Evans tumorEvans tumor is an eponym for low-grade fibromyxoid sarcoma, which is considered to be a variant of adult fibrosarcoma. It usually arises in deep soft tissues of the limbs and trunk of young adults as a painless slow growing nodular mass. Macroscopically, the tumor appears tan-white, firm, lobulated, and well-circumscribed, resembling a uterine leiomyoma.
Histologically this low-grade tumor consists of fascicles of spindle cells embedded in a myxoid and focally collagenous stroma. The nuclei are bland and contain small nucleoli. Mitoses are rare and no necrosis is seen. Occasionally, sections of the tumor show large rosettes composed of a hyalinized collagenous core surrounded by tumor cells. This variant of Evans tumor is called hyalinized spindle cell tumor with giant rosettes.
Evans tumor consistently expresses vimentin. It can be focally positive for smooth muscle actin, CD34 and desmin. EMA and S-100 are typically negative.
Evans tumor carries a favorable prognosis. Adequately excised tumors have a 10% recurrence rate and 5 - 10 % metastasis rate.
- H.L. Evans. Low-Grade Fibromyxoid Sarcoma: A Clinicopathologic Study of 33 Cases With Long-Term Follow-Up. Am J Surg Pathol. 2011, 35:1450-1462