Fibrocartilaginous mesenchymoma

Last revised by Joachim Feger on 20 Dec 2022

Fibrocartilaginous mesenchymomas are very rare locally aggressive mesenchymal bone tumors composed of spindle cells seen in children and adolescents.

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The term 'fibrocartilaginous mesenchymoma with low-grade malignancy' has been discouraged 1.

Fibrocartilaginous mesenchymomas are very rare tumors. They occur in children, adolescents and young adults up to the third decade 1-3. The male gender is slightly more frequently affected 1.

The diagnosis of fibrocartilaginous mesenchymoma is based on a combination of typical radiographic and pathological features as well as the age of the patient.

Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5th edition) 1:

  • imaging features of a bone tumor

  • spindle cells with mild atypia

  • areas with growth plate-like hyaline cartilage and trabecular bone

An additional desirable criterium is that the patient is younger than 30 years.

The tumors might present as swelling and/or painful lesions or might be entirely asymptomatic and incidentally found 1.

Fibrocartilaginous mesenchymomas are a tumor made up of mildly atypical spindle cells and growth plate-like cartilaginous nodules with bony trabeculae 1-6.

The etiology of fibrocartilaginous mesenchymoma is unknown 1.

Fibrocartilaginous mesenchymomas have been most commonly found in the following locations 1-6:

Macroscopically fibrocartilaginous mesenchymomas have a tannish-white appearance with interspersed bluish-grey shimmering cartilaginous areas. There might be cortical destruction in resected specimens 1.

Microscopically fibrocartilaginous mesenchymomas are characterized by the following histological features 1:

  • hypocellular to a moderately cellular spindle cell component

    • spindle cells arranged in bundles or fascicles

    • slightly hyperchromatic mildly atypical nuclei

    • rare or absent mitoses

  • benign-appearing cartilaginous nodules with chondrocytes arranged in parallel columns

  • areas of enchondral ossification

  • occasional multinucleated giant cells

  • infiltration of the host bone

Immunohistochemistry stains are not helpful in diagnosis 1.

Fibrocartilaginous mesenchymomas lack mutations in GNAS, IDH1 and IDH2 as well as amplifications of MDM2 1,6.

Fibrocartilaginous mesenchymomas appear as lytic expansile lesions on imaging often in an eccentric location 1-5.

On plain radiographs, fibrocartilaginous mesenchymomas appear as lytic expansile lesions with a hazy internal matrix, ring-like calcifications and features of cortical thinning and/or destruction 1,3.

CT might show an expansile lytic tumor with calcifications, cortical thinning or cortical destruction and extension in the adjacent soft tissues 1.

MRI show an expansile lesion with dense fibrous areas mixed with epiphyseal chondroid components and features, cortical destruction and soft tissue extension. 

Signal characteristics are usually as follows 1:

  • T1: low signal intensity

  • T2: high signal intensity

  • T1 C+ (Gd): strong enhancement

The radiological report should include a description of the following:

  • form and location

  • tumor margins and transition zone

  • endosteal scalloping

  • cortical breakthrough

  • infiltration of the surrounding tissues

Management is surgical and excision with wide margins is considered best. Local recurrences might occur after incomplete excision. Metastases or tumor-related death have not been described 1-3.

The entity was first described by the American pathologist David Carl Dahlin and his American and Italian colleagues Franco Bertoni, John W Beabout and Mario Campanacci in 1984 3-6.

Conditions that can mimic the appearance of a fibrocartilaginous mesenchymoma include 1-5:

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