[Osteochondroma and multiple osteochondromas: recommendations on the diagnostics and follow-up with special consideration to the occurrence of secondary chondrosarcoma]

A retrospective external validation study of the Birmingham Atypical Cartilage Tumour Imaging Protocol (BACTIP) for the management of solitary central cartilage tumours of the proximal humerus and around the knee

OBJECTIVES

This study aimed to externally validate the Birmingham Atypical Cartilage Tumour Imaging Protocol (BACTIP) recommendations for differentiation/follow-up of central cartilage tumours (CCTs) of the proximal humerus, distal femur, and proximal tibia and to propose BACTIP adaptations if the results provide new insights.

METHODS

MRIs of 123 patients (45 ± 11 years, 37 men) with an untreated CCT with MRI follow-up (n = 62) or histopathological confirmation (n = 61) were retrospectively/consecutively included and categorised following the BACTIP (2003-2020 / Ghent University Hospital/Belgium). Tumour length and endosteal scalloping differences between enchondroma, atypical cartilaginous tumour (ACT), and high-grade chondrosarcoma (CS II/III/dedifferentiated) were evaluated. ROC-curve analysis for differentiating benign from malignant CCTs and for evaluating the BACTIP was performed.

RESULTS

For lesion length and endosteal scalloping, ROC-AUCs were poor and fair-excellent, respectively, for differentiating different CCT groups (0.59-0.69 versus 0.73-0.91). The diagnostic performance of endosteal scalloping and the BACTIP was higher than that of lesion length. A 1° endosteal scalloping cut-off differentiated enchondroma from ACT + high-grade chondrosarcoma with a sensitivity of 90%, reducing the potential diagnostic delay. However, the specificity was 29%, inducing overmedicalisation (excessive follow-up). ROC-AUC of the BACTIP was poor for differentiating enchondroma from ACT (ROC-AUC = 0.69; 95%CI = 0.51-0.87; p = 0.041) and fair-good for differentiation between other CCT groups (ROC-AUC = 0.72-0.81). BACTIP recommendations were incorrect/unsafe in five ACTs and one CSII, potentially inducing diagnostic delay. Eleven enchondromas received unnecessary referrals/follow-up.

CONCLUSION

Although promising as a useful tool for management/follow-up of CCTs of the proximal humerus, distal femur, and proximal tibia, five ACTs and one chondrosarcoma grade II were discharged, potentially inducing diagnostic delay, which could be reduced by adapting BACTIP cut-off values.

CLINICAL RELEVANCE STATEMENT

Mostly, Birmingham Atypical Cartilage Tumour Imaging Protocol (BACTIP) assesses central cartilage tumours of the proximal humerus and the knee correctly. Both when using the BACTIP and when adapting cut-offs, caution should be taken for the trade-off between underdiagnosis/potential diagnostic delay in chondrosarcomas and overmedicalisation in enchondromas.

KEY POINTS

• This retrospective external validation confirms the Birmingham Atypical Cartilage Tumour Imaging Protocol as a useful tool for initial assessment and follow-up recommendation of central cartilage tumours in the proximal humerus and around the knee in the majority of cases. • Using only the Birmingham Atypical Cartilage Tumour Imaging Protocol, both atypical cartilaginous tumours and high-grade chondrosarcomas (grade II, grade III, and dedifferentiated chondrosarcomas) can be misdiagnosed, excluding them from specialist referral and further follow-up, thus creating a potential risk of delayed diagnosis and worse prognosis. • Adapted cut-offs to maximise detection of atypical cartilaginous tumours and high-grade chondrosarcomas, minimise underdiagnosis and reduce potential diagnostic delay in malignant tumours but increase unnecessary referral and follow-up of benign tumours.

The identification of a novel frameshift insertion mutation in the EXT1 gene in a Chinese family with hereditary multiple exostoses

To identify the pathogenic gene variation in a Chinese family with Hereditary Multiple Exostoses (HME). By examining blood‐sourced DNA and clinical manifestations of the proband and his family members, the whole exome sequencing (WES) and Sanger sequencing were used to detect possibly pathogenic mutations. A novel heterozygous mutation (c.325dup) was identified in exon 1 of the exostosin 1 (EXT1) gene from the proband and the affected family members. And we found this mutation was absent in all the unaffected family members. This c.325dup mutation is in the exon 1 domain of the EXT1 gene and the change of p.C109Lfs*80 cause the early termination of protein translation. The identification of the novel frameshift insertion mutation (c.325dup) expands the mutation spectrum of HME, which provides new evidence for HME diagnosis.

Hereditary Multiple Exostoses-A Review of the Molecular Background, Diagnostics, and Potential Therapeutic Strategies

Hereditary multiple exostoses (HMEs) syndrome, also known as multiple osteochondromas, represents a rare and severe human skeletal disorder. The disease is characterized by multiple benign cartilage-capped bony outgrowths, termed exostoses or osteochondromas, that locate most commonly in the juxta-epiphyseal portions of long bones. Affected individuals usually complain of persistent pain caused by the pressure on neighboring tissues, disturbance of blood circulation, or rarely by spinal cord compression. However, the most severe complication of this condition is malignant transformation into chondrosarcoma, occurring in up to 3.9% of HMEs patients. The disease results mainly from heterozygous loss-of-function alterations in the EXT1 or EXT2 genes, encoding Golgi-associated glycosyltransferases, responsible for heparan sulfate biosynthesis. Some of the patients with HMEs do not carry pathogenic variants in those genes, hence the presence of somatic mutations, deep intronic variants, or another genes/loci is suggested. This review presents the systematic analysis of current cellular and molecular concepts of HMEs along with clinical characteristics, clinical and molecular diagnostic methods, differential diagnosis, and potential treatment options.

An update on the imaging of diaphyseal aclasis

Solitary osteochondromas are common, benign hyaline cartilage-capped exostoses that primarily arise from the metaphyses of long and flat bones. Diaphyseal aclasis is an autosomal dominant condition resulting from EXT1 or EXT2 gene mutations and is characterized by multifocal osteochondromas. These can result in a wide spectrum of complications, such as skeletal deformity, neurological and vascular complications, adventitial bursa formation, fracture, and rarely malignant transformation to peripheral chondrosarcoma. In this review, we outline in detail the multimodality imaging features of DA and its associated complications.

The Epidemiology of Benign Proliferative Processes of the Skeletal System in Children

A suspicion of a proliferative bone lesion in a child seems to be a major diagnostic problem for clinicians. There are no diagnostic and treatment algorithms described in the literature and no reliable cohort epidemiological data. Our study was conducted among 289 paediatric patients (0–18 years old) with an initial diagnosis of a bone tumour or tumour-like lesion. The study comprised a retrospective epidemiological analysis, an assessment of the concordance of the initial diagnoses with the histopathological diagnoses and an analysis of the specific locations of the various bone lesions. The results obtained have made it possible to formulate the following conclusions. (1) The most common proliferative bone lesion in children is osteochondroma; also common are fibrous dysplasia, non-ossifying fibromas and bone cysts. (2) Verifying the initial diagnosis by means of biopsy is essential. (3) Osteochondromas are typically located in the metaphyses of long bones, fibrous dysplasia in the femur and skull, cyst-like lesions in the proximal humerus and non-osteochondral fibromas exclusively in the lower limbs. What could improve the quality of treatment for children with primary proliferative bone diseases is the establishment of centres of paediatric orthopaedic oncology skilled in early diagnosis and prompt management.

Minor Shoulder Injury Reveals Spontaneous Regression of Proximal Humerus Osteochondroma

Osteochondromas are the most common benign bone tumor; nonetheless, the natural history is poorly understood as a result of the low threshold for resection and the fact that many of these lesions are asymptomatic and therefore never diagnosed. We present a case of a 17-year-old patient whose routine shoulder X-ray evaluation, due to a minor shoulder injury, revealed spontaneous regression of a previously documented left proximal humerus osteochondroma at six years follow-up. The likelihood of spontaneous regression should be better understood by orthopedic surgeons and taken into account in the decision process of whether to remove osteochondromas surgically or wait.

Chondrosarcomas in children and adolescents

Chondrosarcomas in children and adolescents are uncommon and constitute < 5% of all chondrosarcomas. There are very few studies discussing extremity chondrosarcomas in young patients.

The pelvis is the most common site, followed by the proximal femur.

As cartilaginous tumours can be quite challenging to diagnose, it is best for these lesions to be discussed in a multidisciplinary meeting which includes a radiologist and a pathologist specializing in bone tumours.

Treatment principles are similar to those in adults, with adequate surgical excision respecting oncologic principles being the mainstay of treatment. Select extremity Grade I chondrosarcomas may be managed with extended intralesional curettage without increasing the risk for local recurrence or metastatic disease, but case selection is critical and should be based on clinical, imaging and histological characteristics.

Chondrosarcomas are resistant to chemotherapy and relatively radioresistant. For mesenchymal chondrosarcomas, there may be a role for chemotherapy, though data on this is limited.

Prognosis and rate of recurrence correlate directly to the adequacy of the surgical resection.

Chondrosarcomas in younger patients behave in a similar fashion to those in adults, and outcomes in the young are no different from those in adults.

Cite this article: EFORT Open Rev 2020;5:90-95. DOI: 10.1302/2058-5241.5.190052

Characterization of Solitary Lesions in the Extremities on Whole-Body Bone Scan in Patients With Known Cancer: Contribution of Single-Photon Emission Computed Tomography/Computed Tomography

Background: Solitary lesions in the extremities showing ^99mTc-methylene diphosphate (MDP) uptake are often encountered on whole-body bone scan (WBS), and proper interpretation of this diagnostic method is important for patients with known cancer. The purpose of this study was to summarize the characteristics of solitary lesions in the extremities of patients with known cancer and to evaluate the diagnostic accuracy of single-photon emission computed tomography/computed tomography (SPECT/CT) in differentiating bone metastases from benign bone lesions.

Methods: This study was a retrospective review of 86 patients (54 males and 32 females; mean age, 57.88 ± 10.97 years; range, 31–81 years) with known cancer who underwent WBS and showed solitary lesions with ^99mTc-MDP uptake in the extremities and then underwent SPECT/CT for further diagnosis. SPECT/CT images were independently interpreted by two experienced nuclear medicine physicians. The diagnostic accuracy of SPECT/CT in differentiating malignant from benign solitary lesions in the extremities was evaluated. Inter-reviewer agreement was assessed by using weighted k statistics. The standard diagnostic criterion was based on biopsy or radiologic follow-up over at least 12 months.

Results: In total, 23 bone metastases and 63 (73.26%) benign lesions were diagnosed. The majority (16/23, 69.57%) of bone metastases were found in the diaphyses. The most common benign bone disease was a benign bone tumor (31.75%, 20/63). The majority (13/20, 65%) of benign bone tumors were enchondromas. In the proximal and distal extremities, the most common disease was degeneration (27.11%, 16/59), followed by benign bone tumors and osteonecrosis of the femoral head (ONFH) (22.03%, 13/59). In the diaphyses of the extremities, bone metastasis was the most common disease, accounting for 64% (16/25) of the findings. For the SPECT/CT analysis, the accuracy was 94.19% (81/86) for reviewer 1 and 95.34% (82/86) for reviewer 2. The weighted kappa score for inter-reviewer agreement was 0.813.

Conclusion: When solitary disease of the extremities is detected by WBS in patients with known cancer, benign lesions may be more common than malignant lesions. SPECT/CT resulted in not only fewer equivocal lesions but also in higher diagnostic accuracy.

Osteochondroma: Review of 431 patients from one medical institution in South China

BACKGROUND

The geographic distribution of osteochondroma (OC) varies greatly around the world. There has been no recent report on OC in a large Chinese population. The aim of this study was to characterize OC by an epidemiological analysis of the clinical data from one medical institution in South China.

METHODS

We searched medical electronic records from January 2001 to January 2016 in one large hospital in South China to identify patients with a definite diagnosis of OC. Their epidemiological data were collected and analyzed statistically, including gender, tumor site, age at first diagnosis and symptoms, local recurrence and malignant transformation. Differences between genders and between solitary osteochondroma (SO) and multiple osteochondroma (MO) were particularly analyzed.

RESULTS

A total of 431 OC patients (291 males and 140 females; 329 SOs and 102 MOs) were identified. The gender ratio was 2.08 with a male predominance. OCs were mostly located around the knee (250 cases). 280 patients were in their 0s to 20s upon first diagnosis. The average age at the time of first diagnosis was 20.63 years for all, 18.47 years for males and 25.11 years for females (P=0.000). OC recurred locally in 35 patients (15 SOs and 20 MOs), with a significant difference between SO/MO (P=0.000) but not between genders (P=0.100). The average interval from the primary surgery to local or malignant recurrence was 37.41 months. Malignant transformation was found in 5 patients (4 males and 1 female), showing no gender difference (P=0.549).

CONCLUSIONS

OC may have a male predominance in Chinese population. It mostly occurred at 0-20 years of age and around the knee. Upon the first diagnosis of OC, the males tended to be younger than the females, and so did the MO patients than the SO ones. In addition, MO had a higher incidence of local recurrence. Intervals from primary surgery to local recurrence or malignant transformation in MO patients were longer than in SO patients.

Three-dimensional printing and computer navigation assisted hemipelvectomy for en bloc resection of osteochondroma: A case report

RATIONALE

Three-dimensional (3D) printed templates can be designed to match an individual's anatomy, allowing surgeons to refine preoperative planning. In addition, the use of computer navigation (NAV) is gaining popularity to improve surgical accuracy in the resection of pelvic tumors. However, its use in combination with 3D printing to assist complex pelvic tumor resection has not been reported.

PATIENT CONCERNS

A 36-year-old man presented with left-sided pelvic pain and a fast-growing mass. He also complained of a 3-month history of radiating pain and numbness in the lower left extremity.

DIAGNOSES

A biopsy revealed an osteochondroma with malignant potential. This osteochondroma arises from the ilium and involves the sacrum and lower lumbar vertebrae.

INTERVENTIONS

Here, we describe a novel combined application of 3D printing and intraoperative NAV systems to guide hemipelvectomy for en-bloc resection of the osteochondroma. The 3D printed template is analyzed during surgical planning and guides the initial intraoperative bone work to improve surgical accuracy and efficiency, while a computer NAV system provides real-time imaging during the tumor removal to achieve adequate resection margins and minimize the likelihood of injury to adjacent critical structures.

OUTCOMES

The tumor mass and the invaded spinal structures were removed en bloc.

LESSONS

The combined application of 3D printing and computer NAV may be useful for tumor targeting and safe osteotomies in pelvic tumor surgery.

Retrofibular osteochondroma with peroneal tendon subluxation

Osteochondroma of the bone can cause a range of complications involving tendons, joints and neurovascular structures. Distal fibular osteochondroma and non-traumatic peroneal tendon subluxation are both rare. In this case report, we describe an unusual case of distal retrofibular osteochondroma in a 36-year old male causing peroneal tendon subluxation. He presented with pain and instability around his ankle, but with no history of trauma. He successfully underwent osteochondroma excision, peroneal groove deepening and a Brostrom-Gould type reconstruction for the lateral ankle ligament insufficiency. Complete resolution of the symptoms of instability and subluxation was noted upon 6-month follow up.