Osteosarcoma of femur - Erler Zimmer

Osteosarcoma of femur - Erler Zimmer

Clinical History

A 16-year-old male presented with a 3-month history of an increasingly swollen and painful right knee. Upon examination, a palpable tender swelling was noted above the right knee. Blood tests revealed an elevated Alkaline Phosphatase level. A knee x-ray displayed periosteal reactive changes in the distal femur, raising suspicion of a bone malignancy. Subsequently, the patient underwent staging CT and MRI evaluations of the right leg. Adjuvant chemotherapy preceded the resection of his right femur, and he achieved a full recovery.

Pathology

The specimen comprises the patient's excised distal femur, revealing a large pale infiltrating tumor measuring 10 cm in greatest diameter. The tumor extends through the periosteum near the articular surface, confirming the diagnosis of osteosarcoma of the femur.

Further Information

Osteosarcomas are malignant bone tumors characterized by the production of osteoid matrix or immature bone, representing the most common primary bone malignancy. Most often found in the distal femur, with the tibia and humerus being frequent sites, osteosarcomas exhibit a bimodal age distribution. The majority occur in children and adolescents under 20 years old, with a second peak occurring in older adults over 60.

Secondary osteosarcomas are more prevalent in older patients, arising in bones with predisposing conditions such as Paget's disease, bone infarcts, and previous irradiation. Mutations in tumor suppressors and oncogenes, including RB, TP53, and INK4a, have been identified in osteosarcomas.

Osteosarcomas typically present with painful, enlarging masses, and pathological fractures may be the initial complaint. Constitutional symptoms are usually absent. Elevated levels of Alkaline Phosphatase and lactate dehydrogenase may be observed in blood tests. X-rays may reveal features of bone destruction, a mass, or signs of a periosteal reaction, such as a sunburst appearance or triangular shells of reactive bone (Codman's Triangle). MRI evaluates local staging of the tumor, while body CT assesses distant spread. In some cases, the tumor may be biopsied.
The most common sites for distant metastases are the lungs, followed by bones and the brain. Treatment involves neoadjuvant chemotherapy followed by surgery. The 5-year survival rate for localized osteosarcoma is 60-70%, dropping to less than 20% in patients with distant metastases.