Myoid differentiation and prognosis in adult pleomorphic sarcomas of the extremity

Abstract

BACKGROUND The results of a recent study demonstrated an association between myoid differentiation and an adverse prognosis in adult patients with pleomorphic sarcoma, as determined by 5‐year metastasis‐free survival rates. METHODS To confirm the importance of muscle differentiation on prognosis in a well controlled clinical context, 92 samples from patients with pleomorphic sarcoma of the extremity from a single institution were immunostained with 4 monoclonal antibodies believed to be correlated with myoid differentiation: α‐smooth muscle actin, muscle‐specific actin, desmin, and myoglobin. RESULTS Forty‐two cases were positive for at least 1 muscle marker and 50 cases were uniformly negative. Between the two groups, there was no significant difference in tumor size, tumor extent, or patient age found; however, histologic grade was significantly higher (P = 0.038) in the myoid tumors. The 5‐year survival differed significantly between patients with myoid tumors (35%) and those without myoid tumors (65%) (P = 0.0054). Myoid differentiation remained an adverse prognostic indicator after adjusting for clinically significant factors (i.e., histologic grade, tumor size, tumor extent, and patient age) (P = 0.01) (hazard ratio, 2.39; 95% confidence interval, 1.24–4.63). Furthermore, there was an inverse relation found between the number of myoid markers present and survival (P = 0.004). CONCLUSIONS Myoid differentiation was found to be an independent indicator of adverse prognosis in adult patients with pleomorphic spindle cell sarcoma of the extremity. Cancer 2003;98:805–13. © 2003 American Cancer Society. DOI 10.1002/cncr.11617