PMC7186576_01
Unenhanced and contrast-enhanced CT a) Unenhanced CT showed a heterogeneous mass behind the bladder. Small calcification was noted. The border between the tumour and the bladder was unclear. b) Contrast-enhanced CT demonstrated multilocular cysts and enhanced solid portions.
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On contrast-enhanced CT, the cyst walls and septa were enhanced (Fig. 1). A part of the septa or solid portion had tiny calcification (Fig. 1a).
MRI a) Most of the mass showed heterogeneous hypointensity on T1-weighted MR images (repetition time [TR]/effective echo time [TE], 450/6.5 ms), whereas some parts showed hyperintensity. b) T2-weighted images with fat-saturation showed a heterogeneous hyperintense mass with multiple septations (TR/TE, 4517/85 ms). c) Diffusion-weighted images showed slightly high intensity (TR/TE, 8000/82 ms, b-value = 1000s/mm2). d) On the coronal T2-weighted image, the tumour was located above the prostate and protruded into the bladder (TR/TE, 2000/121 ms).
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T2-weighted images, respectively (Fig. 2a and b). The high signal intensity area on T1-weighted images suggested a haemorrhagic change. The tumour showed a slightly high signal intensity on diffusion-weighted images (Fig. 2c). T2-weighted image, the tumour was located above the prostate and protruded into the bladder (Fig. 2d).
18F-FDG-PET. 18F-FDG-PET did not show abnormal uptake in the tumour.
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The tumour showed a positive embedded organ sign, suggesting the tumour originated from the prostate. 18F-FDG-PET did not show abnormal uptake in the tumour (Fig. 3). The systemic prostate biopsy revealed no malignant cells.
Pathologic findings a) Photograph of the cut surface of the prostate tumour showed a multilocular cystic mass. b) On the macrograph of the resected specimen, cysts were lined with a flattened luminal cell layer and some basal cells without nuclear atypia. The tumour stroma showed slight hypercellularity with scattered atypical spindle cells.
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Histologically, the tumour consisted of cystically dilated glandular structures and a slightly hypercellular stroma with scattered cytologically atypical spindle cells with enlarged nuclei (Fig. 4).