What type of tumor is characterized by large infiltrative masses consisting of clonal proliferation of myofibroblasts?

The type of tumor characterized by large infiltrative masses consisting of a clonal proliferation of myofibroblasts is the desmoid tumor. Desmoid tumors, also known as aggressive fibromatosis, arise from deep tissue and are known for their locally aggressive behavior, with a high propensity for infiltration into surrounding tissues, making their surgical removal challenging.

The myofibroblasts, which are a key component in these tumors, are responsible for the desmoid's fibrous and infiltrative nature. They can resemble both smooth muscle and fibroblast cells, contributing to the tumor's structure and behavior. The clonal proliferation indicates that the tumor arises from a single lineage of cells, which gives it the characteristics that define desmoid tumors, including their variable growth patterns and potential for recurrence.

Other types of tumors mentioned, such as fibromas and myofibromas, tend to have different growth patterns and characteristics. Fibromas typically are less aggressive and do not present with the same infiltrative qualities as desmoid tumors. Myofibromas, while they also contain myofibroblasts, are generally benign and occur predominantly in children. Liposarcomas, on the other hand, are malignant tumors that arise