Fibrocartilaginous mesenchymoma of bone: a single-institution experience with molecular investigations and a review of the literature

Fibrocartilaginous Mesenchymoma of the Spine: A Case Report

CASE

A healthy, 19-year-old woman was incidentally found to have a large, destructive tumor of T11 without neurologic symptoms. Biopsy demonstrated fibrocartilaginous mesenchymoma (FCM). The patient was treated with resection including subtotal corpectomy and T8-L1 fusion with use of cage and allograft strut construct. The patient remained without recurrence over 3 years of follow-up.

CONCLUSION

FCM arising from the spine is a rare tumor, of which this is the sixth report. FCM affects primarily young adults and is benign but locally aggressive, requiring complete excision to prevent recurrence.

Fibrocartilaginous mesenchymoma of pelvis-a potential diagnostic pitfall

Fibrocartilaginous mesenchymoma (FM) is a rare bone tumor mimicking other fibrocartilaginous lesions on imaging and histologically. Hence, it is difficult to diagnose this entity especially on small biopsies. In this article, we report a case of FM mimicking desmoplastic fibroma on biopsy. A 36-year-old male presented with pain in the left hip. Imaging showed a large expansile lytic lesion involving the acetabulum and pubis. The differential diagnosis was suggestive of giant cell tumor, aneurysmal bone cyst, intraosseous desmoplastic fibroma, and chondrosarcoma. Biopsy revealed a low-grade spindle cell lesion with no evidence of osteoid or chondroid matrix. The lack of cartilaginous nodules in the biopsy prompted a preoperative diagnosis of desmoplastic fibroma. The excised mass showed bland spindle cell proliferation, benign cartilage nodules, and epiphyseal plate-like enchondral ossification suggestive of fibrocartilaginous mesenchymoma. Negative immunostaining for SATB2, CDK4, and MDM2 ruled out low-grade central osteosarcoma. Though GNAS mutations were not performed in this case, rimming of the bony trabeculae at the periphery of the epiphyseal growth plate-like cartilaginous nodule ruled out fibrous dysplasia. The absence of cartilaginous component misleads the diagnosis preoperatively in small biopsies.

The 2020 World Health Organization classification of bone tumors: what radiologists should know

Improved understanding of tumor biology through molecular alteration and genetic advances has resulted in a number of major changes in the 2020 World Health Organization's (WHO) classification of bone tumors. These changes include the reclassification of the existing tumors and the introduction of several new entities. A new chapter on undifferentiated small round cell sarcomas of bone and soft tissue was added to classify Ewing sarcoma and the family of Ewing-like sarcomas, which share similar histologies but different molecular and clinical behaviors. Knowledge of the current classification of bone tumors is essential to ensure the appropriate recognition of the inherent biological potential of individual osseous lesions for optimal treatment, follow-up, and overall outcome. This article reviews the major changes to the 2020 WHO's classification of primary bone tumors and the pertinent imaging of selected tumors to highlight these changes.

Fibrocartilaginous dysplasia (fibrous dysplasia and massive cartilaginous differentiation): Case report and literature review

Fibrocartilaginous dysplasia (fibrous dysplasia and massive cartilaginous differentiation or fibrochondroplasia, FCD) is a rare variant of fibrous dysplasia and a term used for cases of fibrous dysplasia with prominent cartilage tissue. A limited number of FCD cases have been reported in the literature, which can be seen in both clinical forms. A 16-year-old male patient, who had been followed for ten years with a diagnosis of polyostotic fibrous dysplasia in the left hip and cranium, presented with pain in the left leg after a fall. A subtrochanteric pathological fracture in the left femur was detected on exam, the lesion area was curetted, and osteotomy and fixation were applied. Microscopic assessment revealed a fibro-osseous lesion of benign spindle cell fibrous connective tissue with woven bone trabeculae, without osteoblastic rim or large areas of benign cartilage nodules. The final diagnosis was fibrocartilaginous dysplasia. In our literature review, 26 cases of FCD were reported so far. Age distribution of patients ranged from 4 to 53 years (mean 15.9) and the male / female ratio was 15/11 = 1.36. Eighteen cases were monostotic, and 8 were polyostotic. In cases with noted clinical and follow-up data, symptom duration ranged from 8 weeks to 18 years (mean 62.2 months), with no recurrence or malignant transformation in a mean follow-up of 21.71 (2-60) months post-treatment. In the cartilage component, there was increased cellularity, some nuclear atypia, binucleation, and myxoid degeneration. This situation simulates benign and malignant entities such as enchondroma, fibrocartilaginous mesenchymoma, well-differentiated intramedullary osteosarcoma, and chondrosarcoma with a differential diagnosis. FCD is a benign and very rare lesion with a prominent chondroid component, but may cause difficulty with differential diagnosis. Awareness of the histopathological and radiological features of FCD cases, their age range, and involvement areas provides an approach to distinguish them from lesions that may be confusing in a differential diagnosis.

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.

Updates from the 2020 World Health Organization Classification of Soft Tissue and Bone Tumours

The fifth edition of the World Health Organization (WHO) classification of soft tissue and bone tumours was published in May 2020. This 'Blue Book', which is also available digitally for the first time, incorporates an array of new information on these tumours, amassed in the 7 years since the previous edition. Major advances in molecular characterisation have driven further refinements in classification and the development of ancillary diagnostic tests, and have improved our understanding of disease pathogenesis. Several new entities are also included. This review summarises the main changes introduced in the 2020 WHO classification for each subcategory of soft tissue and bone tumours.

Fibrocartilaginous mesenchymoma with an unusual location in the rib

Fibrocartilaginous mesenchymoma is a rare bone tumor, with fewer than 35 cases reported in the literature since 1984. This tumor usually occurs in the long bones of children and adolescents. In the current case, the tumor affected a rib. A 17-year-old boy presented with a mass in the right fifth rib. Radiologic findings revealed an osteolytic mass with cortical destruction and calcification; en bloc resection was performed. The tumor showed three distinct histologic features: bland spindle cell proliferation, benign cartilage nodules, and epiphyseal plate-like enchondral ossification. The pathologic diagnosis was fibrocartilaginous mesenchymoma. The patient remains free of disease 1 year after the surgery. Pathological diagnosis of fibrocartilaginous mesenchymoma can be challenging, especially when the tumor occurs in an unusual site. When any fibro-osseous lesion with a cartilaginous component is encountered, the possibility of fibrocartilaginous mesenchymoma should be considered because of its locally aggressive behavior.