A case report of a rare retroperitoneal sarcoma in an adolescent

Figures

• 

  Fig. 1. Preoperative imaging assessment. (A) Coronal view of 3D Volume Rendering Technique (VRT) reconstructed from contrast-enhanced CT scans. It vividly illustrates the massive tumor (labeled as "Tumor") occupying a large portion of the left retroperitoneal space. The tumor causes significant inferior and lateral displacement of the left kidney (labeled as "Left Kidney"). The VRT image demonstrates the three-dimensional relationship and significant mass effect of the tumor on the lumbar spine and the abdominal aorta. (B) Axial T2-weighted Magnetic Resonance Imaging (MRI) scan. It reveals a large, well-defined, encapsulated tumor in the left retroperitoneum. The lesion demonstrates marked heterogeneous T2 signal intensity (mixed high and low signals). This appearance suggests extensive areas of necrosis, myxoid change, or cystic degeneration within the solid tumor components, consistent with the biological characteristics of a high-grade sarcoma. Significant downward displacement and compression of the left kidney by the tumor are evident.

• 

  Fig. 2. Histopathological and immunohistochemical characteristics of the retroperitoneal high-grade sarcoma. (A) Hematoxylin and eosin (H&E) staining (original magnification ×40) demonstrates a highly cellular neoplasm composed of densely packed spindle cells. (B) At higher magnification (H&E, original magnification ×100), the spindle cells are arranged in a classic "herringbone" architectural pattern within a collagen-rich stroma. The tumor cells exhibit marked cytologic atypia, characterized by enlarged nuclei, prominent nucleoli, and abundant lightly eosinophilic cytoplasm. (C–F) Representative immunohistochemical (IHC) staining (original magnification ×40 for all): (C) The tumor cells show only focal and weak positivity for Smooth Muscle Actin (SMA). (D) CD34 staining highlights the rich intratumorally vascular network, while the spindle cells remain negative. (E) The Ki-67 proliferation index is remarkably high (approximately 50%), indicating robust tumor proliferative activity. (F) The tumor cells exhibit diffuse and strong cytoplasmic positivity for Vimentin (Vim).

• 

  Fig. 3. Postoperative follow-up imaging assessment. (A) Postoperative axial non-contrast and contrast-enhanced CT scans. The images demonstrate postoperative changes in the left retroperitoneum. The white arrows indicate the absence of the left adrenal gland (resected en bloc with the tumor). The fat planes in the surgical bed are clear, with no evidence of abnormal soft tissue mass or local recurrence. (B) Postoperative coronal CT multiplanar reconstruction (MPR) images. The images visually demonstrate that the left kidney, which was previously severely displaced inferiorly by the massive tumor, has largely returned to its normal anatomical position. There are no enlarged lymph nodes around the retroperitoneal great vessels or signs of distant metastasis in the abdominal cavity.