Osteochondroma - Erler Zimmer

Osteochondroma - Erler Zimmer

Clinical History

A 61-year-old male diagnosed with prostate cancer undergoes pre-assessment before a prostatectomy. Despite overall well-being, he reports chronic pain in his right knee, previously diagnosed by his GP as osteoarthritis. To rule out bony metastases of the prostate carcinoma, a knee x-ray is conducted, revealing a pedunculated lesion projecting from the medial aspect of the diaphysis of the right femur. The patient proceeds with the prostatectomy but unfortunately succumbs to a postoperative pulmonary embolism.

Pathology

The specimen consists of the lower end of the patient's right femur, cut in the coronal plane and mounted to display external surfaces. A 2 cm pedunculated bony protuberance projects from the medial aspect of the femoral shaft, 7 cm above the medial condyle. The projection comprises normal bone with a thin cap of hyaline cartilage at the tip, indicative of an osteochondroma.

Further Information

Osteochondromas, also known as exostoses, are benign cartilaginous tumors characterized by a cartilaginous-capped bony protrusion from the bone's external surface. They rank as the most common benign bone tumors, typically developing spontaneously but also associated with multiple hereditary exostosis syndrome or post-radiotherapy. Originating near the growth plate, they commonly arise in the appendicular skeleton, especially around the knee or proximal humerus. Men are more frequently affected than women.

Symptoms vary based on the growth's site and size, with many osteochondromas remaining asymptomatic. Compression of surrounding neurovascular structures can lead to symptoms, along with potential pain from myositis or bony spur fractures. Diagnosis is often made through plain x-rays, although MRI serves as the gold standard to rule out malignancy within the growth.
Hereditary exostoses are linked to mutations in the EXT1 and EXT2 genes, with reduced expression also observed in sporadic cases. Osteochondromas cease formation with growth plate fusion. Surgical excision is considered only for severe symptoms, and malignant transformation to chondrosarcoma is rare in sporadic cases but more common in hereditary exostosis (5-20%).