Fig. 27

Desmoplastic small round cell tumor in a 17-year-old male, who presented with urinary frequency and a palpable pelvic mass on digital rectal examination. a–c Axial CT images in the portal phase show confluent implants in the right subdiaphragmatic peritoneum with infiltration of Glisson’s capsule and liver parenchyma, as well as other peritoneal implants in the hepatic round ligament and mesentery (red arrows). d Axial pelvic CT scan shows a bulky solid mass in the rectovesical space (blue arrows). e Post-contrast fat-saturated axial T1-weighted MR image obtained after neoadjuvant chemotherapy allows a better depiction of the pelvic mass (blue arrows), which shows reduction in size compared to previous CT and heterogeneous uptake with infiltration of the adjacent seminal vesicles (yellow arrows). f Diffusion-weighted image (b = 800) shows significant restriction of the pelvic mass. g Intraoperative view after stripping of the right subdiaphragmatic peritoneum, demonstrating multiple implants in this location (red arrows) that were attached to the Glisson’s capsule. h Intraoperative view of the pelvis shows multiple implants with a dominant mass in the rectovesical space (blue arrows). i H&E stain photomicrograph of the pelvic mass shows cords and nests of undifferentiated small and round malignant cells, with numerous mitotic figures and single-cell necrosis, surrounded by a dense collagenous stroma