondromas. These results support the previously identified clinical, radiological and genetic differences and imply a different aetiology between DEH and osteochondroma formation.

Arthroscopic Treatment of 2 Consecutive Cases of Dysplasia Epiphysealis Hemimelica of the Ankle: A 5-Year Follow-Up Report

The dysplasia epiphysealis hemimelica (DEH) is a rare disease of unknown etiology consisting in an abnormal osteocartilaginous growth at the epiphysis, usually hemimelic with histological findings similar to benign osteochondroma. In this case series, we described the results of the arthroscopic treatment of 2 consecutive cases of intra-articular ankle localization of DEH in 2 patients aged 9 and 10 years. The good result obtained, persistent at the 5-year follow-up, leads us to consider the arthroscopic approach as a reliable treatment in patient affected by intra-articular ankle DEH.

Dysplasia epiphysealis hemimelica of the lower limb

Dysplasia epiphysealis hemimelica (DEH) is a rare developmental disorder characterized by osteocartilaginous overgrowth in one or more epiphyses. The disease usually involves a single limb or is hemimelic (lateral or medial compartment), and lower extremities are more frequently affected than upper extremities. Here we present clinical and radiological findings for a male DEH patient at 1.5 and 3.5 years of age. The radiographs obtained at first presentation showed minimal osseous overgrowth and irregularity at the epiphyses around the left knee and ankle joints, respectively. Radiographs obtained at the second presentation showed osteocartilaginous masses at most epiphyses of the left lower extremity. Two months after diagnosis (at 3.7 years old), the patient had surgery on his left knee to relieve increased joint restriction. The histopathological diagnosis was consistent with an osteocartilaginous lesion. This case report presents imaging features and age-related progression of DEH in this patient.

Multidetector computed tomography in the evaluation of hereditary multiple exostoses

Hereditary multiple exostoses (HME) is an autosomal dominant disorder characterized by the formation of multiple osteochondromas. Because of its superior soft tissue contrast and absence of ionizing radiation, magnetic resonance imaging is the first choice imaging technique for the evaluation of complex lesions and complications related to HME. However, multidetector computed tomography (MDCT) also can be of value in the evaluation of patients with HME, which is reviewed in this article. Topics outlined are low-dose MDCT technique, 3-dimensional visualization techniques, typical MDCT appearances, differential diagnostic considerations, and the usefulness of MDCT in the assessment of emergent and non-emergent complications related to HME, among which spinal cord compression, pneumothorax and hematothorax, pseudoaneurysms, fractures, growth disturbances, chondrosarcoma transformation, and muscular and peripheral nerve involvement.

Intraosseous atypical chondroid tumor or chondrosarcoma grade 1 in patients with multiple osteochondromas

BACKGROUND

The autosomal dominant condition multiple osteochondromas, formerly called multiple hereditary exostoses, is associated with a risk of malignant progression of osteochondroma into secondary peripheral chondrosarcoma. Most patients with multiple osteochondromas have exostosin-1 or exostosin-2 gene mutations. To our knowledge, it has not been previously reported that patients may also harbor intraosseous (central) chondroid neoplasms, enchondromas, or atypical chondroid tumors or central chondrosarcomas. The combination of osteochondroma and enchondromas also exists in patients with metachondromatosis, a disorder associated with a protein tyrosine phosphatase non-receptor type 11 gene mutation. This study aims to establish any correlation between multiple osteochondromas and intraosseous cartilaginous neoplasms.

METHODS

We retrospectively reviewed all histologically proven intraosseous atypical chondroid tumors or chondrosarcomas in our prospective nationwide Dutch tertiary referral multiple osteochondromas database. Demographic, clinical, radiographic, histological, and genetic data were recorded. The institutional medical ethics review board approved the study.

RESULTS

From 195 adult patients, seven (3.6%) were identified with intraosseous atypical chondroid tumor or chondrosarcoma World Health Organization grade 1 and had a mean age of forty-two years; five of these patients were male. In all cases, radiographic and genetic findings were consistent with multiple osteochondromas, not metachondromatosis; three patients had an exostosin-1 mutation, four patients had an exostosin-2 mutation, and no patients had a protein tyrosine phosphatase, non-receptor type 11 mutation. Six patients underwent successful operative treatment without complications or recurrences after a mean follow-up duration of forty-eight months (range, twelve to 144 months). One patient was scheduled for surgery after biopsy and histologic confirmation. Of the seven patients, five (71%) also developed a peripheral chondrosarcoma in a known osteochondroma during the study period.

CONCLUSIONS

Apart from osteochondromas or peripheral chondrosarcomas, multiple osteochondromas are also associated with intraosseous chondroid neoplasms, potentially resulting in central chondrosarcoma. Therefore, intraosseous lesions should not automatically be regarded as innocuous in this patient population.

Metachondromatosis: more than just multiple osteochondromas

INTRODUCTION

Metachondromatosis is a rare genetic disease of osteochondroma and enchondroma formation, caused by loss of function of the PTPN11 gene. It is distinct from other similar conditions such as multiple osteochondromas and hereditary multiple exostoses by the distribution and orientation of lesions, and pattern of inheritance. Lesions typically occur in hands, feet, femora, tibiae and the pelvis. Lesions are typically reported to regress in adulthood.

METHODS

We reviewed the current literature on metachondromatosis, and present four new cases in a family with metachondromatosis.

RESULTS

Long-term follow up data reveal spontaneous regression of lesions by skeletal maturity. Complications may include nerve palsy due to the mass effect of lesions, avascular necrosis of the femoral head and angular deformity of long bones. Histopathological analysis has demonstrated that lesions in metachondromatosis are a mix of osteochondromas and enchondromas; however, one case of chondrosarcoma has been reported.

CONCLUSION

Lesions associated with metachondromatosis may cause a variety of complications due to mass effects; however, they are often asymptomatic, cause cosmetic concerns and, importantly, most regress spontaneously. Regular clinical review with selective imaging to monitor for such complications is appropriate, but uncomplicated lesions are unlikely to require surgical intervention.

Imaging of dysplasia epiphysealis hemimelica (Trevor's disease)

Dysplasia epiphysealis hemimelica (DEH; synonyms; Trevor's or Trevor Fairbank disease) is a rare developmental disorder of the skeleton characterized by asymmetric osteochondral overgrowth of the cartilage of a medial or lateral epiphysis or epiphyseal equivalent. Imaging plays an important role in the diagnosis and management of DEH and in assessing the need for biopsy to differentiate it from more sinister diseases. There is no recent comprehensive review of the imaging of DEH and the purpose of this article is to describe the modern radiological manifestations of DEH.

EXT2-positive multiple hereditary osteochondromas with some features suggestive of metachondromatosis

Metachondromatosis (MC) and hereditary multiple osteochondromas (HMO) are thought to be distinct disorders, each with characteristic x-ray and clinical features. Radiographic differences are the current mainstay of differential diagnosis. Both disorders are autosomal dominant, but the majority of patients with HMO have mutations in EXT-1 or EXT 2 genes. The genetic defect in MC is unknown, although recent studies indicate a possible identifiable mutation. The cancer risk in HMO is thought to be greater than in MC, although the small number of cases make such conjecture imprecise. The purpose of this report is to review existing literature and examine whether radiographic findings in HMO and MC can be reliable as a stand-alone means of differential diagnosis. Three members of a multi-generational family with an autosomal dominant exostosis syndrome were studied by clinical examination and complete skeletal survey. The roentgenographic characteristics of all osteochondromas were analyzed. The father underwent gene sequencing for EXT-1 and EXT-2, which revealed a novel EXT-2 mutation. Typical radiographic and clinical findings of both HMO and MC were seen throughout the family as well as in individuals. These family study findings contradict many of the long-standing clinical and x-ray diagnostic criteria for differentiating MC from HMO. The phenotypic crossover between the two conditions in this family, and results of genetic analysis, suggest that in the absence of a definitive genetic diagnosis, radiographic and clinical diagnosis of past and future cases HMO and MC may not be as reliable as previously assumed.

Loss-of-function mutations in PTPN11 cause metachondromatosis, but not Ollier disease or Maffucci syndrome

Metachondromatosis (MC) is a rare, autosomal dominant, incompletely penetrant combined exostosis and enchondromatosis tumor syndrome. MC is clinically distinct from other multiple exostosis or multiple enchondromatosis syndromes and is unlinked to EXT1 and EXT2, the genes responsible for autosomal dominant multiple osteochondromas (MO). To identify a gene for MC, we performed linkage analysis with high-density SNP arrays in a single family, used a targeted array to capture exons and promoter sequences from the linked interval in 16 participants from 11 MC families, and sequenced the captured DNA using high-throughput parallel sequencing technologies. DNA capture and parallel sequencing identified heterozygous putative loss-of-function mutations in PTPN11 in 4 of the 11 families. Sanger sequence analysis of PTPN11 coding regions in a total of 17 MC families identified mutations in 10 of them (5 frameshift, 2 nonsense, and 3 splice-site mutations). Copy number analysis of sequencing reads from a second targeted capture that included the entire PTPN11 gene identified an additional family with a 15 kb deletion spanning exon 7 of PTPN11. Microdissected MC lesions from two patients with PTPN11 mutations demonstrated loss-of-heterozygosity for the wild-type allele. We next sequenced PTPN11 in DNA samples from 54 patients with the multiple enchondromatosis disorders Ollier disease or Maffucci syndrome, but found no coding sequence PTPN11 mutations. We conclude that heterozygous loss-of-function mutations in PTPN11 are a frequent cause of MC, that lesions in patients with MC appear to arise following a “second hit,” that MC may be locus heterogeneous since 1 familial and 5 sporadically occurring cases lacked obvious disease-causing PTPN11 mutations, and that PTPN11 mutations are not a common cause of Ollier disease or Maffucci syndrome.

Children with cartilage tumor syndromes form multiple tumors of cartilage next to joints. These tumors can occur inside the bones, as with Ollier disease and Maffuci syndrome, or on the surface of bones, as in the Multiple Osteochondroma syndrome (MO). In a hybrid syndrome, called metachondromatosis (MC), patients develop tumors both on and within bones. Only the genes causing MO are known. Since MC is inherited, we studied genetic markers in an affected family and found a region of the genome, encompassing 100 genes, always passed on to affected members. Using a recently developed method, we captured and sequenced all 100 genes in multiple families and found mutations in one gene, PTPN11, in 11 of 17 families. Patients with MC have one mutant copy of PTPN11 from their affected parent and one normal copy from their unaffected parent in all cells. We found that the normal copy is additionally lost in cartilage cells that form tumors, giving rise to cells without PTPN11. Mutations in PTPN11 were not found in other cartilage tumor syndromes, including Ollier disease and Maffucci syndrome. We are currently working to understand how loss of PTPN11 in cartilage cells causes tumors to form.

Whole-genome sequencing of a single proband together with linkage analysis identifies a Mendelian disease gene

Although more than 2,400 genes have been shown to contain variants that cause Mendelian disease, there are still several thousand such diseases yet to be molecularly defined. The ability of new whole-genome sequencing technologies to rapidly indentify most of the genetic variants in any given genome opens an exciting opportunity to identify these disease genes. Here we sequenced the whole genome of a single patient with the dominant Mendelian disease, metachondromatosis (OMIM 156250), and used partial linkage data from her small family to focus our search for the responsible variant. In the proband, we identified an 11 bp deletion in exon four of PTPN11, which alters frame, results in premature translation termination, and co-segregates with the phenotype. In a second metachondromatosis family, we confirmed our result by identifying a nonsense mutation in exon 4 of PTPN11 that also co-segregates with the phenotype. Sequencing PTPN11 exon 4 in 469 controls showed no such protein truncating variants, supporting the pathogenicity of these two mutations. This combination of a new technology and a classical genetic approach provides a powerful strategy to discover the genes responsible for unexplained Mendelian disorders.

Dysplasia epiphysealis hemimelica: a case report with novel pathophysiologic aspects

Dysplasia epiphysealis hemimelica (DEH) is a rare developmental disorder. The underlying pathophysiology is largely unclear. Its diagnosis is based on clinical findings and may be difficult due to its low incidence and close relationship to other disorders such as osteochondroma. We describe a 13-year-old boy who presented with a unilateral lesion of the left medial femoral condyle and left ankle. In addition to standard diagnostic tools such as radiographs and MRI, arthroscopy-guided biopsy was performed; histologic/immunohistochemical findings from cartilage-bone specimens confirmed the diagnosis and provided novel information toward a disease mechanism. The cellular phenotype of clustered chondrocytes exhibited characteristics of chondroprogenitor cells and terminally differentiated cells, suggesting dysregulation of resident progenitor cells. No other surgery was performed and during a 2 year period, we observed spontaneous ossification of the lesion associated with decreased joint impairment. Immunohistochemical analysis of the lesion provided a more accurate diagnosis and may contribute to unraveling potential novel mechanisms involved in its pathogenesis.

Benign cartilaginous tumors of bone: from morphology to somatic and germ-line genetics

Benign cartilaginous tumors of bones, intrinsic to their name, are tumors forming cartilaginous matrix with a clinically benign behavior. In this group, we recognize osteochondromas, (en)chondromas, chondroblastomas, and chondromyxoid fibromas. This group includes common tumors, that is, osteochondroma and (en)chondroma as well as rare tumors such as chondroblastoma and chondromyxoid fibroma. Several benign and malignant tumors may mimic benign cartilaginous tumors of bones. We reviewed the main morphologic features and the differential diagnosis is discussed. The genetics of these tumors is intriguing ranging from single gene event (ie, EXT mutation in multiple osteochondromas) to heterogeneous rearrangements with no recurrent involved chromosomal regions such as in chondroblastoma. The main genetic findings are hereby reviewed.

Generalized dysplasia epiphysealis hemimelica with contralateral sacro-iliac joint involvement

Dysplasia epiphysealis hemimelica (or Trevor's disease) is a rare developmental bone dysplasia characterized by benign osteocartilaginous overgrowth involving one or multiple epiphyses, usually of a single lower extremity. It is classified as localized form, classical form (most common), and generalized form. In this report we describe a case of generalized form of dysplasia epiphysealis hemimelica with involvement of the contralateral sacroiliac joint, which is an extremely rare presentation.

Multiple osteochondromas

Multiple osteochondromas (MO) is characterised by development of two or more cartilage capped bony outgrowths (osteochondromas) of the long bones. The prevalence is estimated at 1:50,000, and it seems to be higher in males (male-to-female ratio 1.5:1). Osteochondromas develop and increase in size in the first decade of life, ceasing to grow when the growth plates close at puberty. They are pedunculated or sessile (broad base) and can vary widely in size. The number of osteochondromas may vary significantly within and between families, the mean number of locations is 15-18. The majority are asymptomatic and located in bones that develop from cartilage, especially the long bones of the extremities, predominantly around the knee. The facial bones are not affected. Osteochondromas may cause pain, functional problems and deformities, especially of the forearm, that may be reason for surgical removal. The most important complication is malignant transformation of osteochondroma towards secondary peripheral chondrosarcoma, which is estimated to occur in 0.5-5%. MO is an autosomal dominant disorder and is genetically heterogeneous. In almost 90% of MO patients germline mutations in the tumour suppressor genes EXT1 or EXT2 are found. The EXT genes encode glycosyltransferases, catalyzing heparan sulphate polymerization. The diagnosis is based on radiological and clinical documentation, supplemented with, if available, histological evaluation of osteochondromas. If the exact mutation is known antenatal diagnosis is technically possible. MO should be distinguished from metachondromatosis, dysplasia epiphysealis hemimelica and Ollier disease. Osteochondromas are benign lesions and do not affect life expectancy. Management includes removal of osteochondromas when they give complaints. Removed osteochondromas should be examined for malignant transformation towards secondary peripheral chondrosarcoma. Patients should be well instructed and regular follow-up for early detection of malignancy seems justified. For secondary peripheral chondrosarcoma, en-bloc resection of the lesion and its pseudocapsule with tumour-free margins, preferably in a bone tumour referral centre, should be performed.

Dysplasia epiphysealis hemimelica (Trevor disease): a rare developmental disorder of bone mimicking osteochondroma of long bones

Dysplasia epiphysealis hemimelica (DEH) is a rare developmental disorder of childhood and is characterized by asymmetric enlargement of the epiphyseal cartilage of the long bones. After 4 to 5 years of age, the lesions histologically resemble osteochondroma. To our knowledge, only one publication of this entity is available in an English pathology journal. The clinical, radiographic, and histologic features of 9 cases of DEH were retrospectively reviewed. The patients' age ranged from 3 to 15 years with single or multiple lesions of the femur, fibula, tibia, and talus. The etiology and pathogenesis of DEH are not known. Its origin and evolution has initially apparent similarities to the development and growth of epiphyseal secondary ossification centers. DEH can be differentiated from osteochondroma of long bones using clinical, radiologic, and pathologic parameters. DEH occurs in young children and adolescents manifesting as lesions that arise particularly from the epiphysis of the lower extremities and tarsus. Osteochondroma, in contrast, occurs most frequently between 10 and 30 years of age and originates from the metaphysis of long bones. Although the DEH cartilage resembles osteochondroma, there are several significant histologic differences. During infancy, lesions of DEH histologically reveal osteocartilaginous nodules that resemble secondary ossification centers. Usually after 4 to 5 years of age they develop into osteochondroma-like lesions. Although all cases of DEH contain small areas of calcified cartilage beneath the cartilage cap, a significant percentage of osteochondromas show large amounts. The nodules and cartilage cap of DEH contain bands of cartilage separating areas of cancellous bone; these bands are not present in osteochondroma. Among the other distinguishable features, recent molecular studies of DEH demonstrated normal expression levels of EXT1 and EXT2 genes, comparable to that of normal growth plate. Osteochondroma, in contrast, has low levels of EXT1 and EXT2 gene expression due to gene mutation. The histologic differences in combination with the distinct clinical and radiographic features should enable a pathologist to differentiate these entities.