Which of the following is NOT a characteristic of Ewing's sarcoma?

Ewing's sarcoma is a type of malignant bone tumor that most commonly occurs in children and young adults. Its distinctive features include specific imaging characteristics, tumor location, and histological characteristics.

Onion-skin periosteal reaction is a classic radiological sign associated with Ewing's sarcoma, where the periosteum reacts to the tumor's presence by laying down new layers of bone in a concentric fashion, resembling onion skin. This response is a key identifying feature.

The diaphyseal location is also typical for Ewing's sarcoma, which frequently arises in the long bones, particularly in the diaphysis or shaft, distinguishing it from other bone tumors that may affect different parts of the bone.

The presence of a large bony mass is characteristic of Ewing's sarcoma, as the tumor typically has a significant soft tissue component and can lead to noticeable bony lesions visible on imaging studies.

In contrast, pseudopalisading tumor cells are more indicative of glioblastoma multiforme, a type of brain tumor, rather than Ewing's sarcoma. Ewing's sarcoma is characterized histologically by a diffuse pattern of small round blue cells. Therefore, it is not accurate to describe Ewing's sarcoma