Malignant mesenchymomas are rare, aggressive soft tissue or bone cancer tumors (sarcomas) that contain two or more subtypes of sarcoma.

Symptoms of malignant mesenchymomas depend on the location of the cancer and may include the presence of a mostly painless, rapidly enlarging nodule in the lower extremities, upper arms, head and neck, heart, retroperitoneum, viscera, distal or proximal femur (upper leg), proximal tibia (lower leg), and humerus (upper arm). Additional symptoms of malignant mesenchymomas may include pain, swelling, malaise, lack of appetite, constipation, fever, and weight loss.

Treatment for malignant mesenchymomas depends on the location of the cancer but may include surgery, radiation therapy, chemotherapy, targeted therapy, and immunotherapy.