Fig. 1

a Coronal CT demonstrates a heterogeneous hypodense intra-abdominal soft tissue mass, with adjacent transverse colon displaced into the pelvis. b Sagittal CT demonstrates the extent of the intra-abdominal mass spanning inferiorly to the pubic symphysis. c H&E stain of ultra-sound guided biopsies shows a hyalinized stroma containing an admixture of mature adipocytes and bland spindle cells with eosinophilic cytoplasm and fascicular arrangement, 10X. d Immunohistochemical stain shows strongly positive smooth muscle actin staining in the spindle cell component supportive of smooth muscle cell differentiation, 10X. e Immunohistochemical stain shows the spindle cell component expressing desmin, supportive of the smooth muscle cell, 10X. f Immunohistochemical staining shows spinal component expressing estrogen receptor, 10X. g Tumor cells are negative for HMB-45 immunoreactivity. The faint staining seen in the image is background mast cells appearing throughout the tumor. h Gross pathology specimen of resected mass with overlying omentum. i Cut section of a tumor with a distinct glistening appearance of the tumor