Small soft tissue sarcomas do metastasize: identification of high-risk tumors

Small (≤ 5 cm) soft tissue sarcomas (STS) of the extremities and the trunk wall generally have a favorable prognosis. However, 1 of 10 patients do develop metastases, and we therefore aimed to determine predictors of metastasis in a population-based cohort of patients with small STSs.

In the southern Sweden health care region, 848 adult patients with STS of the extremities or the trunk wall were diagnosed between 1986 and 2010. Of these, 243 STS (29 %) were ≤5 cm. Prognostic evaluation was performed in 229 patients with localized disease at diagnosis, 181 of whom had histologic high-grade tumors.

None of the 48 patients with low-grade tumors developed metastases, whereas 24 of 181 patients with high-grade tumors (13 %) tumors did. Presence of either tumor necrosis or vascular invasion predicted development of metastases with a hazard ratio of 2.9 (95 % CI, 1.0-7.9), and tumors with both factors had a hazard ratio of 12 (95 % CI, 4.1-37) for metastasis (adjusted for size).

Our population-based series of STSs ≤5 cm demonstrate an overall good prognosis with metastases developing in 13 % of the patients with high-grade tumors. Tumor necrosis and vascular invasion were the major predictors of metastatic disease in this subset. Tumors with both these risk factors metastasized in 8 of 18 patients, which corresponds to a 12-fold increased risk of metastasis. These findings suggest that although small STS generally are linked to a good prognosis, necrosis and vascular invasion are features indicating biologically aggressive tumors for which treatment and surveillance should equal that for larger tumors.