The variety of benign and malignant soft tissue tumors that are seen in children is considerable. They can arise from almost any tissue type and in any part of the body. Some malignant soft tissue tumors respond well to therapy and have a very good prognosis, while some that are technically benign can be locally invasive and extremely difficult to eradicate. They are overall quite rare and because they are easily confused with garden variety benign tumors (lipoma) or dismissed as traumatic lesions, the diagnosis is often a surprise. This also increases the chances that they are treated improperly at first, leading to unnecessary or disfiguring surgery.
Any soft tissue mass in a child should be considered potentially malignant until proven otherwise. In practical terms, this means that one should adhere to certain surgical principles so as to avoid spillage of the tumor and the eventual need to remove more tissue than would otherwise have been necessary. Tumors that are small and easily excised with a margin of normal tissue without creating large soft tissue defects or causing injury to neurovascular structures or normal organs may be excised up front. Larger tumors should be biopsied first. The incision and the tissue planes traversed should be planned carefully so that if a subsequent wide excision becomes necessary, one can incorporate the scar. For extremity lesions, this usually means a longitudinal incision. If the biopsy confirms the presence of a benign lesion, surgical extirpation is usually the only treatment modality available. Some can be simply enucleated while others require an aggressive attempt to remove all gross tumor. Desmoid and IMT are known to sometimes respond to anti-inflammatory drugs or COX-2 inhibitors but surgical resection is still considered the standard approach. For most malignant tumors, neoadjuvant chemotherapy can be used to shrink the tumor and render it resectable or at least minimize the amount of surrounding normal tissue that needs to be excised to achieve tumor-free margins. For most soft tissue sarcomas, the prognosis is the same whether the tumor is resected up front or after chemotherapy, as long as the entire mass is ultimately excised with a margin.
When a tumor needs to be re-excised after a biopsy or ill-advised attempt at resection, the resection plane must stay clear of all previous surgical planes. This entails making an elliptical incision around the previous scar and then staying outside of the postoperative seroma by at least 1–2 cm. Preoperative planning with high-resolution three-dimensional imaging is critical to achieving this goal. If the previous operative site is entered, the risk of subsequent recurrence is much higher. It is especially problematic when the previous operation was associated with significant bleeding or a hematoma, in which case previously uninvolved compartments must now be considered contaminated.
Though likely someday to be supplanted by PET scanning, sentinel lymph node biopsy is being used at some centers to assess the likelihood of metastasis and to guide therapy, especially for some of the more aggressive sarcomas (rhabdomyosarcoma, synovial cell sarcoma). The approach is similar to that used for melanoma, although the customary injection of radiotracer and lymphazurin dye under the skin raises concerns about whether lymphatic drainage from the deeper tissues will be the same. Formal lymph node dissection is rarely indicated. Resection of metastases is also rarely indicated except for the unusual situation in which there are a small number of isolated lung nodules.
Because of the many variations in approach to soft tissue tumors, it is best to consult with a pediatric oncologist before any planned operative procedure. One should always be thinking about the next step in order to avoid making an avoidable error. There are also nationally recognized experts in the COG who can answer questions and give advice regarding the optimal approach to the surgical management of these complex disorders.