| disease | Chondromyxoid Fibroma |
Chondromyxoid fibroma of bone is a rare benign tumor. It originates from connective tissue that forms cartilage and is easily confused with osteosarcoma or chondromyxoid fleshy tumor. Although histomorphologically, the tumor contains both cartilaginous tissue and myxoid material with large nuclei or bizarre-shaped cells among small round cells, resembling malignancy, the tumor progresses slowly and follows a benign course. Clinically, symptoms are mild, and complete surgical removal generally prevents recurrence, with metastasis being extremely rare.
bubble_chart Pathological Changes
(1) Gross Findings The tumor often occurs in the metaphysis of large bones and generally does not invade the epiphysis. When the tumor occurs in short bones, it may eventually involve the entire diaphysis. The tumor has clear contours and is usually small, with a diameter ranging from 2 to 8 cm. In the cartilaginous areas, the tumor tissue appears white, slightly glossy, and firm, lacking the bluish-white color and lobulated structure typical of normal cartilage tissue. In the mucoid areas, the lesion appears grayish-white, soft, and brittle, without the slippery, viscous sensation characteristic of typical mucoid tissue.
(2) Microscopic Examination The tumor exhibits a lobulated structure, composed of cartilaginous, myxoid, and fibrous components. The main feature is spindle-shaped or stellate cells loosely distributed in a myxoid intercellular matrix. The central part of the tumor contains smaller cells, while the periphery is more densely packed, forming a pseudolobulated pattern. The tumor stroma may undergo collagenization, and the more mature the tumor, the more collagen fibers are present.
The disease commonly occurs in adolescents, with no gender difference. 80% of cases are seen in individuals under 30 years old, while it is rare in children under 10. It predominantly affects the lower limbs, particularly the upper tibia, femur, and lower fibula, though some cases occur in the metatarsals, calcaneus, ribs, and hip bones, with rare instances involving the spine. Lesions are mostly located near the metaphysis. In long bones, the tumor often grows eccentrically and may invade and destroy the local cortical bone. In short tubular bones, the tumor completely occupies the medullary cavity and causes local expansion.
Clinical symptoms are mild, primarily presenting as localized pain and swelling. Some patients may initially have no discomfort, and the tumor is only discovered through imaging after trauma.
X-ray findings: In long bones, the typical presentation is a round or oval radiolucent area located eccentrically at the bone end, sometimes lobulated or honeycombed. The peripheral contour is irregular, showing a wavy appearance or triangular bone ridges protruding toward the center, with clear demarcation from normal bone. The affected bone may exhibit grade I or grade II expansion, and adjacent bone tissue often shows sclerosis, with possible speckled calcifications in the tissue. The local cortex is thinned, and most cases show no periosteal reaction, nor any mass shadow in the nearby soft tissues. In small tubular bones, chondromyxoid fibromas are often centrally located in the medullary cavity and may involve most or all of the bone.
bubble_chart Treatment Measures
The effective treatment for this disease is complete tumor resection combined with bone grafting or surgical curettage, with a possibility of recurrence. It is generally believed that the younger the patient, the higher the likelihood of recurrence. The local recurrence rate after curettage is approximately 25%, and recurrent tumors are prone to malignant transformation. Although this tumor is a benign lesion with grade I invasiveness, distant metastasis is rare. Amputation is only considered when malignant transformation is confirmed.
(1) Giant cell tumor Mostly seen in the epiphyseal region, with significant local cortical expansion and thinning. Primarily manifests as osteolytic destruction, often with multiple interwoven linear bony septa, sometimes presenting a typical soap-bubble appearance, and prone to pathological fracture.
(2) Bone cyst More commonly found in the upper end of the humerus and femur. The tumor is located in the central metaphysis and expands outward, with a relatively uniform radiolucent area. The bony septa in multilocular bone cysts are also relatively fine.
