Metastasizing chondroblastoma: a rare bone tumor no longer supported by the WHO classification

Comprehensive Insights into Chondroblastoma Metastasis: Metastatic Patterns and Therapeutic Approaches

Chondroblastoma metastasis, though rare, represents a clinically significant and notably important aspect of bone tumors. Understanding its epidemiological characteristics, pathological features, and treatment modalities, despite its infrequency, is imperative for comprehensive patient management. This review aims to elucidate the epidemiology, molecular mechanisms, diagnostic challenges, and therapeutic strategies associated with chondroblastoma metastasis. The patterns, prognostic factors, and treatment outcomes were explored through an analysis of case studies and clinical reports. Notably, we highlighted emerging therapeutic perspectives aimed at improving patient outcomes. To the best of our knowledge, there has been no previous review addressing these matters cumulatively, highlighting a significant gap in the existing scholarly literature. By shedding light on the nuances of chondroblastoma metastasis, this review contributes to the advancement of knowledge in this field and informs clinical decision-making for improved patient care.

Bone metastases from chondroblastoma: a rare pattern of metastatic disease in an adult

Chondroblastoma is a rare benign tumor, typically presenting in the first two decades. Systemic metastases in chondroblastoma are extremely rare and it is the rarity of these metastases which lead the World Health Organisation to re-classify this lesion from "intermediate" to "benign" in its updated classification of bone tumors in 2020. We present an unusual case of a 55 year-old male patient who presented with multiple FDG-avid bone lesions on a background of conventional chondroblastoma of the rib excised at another institution 11-years previously. Two of these lesions were also histologically-proven as conventional chondroblastoma at biopsy. This case highlights that, although rare, metastases can be seen in patients with chondroblastoma. To our knowledge, this is the only case with an unusual pattern of metastases limited to bone.

Malignant Transformation in a Chondroblastoma-Does it Exist?

Chondroblastoma is currently described as a benign bone tumor, histopathologically characterized by its classical features including chondroblasts, pink cartilage, and a variable number of osteoclast-like giant cells with foci of dystrophic calcification. Although recurrent and metastasizing chondroblastomas are reported, a malignant chondroblastoma is exceedingly rare and somewhat a contentious entity. A 35-year-old male presented with a lump in his ankle of 15 years' duration. Imaging disclosed a lytic destructive lesion involving the lower ends of the tibia and fibula with a soft tissue component, indicative of atypical/"worrisome" features. Microscopic examination of the biopsy revealed distinct foci of chondroblastoma, transitioning to areas of high-grade sarcoma, including pleomorphic cells, increased mitoses, and prominent stromal hyalinization. Immunohistochemically, the entire tumor was positive for H3K36M, while DOG1 highlighted the areas of chondroblastoma. SATB2 highlighted the areas of high-grade sarcoma, sparing the areas of chondroblastoma. Additionally, the areas of a high-grade sarcoma showed multifocal desmin immunostaining. A diagnosis of a malignant transformation in a chondroblastoma was offered. The patient defaulted to further treatment and unfortunately died 8 months, post-diagnosis. The conceptual evolution of a malignant chondroblastoma with H3K36M immunostaining in the few reported tumors is described herewith.

Chondroblastomas in Children and Young Adults: Revision of 55 Cases

BACKGROUND

Chondroblastomas are uncommon primary bone tumors localized in long bone epiphyses in children and young adults. The risk of metastasis is rare, but they have a high capacity for local recurrence. Surgical curettage with bone grafting or bone substitute is the preferred treatment.

METHODS

We performed an observational retrospective study of chondroblastomas treated in 2 hospitals in Barcelona from 1988 to 2018. We reviewed the location of the tumor, clinical presentation, imaging, histopathology, initial treatment, and cases of recurrence with a review of their treatment. We assessed the correlation between recurrence and index surgery, anatomic location, and certain histopathologic findings (presence of mitotic figures, necrosis, and positivity for protein S-100).

RESULTS

The series included 55 patients treated from 1988 to 2018, with ages ranging from 6 to 26, and a mean follow-up of 6.1 years (±3.7). The most common location was the distal femur metaphyseal/epiphyseal region. The most frequent clinical presentation was pain in the affected. Forty-five cases (81.8%) were treated with curettage of the tumor, and 4 cases (7.3%) with a wide resection. Forty-two cases (85.7%) received bone substitutes after curettage or resection. We found 5 cases of recurrence (9.1% recurrence rate); however, we could not find a statistically significant correlation between index surgery and recurrence ( P =0.24), anatomic location and recurrence ( P =0.49), or recurrence and histopathologic findings (mitotic figures, P =0.49; necrosis, P =0.60; positivity for protein S-100, P =0.52). In all the cases the treatment for the local recurrence was surgical, with a final healing rate of 100%.

CONCLUSIONS

Chondroblastomas should be considered in children and adolescents when presenting with pain and an image suggestive of a tumoral lesion on plain x-ray, most frequently in epiphyses of long bones.Surgical treatment is preferred, obtaining good results after curettage and bone substitute. Chondroblastomas are tumors with a high capacity for recurrence, therefore an adequate surgical technique and surgeon experience are paramount to achieve good outcomes.

LEVEL OF EVIDENCE

Level IV (case series). Therapeutic studies-investigating results or treatment.

Recent advances in molecular profiling of bone and soft tissue tumors

The molecular characterization of soft tissue and bone tumors is a rapidly evolving field that has changed the perspective of how these tumors are diagnosed today. Morphology and clinico-radiological context still represent the cornerstone of diagnostic considerations but are increasingly complemented by molecular data that aid in objectifying and confirming the classification. The spectrum of analyses comprises mutation or gene fusion specific immunohistochemical antibodies, fluorescence in situ hybridization, DNA and RNA sequencing as well as CpG methylation profiling. This article provides an overview of which tools are presently available to characterize bone and soft tissue neoplasms molecularly, what limitations should be considered, and what conclusions can be drawn from the individual findings.

Pulmonary Metastases of Chondroblastoma in a Pediatric Patient: A Case Report and Review of Literature

Chondroblastoma is a locally destructive, cartilaginous bone tumor that accounts for a small percentage of cases of primary bone tumors. Although considered a benign tumor, chondroblastoma can locally recur and can rarely metastasize. Here, we report a rare presentation of a locally recurrent chondroblastoma with pulmonary metastases. A 13-year-old female presented with palpitations, dry cough, difficulty breathing, and chest tightness four years after her original surgical resection of tibial chondroblastoma. On chest CT, multiple pulmonary soft tissue nodules with confluent punctate areas of calcification were seen. The patient underwent robotic-assisted bilateral pulmonary wedge resections. She is now undergoing denosumab therapy. This case underlined the importance of suspecting metastatic disease in patients with a history of chondroblastoma when pulmonary nodules are detected on imaging.

Chondroblastoma of the patella with secondary aneurysmal bone cyst, an easily misdiagnosed bone tumor:a case report with literature review

Background

Chondroblastoma (CB) is a rare, primary, benign bone tumor that commonly affects men aged 15–20 years. It is usually detected in the epiphysis of the long bones, such as the proximal femur, humerus, and tibia. The patella is an infrequent site. CB with secondary aneurysmal bone cyst (ABC) is extremely rare in the patella, which can be easily confused with other common bone tumors of the patella. Thus, it is necessary to make the right diagnosis to get a good outcome.

Case presentation

We have presented here the case of a 30-year-old man who was suffering from anterior knee pain for the past 6 months that had aggravated 2 weeks before the presentation. Osteolytic bone destruction in the patella could be detected in both his X-ray and computed tomography (CT) examinations, while the magnetic resonance imaging (MRI) detected a fluid level. Accordingly, secondary ABC was presumed. We diagnosed the condition as giant cell tumor (GCT) with secondary ABC and, accordingly, performed curettage inside the focus region with autogenous bone grafting following the patient’s medical history, physical manifestations, results of physical and ancillary examinations, and the disease characteristics. However, the intraoperative and postoperative outcomes indicated that the patient’s histopathology was consistent with that of typical CB, suggesting a definitive error in diagnosis. Accordingly, the patient was finally diagnosed with patella CB along with secondary ABC.

Conclusions

Past studies have demonstrated that the 3 commonest bone tumors affecting the patella are GCT, CB, and ABC. CB with secondary ABC can be easily misdiagnosed as GCT with secondary ABC or ABC. Performing incision biopsy or excision biopsy and conducting histological examination may be the most effective method for suspected CB with secondary ABC.