PMC7778436_01
Computed tomography: homogenously hypodense pelvic mass (arrow) on axial unenhanced image (A), which appears hypervascular on axial enhanced scan (B).
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CT and MRI examinations. CT scan showed a large, well-defined hypervascular tumor of about 5 x 4 cm located in the cave of Retzius (Figure 1).
Magnetic resonance imaging: the mass shows intermediate signal intensity on axial T1- (A) and T2- (B) weighted images while high-signal intensity on axial T2-weighted-STIR image (C) with areas of signal void preferentially located in the peripheral part (arrow). Post-contrast images on arterial phase in axial plane (D) and delayed phase in coronal view (E) show an intense and persistent enhancement.
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After paramagnetic contrast agent administration, the lesion showed early, strong and persistent enhancement (Figure 2).
Gross features of the lesion specimen are shown (A). Hypercellular areas consisting of bland and uniform oval to spindle cells with minimal cytoplasm, small elongated nuclei and indistinct nucleoli were evident in the hematoxylin and eosin stain, 20 x magnification (B). Strong positivity for STAT-6 was detected, 20 x magnification (C).
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Immunohistochemical analysis revealed that the tumor had a strong positivity for STAT-6 and CD34, low positivity for bcl-2, and negativity for smooth muscle-actin, S-100 protein and desmin, confirming the diagnosis of solitary fibrous tumor (hemangiopericytoma) (Figure 3).