PMC5994688_01
Abdominal magnetic resonance imaging.. A: T2-weighted image; B: diffusion-weighted image; C: early phase image; D: late phase image.. Abdominal magnetic resonance imaging showed a left retroperitoneal tumour, which was isointense compared to skeletal muscle on T1- and T2-weighted imaging and was slightly hyperintense on diffusion-emphasized imaging.. The tumour showed contrast enhancement, which was slight in the early phase and strong in the late phase.
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T2-weighted imaging and was slightly hyperintense on diffusion-weighted imaging (Fig. 1). The tumour showed contrast enhancement, which was slight in the early phase and strong in the late phase. Therefore, a rich, fibrous tissue tumour (i.e., desmoid-type fibromatosis, solitary fibrous tumours, or other malignant mesenchymal tumours) was suspected. The number of mitotic figures was less than 1 in 20 representative high-power fields.
Macroscopic findings.. Grossly, the tumour included firm, tan, or white masses. The cut surface was firm. The tumour involved the left ureter (yellow arrows).
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Additionally, it invaded the left internal iliac artery and muscularis of the bladder (Fig. 2).
Hematoxylin and eosin (HE) staining and immunostaining.. A: Histological findings. The tumour involved the left ureter (hematoxylin and eosin [HE] staining; 12.5x magnification).. B: Histological findings. The tumour cells invaded the muscular layer of the left ureter (HE staining; 100x magnification).. C: Hematoxylin and eosin (HE) staining. The desmoid-type fibromatosis was composed of long fascicles of spindle cells (HE staining; 40x magnification).. D: Immunostaining for beta-catenin showed nuclear expression in neoplastic cells (100x magnification).
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Histopathologically, the tumour comprised spindle-shaped fibroblast-like cells which infiltrated into the ureter lumen and surrounding soft tissues; however, atypical cells were not found in the tumour (Fig. 3A-C). Immunohistochemistry for beta-catenin showed nuclear expression in almost all tumour cells (Fig. 3D).