Analysis of stromal cells in osteofibrous dysplasia and adamantinoma of long bones

Unraveling molecular signatures in rare bone tumors and navigating the cancer pathway landscapes for targeted therapeutics

Rare cancers (RCs), which account for over 20% of cancer cases, face significant research and treatment challenges due to their limited prevalence. This results in suboptimal outcomes compared to more common malignancies. Rare bone tumors (RBTs) constitute 5-10% of rare cancer cases and pose unique diagnostic complexities. The therapeutic potential of anti-cancer drugs for RBTs remains largely unexplored. Identifying molecular alterations in cancer-related genes and their associated pathways is essential for precision medicine in RBTs. Small molecule inhibitors and monoclonal antibodies targeting specific RBT-associated proteins show promise. Ongoing clinical trials aim to define RBT biomarkers, subtypes, and optimal treatment contexts, including combination therapies and immunotherapeutic agents. This review addresses the challenges in diagnosing, treating, and studying RBTs, shedding light on the current state of RBT biomarkers, potential therapeutic targets, and promising inhibitors. Rare cancers demand attention and innovative solutions to improve clinical outcomes.

Recurrent Adamantinoma With Fibrous Dysplasia-like Feature

Adamantinoma (AD) is a rare, slow-growing primary malignant bone tumor characterized by a biphasic morphology of clusters of epithelial cells and spindle cell osteofibrous components. A strong relationship between AD and osteofibrous dysplasia (OFD) has been proposed, while fibrous dysplasia (FD) has been rarely associated with AD. We present an AD case that was followed and histologically evaluated 3 times over 6 years with different morphological patterns. The tumor in the primary biopsy and after complete resection showed classical features of AD and osteofibrous-like pattern, while the recurrent lesion presented with exclusively spindle cell morphology and was thus diagnosed as FD. However, the extensive immunohistochemical analysis in all 3 lesions revealed strong reactivity for pancytokeratin, vimentin, p63, and podoplanin, which are characteristic for AD. Although, in the FD-like section of the tumor from the first recurrence the positivity of podoplanin was stronger than pancitokeratin, which was variably positive on spindle cells. The present case highlights the problem of diagnosing AD based on a single biopsy with one tumor's component predominating over the other, and at the same time emphasizes the importance of using immunohistochemical staining for keratin and podoplanin when the histopathological features of (osteo)fibrous lesion can be linked to AD.

Adamantinoma: A review of the current literature

Adamantinoma is a rare primary low-grade malignant tumour of the appendicular skeleton most commonly found in the tibia. It has an indolent course, with local recurrences and lung metastases occurring over a protracted duration. There have been several suggestions pertaining to a vascular origin in the literature, however, histogenesis remains unclear. Currently, guidelines are not available pertaining to clinical management. This paper presents an overview of the current literature regarding this unusual malignancy. It also explores disease etiology and acknowledges the benefits and challenges of investigations pertaining to diagnosis. It recognizes a paucity of recommendations regarding appropriate surveillance and follow up. This review aims to assist clinicians in the building of a consensus opinion for optimal adamantinoma case management under current circumstances where formal guidelines do not exist.

Osteofibrous dysplasia of the tibia : the importance of deformity in surveillance

AIMS

Osteofibrous dysplasia (OFD) is a rare benign lesion predominantly affecting the tibia in children. Its potential link to adamantinoma has influenced management. This international case series reviews the presentation of OFD and management approaches to improve our understanding of OFD.

METHODS

A retrospective review at three paediatric tertiary centres identified 101 cases of tibial OFD in 99 patients. The clinical records, radiological images, and histology were analyzed.

RESULTS

Mean age at presentation was 13.5 years (SD 12.4), and mean follow-up was 5.65 years (SD 5.51). At latest review, 62 lesions (61.4%) were in skeletally mature patients. The most common site of the tibial lesion was the anterior (76 lesions, 75.2%) cortex (63 lesions, 62.4%) of the middle third (52 lesions, 51.5%). Pain, swelling, and fracture were common presentations. Overall, 41 lesions (40.6%) presented with radiological deformity (> 10°): apex anterior in 97.6%. A total of 41 lesions (40.6%) were treated conservatively. Anterior bowing < 10° at presentation was found to be related to successful conservative management of OFD (p = 0.013, multivariable logistic regression). Intralesional excision was performed in 43 lesions (42.6%) and a wide excision of the lesion in 19 (18.8%). A high complication rate and surgical burden was found in those that underwent a wide excision regardless of technique employed. There was progression/recurrence in nine lesions (8.9%) but statistical analysis found no predictive factors. No OFD lesion transformed to adamantinoma.

CONCLUSION

This study confirms OFD to be a benign bone condition with low rates of local progression and without malignant transformation. It is important to distinguish OFD from adamantinoma by a histological diagnosis. Focus should be on angular deformity, monitored with full-length tibial radiographs. Surgery is indicated in symptomatic patients and predicted by the severity of the initial angular deformity. Surgery should focus more on the deformity rather than the lesion. Cite this article: Bone Joint J 2022;104-B(2):302-308.

Osteofibrous dysplasia and adamantinoma: A summary of diagnostic challenges and surgical techniques

Osteofibrous dysplasia is an indolent benign fibro-osseous tumor, while adamantinoma is a locally aggressive biphasic malignancy with epithelial and fibro-osseous components. Predominantly arising in the tibial diaphysis of children and young adults, both tumors are resistant to chemotherapy and radiation. Wide surgical resection is regarded as the mainstay of therapy for adamantinoma, and limb-salvage reconstructive procedures can achieve good functional outcomes, albeit with non-negligible rates of complications. This review discusses emerging advances in the pathogenesis, histogenesis, and diagnosis of these entities and presents advantages and limitations of the most common surgical techniques used for their management.

Adamantinomatous tumors: Long-term follow-up study of 20 patients treated at a single institution

BACKGROUND AND OBJECTIVES

Adamantinomas are primary, low-grade malignant tumors of the bone that have metastatic potential to the lungs, lymph nodes, and other regions. The rarity of this disease and its nonspecific symptoms complicate diagnosis.

MATERIALS AND METHODS

Records for 20 patients who underwent treatment for adamantinoma from 1975 to 2018 were reviewed for demographic, clinical, and pathological data, treatment details, postoperative complications, and outcomes.

RESULTS

Patients presented at a median age of 22 years (1-79 years): 14 patients had a localized primary tumor, three presented with local recurrence, and three with metastatic disease. Median tumor size was 5.7 cm (0.5-15.5 cm). Wide excision was performed primarily in 15 cases; the remaining five patients underwent intralesional curettage. At a median follow-up of 7.3 years, 14 patients had no evidence of disease; two patients were alive with disease, and four patients died from the disease. Local recurrence and distant metastasis occurred at a median of 11.4 years (6 month-19 years) and 15.8 years (4 month-23 years) after diagnosis.

CONCLUSIONS

Adequate histopathological diagnosis is crucial to avoid misdiagnosis of this rare tumor. Local and distant recuAbs_Para_meprrence can occur more than 20 years after the initial diagnosis. Life-long follow-up with clinical examination and imaging is required.

Genetic and molecular reappraisal of spindle cell adamantinoma of bone reveals a small subset of misclassified intraosseous synovial sarcoma

Adamantinoma represents a distinct group of bone tumors showing both mesenchymal and epithelial differentiation most commonly involving the tibial diaphysis. Most adamantinomas contain a fibro-osseous component and an epithelial component consisting of squamous or basaloid cells. Adamantinomas are considered malignant neoplasms requiring en bloc excision that frequently recur locally and can rarely metastasize. Rare adamantinomas show an epithelial component consisting predominantly of monomorphic spindle cells, which, combined with an epithelial immunophenotype, can mimic monophasic synovial sarcoma. Synovial sarcoma is very rare in bone. It is considered a high-grade sarcoma that typically necessitates chemotherapy. However, the relationship between spindle cell adamantinoma and intraosseous synovial sarcoma has not been investigated. The current study was prompted by identification of a presumed spindle cell adamantinoma of the tibia with diffuse keratin expression that harbored a SS18 gene region rearrangement. FISH of eight additional bone tumors initially classified as spindle cell adamantinoma based on clinicoradiopathologic findings revealed one additional case with SS18 rearrangement. Histologically, both intraosseous synovial sarcoma and spindle cell adamantinoma demonstrated uniform fusiform nuclei with scant cytoplasm, short fascicles and low mitotic activity. The adamantinomas, but not the synovial sarcomas, were more likely to show overt epithelial differentiation in the form of pseudoglands or squamous nests. Immunohistochemistry of all cases, irrespective of SS18 status, showed diffuse keratin positivity in the spindle cell component, and less consistent EMA positivity. Clinical follow-up was available in both intraosseous synovial sarcomas, one of which recurred and the other metastasized. Two of the six spindle cell adamantinomas with follow-up metastasized. The above findings highlight the morphologic and immunophenotypic overlap between spindle cell adamantinoma and intraosseous synovial sarcoma of the tibia. Investigation of SS18 status to exclude synovial sarcoma is suggested prior to rendering a diagnosis of spindle cell adamantinoma.

MicroRNA-106b inhibits osteoclastogenesis and osteolysis by targeting RANKL in giant cell tumor of bone

Giant cell tumor (GCT) of bone consists of three major cell types: giant cells, monocytic cells, and stromal cells. From microarray analysis, we found that miR-106b was down-regulated in GCT clinical samples and further determined by fluorescence in situ hybridization. In addition, the expression of novel potential target of miR-106b, RANKL, was elevated in GCT along with previously determined targets in other tumors such as IL-8, MMP2 and TWIST. In a RANKL 3′UTR luciferase reporter assays, agomiR-106b repressed the luciferase activity and the effect was eliminated when the targeting site in the reporter was mutated, suggesting a direct regulation of miR-106b on RANKL mRNA. Moreover, overexpression of miR-106b in GCTSCs through TALEN-mediated site-specific knockin clearly inhibited osteoclastogenesis and osteolysis. By grafting the GCT onto the chick CAM, we confirmed the inhibitory effect of miR-106b on RANKL expression and giant cell formation. Furthermore, in an OVX mouse model, silencing of miR-106b increased RANKL protein expression and promoted bone resorption, while up-regulation of miR-106b inhibited bone resorption. These results suggest that miR-106b is a novel suppressor of osteolysis by targeting RANKL and some other cytokines, which indicates that miR-106b may be a potential therapeutic target for the treatment of GCT.

Mutations Preventing Regulated Exon Skipping in MET Cause Osteofibrous Dysplasia

The periosteum contributes to bone repair and maintenance of cortical bone mass. In contrast to the understanding of bone development within the epiphyseal growth plate, factors that regulate periosteal osteogenesis have not been studied as intensively. Osteofibrous dysplasia (OFD) is a congenital disorder of osteogenesis and is typically sporadic and characterized by radiolucent lesions affecting the cortical bone immediately under the periosteum of the tibia and fibula. We identified germline mutations in MET, encoding a receptor tyrosine kinase, that segregate with an autosomal-dominant form of OFD in three families and a mutation in a fourth affected subject from a simplex family and with bilateral disease. Mutations identified in all families with dominant inheritance and in the one simplex subject with bilateral disease abolished the splice inclusion of exon 14 in MET transcripts, which resulted in a MET receptor (MET(Δ14)) lacking a cytoplasmic juxtamembrane domain. Splice exclusion of this domain occurs during normal embryonic development, and forced induction of this exon-exclusion event retarded osteoblastic differentiation in vitro and inhibited bone-matrix mineralization. In an additional subject with unilateral OFD, we identified a somatic MET mutation, also affecting exon 14, that substituted a tyrosine residue critical for MET receptor turnover and, as in the case of the MET(Δ14) mutations, had a stabilizing effect on the mature protein. Taken together, these data show that aberrant MET regulation via the juxtamembrane domain subverts core MET receptor functions that regulate osteogenesis within cortical diaphyseal bone.

Focal fibrocartilaginous dysplasia in the thoracic vertebra: A case report

Focal fibrocartilaginous dysplasia (FFCD) is a rare, paraneoplastic disease that often presents in children and teenagers. Previous studies have reported cases of lesions in the proximal tibia and distal femur, as well as lesions in the upper extremities. The present study describes a case of FFCD on the transverse process and the rib. The imaging findings were found to correspond with the typical observations of FFCD and a biopsy from the nidus revealed pathological results similar to those of previous reports. Thus, the present study demonstrated that FFCD affects tubular bones as well as flat bones. Further studies are required to investigate the underlying mechanism and treatment of FFCD.