Malignant soft tissue tumors account for about 7% of malignant tumors in children. About half are rhabdomyosarcomas. These soft tissue malignancies are divided into five general categories. Features that suggest a soft tissue lesion to be malignant include being firm, deep, nontender, and greater than 5 cm in diameter.
This is a sarcoma of the skeletal muscle. Extremity tumors account for 20% and carry a poorer prognosis.
Lesions are firm, nontender, and within the muscle compartment. Tumors occur in childhood, and metastasize to lymph nodes and later to bone. Manage by total excision and chemotherapy. Expect the 5-year survival to be in the 65–75% range.
Malignant Fibrous Tumors
Desmoid tumors or fibromatosis are sometimes considered to be benign. However, because of their high rate of recurrence, they are sometimes considered as low-grade fibrosarcomas. Most occur in the extremities, creating a soft tissue mass and sometimes erosion or deformity of the adjacent bone. The natural history of fibromatoses is variable; lesions often recur and undergo spontaneous remission. Fibromatoses seldom metastasize or cause death.
Manage by total resection when possible. If surgical margins cannot be achieved without sacrificing the limb or its function, excisional resection is an acceptable alternative. The role of chemotherapy is controversial. Radiation therapy is effective but often complicated by growth arrest when the radiation field includes centers of bone growth.
These tumors occur most commonly in adolescents and adults. Most occur in the lower extremities. Primary metastases are usually to regional lymph nodes. Manage by chemotherapy, nonmultilating resection, and radiation. Expect 70–80% survival.
Round Blue Cell Tumors
These tumors include primitive neuroectodermal tumors, soft tissue Ewing sarcomas, and Askin tumors. Askin tumors are round-cell tumors involving the central axis and chest wall.
Peripheral nerve sheath sarcomas Malignant degeneration occurs in 5–10% of patients with neurofibromatosis (NF1). Enlarging lesions in these patients should be documented by MRI and excised or biopsied.
Other sarcomas These include a variety of tumors: leiomyosarcoma, liposarcoma, angiosarcoma, and many others.