<h2>What Is Osteosarcoma?</h2><p><strong>Osteosarcoma</strong> is the most common primary malignant bone tumor, accounting for approximately <strong>800–900 new cases annually</strong> in the United States. It primarily affects <strong>children, adolescents, and young adults</strong> (peak incidence in the second decade of life), with a second smaller peak in patients over 65. The tumor most frequently arises in the <strong>metaphysis of long bones</strong> — particularly the distal femur,...

</style><h2>What Is Malignant Mesothelioma?</h2><p>Malignant mesothelioma is a cancer arising from the mesothelial cells lining the pleura, peritoneum, pericardium, or tunica vaginalis testis. In the United States, its incidence is approximately 0.6–1.0 per 100,000, with about 2,500–3,000 new diagnoses annually, making it one of the more prevalent rare solid tumors. The primary cause is prior asbestos exposure, with a latency period of 20–50 years; most patients are therefore over 60 at the...

</style><h2>What Is Squamous Cell Carcinoma of the Anal Canal?</h2><p>Squamous cell carcinoma of the anal canal (SCAC) is a malignancy arising from the epithelium of the anal canal. In the United States, its incidence is approximately 2.0 per 100,000, with about 10,000 new diagnoses annually — making it one of the more prevalent rare cancers. The primary cause is persistent infection with human papillomavirus (HPV, particularly HPV-16/18); high-risk groups include HIV-positive individuals,...