Myxoid Liposarcoma?Frequency and the Natural History of Nonpulmonary Soft Tissue Metastases

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Abstract
Background: Myxoid liposarcomas (ML) make up the major subset of liposarcomas, which in most series represent the second or third most common type of soft tissue sarcoma. The tendency for ML to metastasize to other soft tissues (STM) in preference to lung parenchyma has been previously described; however, the natural history of this tumor’s behavior is poorly documented. Our intent was to analyze the natural history of ML and further quantify the incidence of STM, concentrating on their significance in terms of survival. Methods: We reviewed the experience at the Royal Marsden Hospital over a 10-year period, documenting the clinicopathological behavior of ML, including the frequency of STM. Results: There were 50 patients, with a median follow-up of 43 months. The actuarial 5-year soft tissue metastasis rate was 31%, and the most common sites of STM were the retroperitoneum, abdominal wall, and abdominal cavity. In those 12 patients who had STM there was a median interval of 23 months after original diagnosis to the time the first metastasis became apparent (range, 0–142 months). Median survival following first metastasis was 35 months; 6 of the 12 patients died between 6 and 50 months. Four patients who had STM remain disease free at 15 to 59 months after their first STM. Any round cell component of the ML was associated with a significantly greater chance of metastatic disease (P = .02). In this series, the overall 5-year and 7-year survival rates were 85% and 68%. Patients with STM had an 11 times greater chance of dying than those who did not. Conclusions: ML usually is an indolent disease, but there is a subset of patients who develop STM and have a significantly worse prognosis. STM can occur years after the initial diagnosis and can be associated with medium-long-term survival after they occur. STM should be managed aggressively because of this.