Chondromyxoid Fibroma: An Updated Review

Chondromyxoid fibroma (CMF) is a rare benign cartilaginous neoplasm that most frequently occurs in the metaphysis of long bones in adolescents and young adults. The most common symptom is pain and/or swelling in the affected area. Radiographs typically show a well-defined, eccentric lytic lesion with sclerotic margins and scalloped or lobulated borders. Unlike other cartilaginous neoplasms, matrix calcification is uncommon. On magnetic resonance imaging (MRI), CMF usually exhibits low to intermediate signal intensity on T1-weighted sequences and heterogenous high signal intensity on T2-weighted sequences. Contrast-enhanced MRI demonstrates intense homogeneous, heterogeneous or peripheral enhancement. Histologically, CMF is composed of lobules of stellate to spindle-shaped cells in a myxoid background. The periphery of the lobules is generally hypercellular, imparting a characteristic zonal architecture. Recent molecular studies have identified alteration of glutamate metabotropic receptor 1 (<i>GRM1</i>) gene, and GRM1 positivity by immunohistochemistry has emerged as a reliable surrogate marker for this molecular event. Curettage or <i>en bloc</i> resection is the treatment of choice, with a non-negligible risk for local recurrence. This review provides an updated overview of the clinical, radiological, histological, immunohistochemical and molecular genetic features of CMF and discusses the differential diagnosis of this unusual neoplasm.