Chondromyxoid Fibroma of the Iliac Bone: A Case Report with Ultrastructural Observations

Chondromyxoid fibroma of the iliac bone: a brief radiological review

Chondromyxoid fibroma (CMF) is a rare, benign bone tumour most commonly located within the metaphyseal region of the long bones surrounding the knee joint. Here, we present an interesting case of a young woman in her early 20s with CMF of the left iliac bone and include a literature review of comparable studies with an emphasis on radiological findings and important differential diagnoses to be aware of in this atypical location.

Cell biology and matrix biochemistry of chondromyxoid fibroma

We studied matrix composition and gene expression pattern in chondromyxoid fibromas on the protein and the messenger RNA levels. We could clearly identify focal chondrocytic differentiation within chondromyxoid fibroma by the expression and deposition of type II collagen, which is a marker of chondrocytic cell differentiation. We also were able to show expression of collagen types I, III, and VI in the neoplasm. The major tumor portion was, however, characterized by the presence of hydrated proteoglycans and only minor amounts of collagens, a matrix composition responsible for the myxoid matrix appearance of most parts of these neoplasms. By analyzing cytoprotein expression, we found S-100 protein restricted to cells of the chondroid areas, suggesting S-100 protein staining to be of little help as a positive diagnostic marker for chondromyxoid fibroma. Our data show a specific matrix composition of chondromyxoid fibroma, not previously found in other mesenchymal neoplasms, including chondroblastoma, osteochondroma, enchondroma, and chondrosarcoma. This justifies chondromyxoid fibroma as a specific neoplastic entity, both clinically and biologically.