RESUMO
<p><b>OBJECTIVE</b>To study the clinicopathological features, immnophenotype and differential diagnosis of low-grade fibromyxoid sarcoma (LGFMS).</p><p><b>METHODS</b>The clinical, radiological and pathological features of 9 cases of LGFMS were reviewed.</p><p><b>RESULTS</b>The patients consisted of six males and three females with ages ranging from 11 to 65 years (mean 31.4 years). Clinically, most cases presented as slowly growing painless masses located in the extremities, trunk and neck. Two cases had a history of a rapid recent enlargement. Three cases presented with recurrent diseases after incomplete resection. Ultrasound showed heterogeneous signal. Precontrast CT and T1-weighted MRI showed a nodular mass of low to isodensity, while contrast-enhanced CT and T2-weighted MRI demonstrated contrasting zonal areas of hypo/hyperintensity. The tumors measured 3 to 16 cm (mean 7.7 cm), with a fibrous to myxoid appearance on cut surface. Histologically, they were composed of alternating collagenous and myxoid areas. A transition between the two areas could be identified. Giant rosette-like structures were observed in 3 cases. The center of the giant rosettes was composed of eosinophilic collagen, which showed centrifugal in arrangement. There was also gradual transition between the giant rosettes and the fibromyxoid component. On high magnification, the tumor was composed of ovoid to spindle-shaped cells with hyperchromatic nuclei. Nuclear atypia was inconspicuous. The tumor cells were arranged mostly in interlacing fascicles or whorls. Vessels were not prominent and necrosis was absent. Immunohistochemically, the tumor cells showed unique staining for vimentin, consistent with a fibroblastic differentiation.</p><p><b>CONCLUSIONS</b>LGFMS is a distinctive low grade fibroblastic sarcoma of young adults. Recognizing the characteristics of the rare entity may help to avoid misdiagnosis. Wide local excision is recommended to avoid local recurrences.</p>