What type of bone tumor is associated with patients aged 20 to 40 years?

The correct choice is associated with giant cell tumors, which typically occur in young to middle-aged adults, specifically those between 20 and 40 years old. These tumors are characterized by the presence of multinucleated giant cells and commonly arise around the knee, particularly in the distal femur and proximal tibia.

Giant cell tumors often present as painful swellings and may lead to significant joint dysfunction due to their location and aggressive nature, but they are generally benign. They can, however, metastasize, particularly in cases that are diagnosed late or not treated appropriately.

In contrast, chondroblastomas, while also affecting younger individuals, are primarily seen in patients aged 10 to 25 years. Ewing's sarcoma typically occurs in a slightly younger demographic, usually between the ages of 5 and 25. Osteomas are benign tumors that generally have a much later onset, often appearing in middle to older adulthood and associated more with the craniofacial region. This demographic distinction is important in the clinical setting for differential diagnosis and treatment planning.