61-year-old male noticed a recently painful swelling of the right thigh. (Surgical specimen).
- A section of a skeletal muscle is shown containing in its center a circumscribed tumor.
- The tumor is composed of spindle cells exhibiting polymorphic nuclei with coarse chromatin. Some tumor cells contain grotesquely enlarged nuclei. Many mitoses are observed.
- Tumor shows a distinctly infiltrative growth pattern into the surrounding tissue. In addition, vascular invasion is observed.