Abdomen / Pelvis for Thursday, June 4th, 2026

Contributed by Nemours Children's Hospital Orlando
Gleidson Silva, and George Koberlein .

History

  • 11-year-old female presenting initially with 1 week history of incontinence treated for a UTI, returning to the emergency department with abdominal distension, abdominopelvic pain, irregular menses and hypertension.

  • Laboratory analysis significant for a normal RBC and WBC, an unremarkable CMP, markedly elevated LDH, and the serum levels of HCG and AFP were within normal limits.

  • Initial imaging performed outside concerning for malignancy, transferred to a pediatric institution for further workup and management.

Images (Click any image to enlarge)

Axial post contrast CT
Axial post contrast CT
Axial post contrast CT
Coronal post contrast CT
Coronal MIP CT
Axial T2w MRI
Coronal T2w MRI
Axial T2w MRI
Saggital T2w MRI
Axial T2w MRI
Coronal T2w MRI

Question

What is your final diagnosis?

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Correct answer

Extra renal Wilms tumor

Discussion

Extra-renal Wilms tumor

  • Extra-renal Wilms tumor (ERWT) is a rare entity, accounting for <1% of Wilms tumors, with involvement of the female genital tract being exceptionally uncommon. Uterine primary ERWT is particularly rare in pediatric patients and poses a diagnostic challenge owing to its nonspecific clinical, imaging, and histopathologic features.

  • In this case, cross‑sectional imaging demonstrated a large pelvic mass arising from the uterus, without renal involvement, supporting an extrarenal primary tumor. CT revealed a heterogeneously enhancing uterine mass with areas of necrosis, associated with ascites, peritoneal implants, hepatic metastases, and pulmonary metastases, indicating advanced disease at presentation. MRI showed heterogeneous T2 signal intensity with diffuse diffusion restriction, consistent with a highly cellular malignant neoplasm. The absence of renal involvement is a critical imaging feature required to establish the diagnosis of ERWT.

  • Histopathologic examination demonstrated a primitive malignant neoplasm with glandular, tubular, and solid architecture, including focal glomeruloid features, raising consideration of Wilms tumor. Immunohistochemistry supported a Müllerian‑type epithelial phenotype with positivity for PAX8 and cytokeratins, retained INI‑1, and negative germ cell tumor markers. However, the absence of definitive nephrogenic differentiation and negative WT1 staining in tumor epithelium, with only patchy stromal positivity, are atypical for classic Wilms tumor and highlight the diagnostic complexity of extrarenal and so‑called adult‑type Wilms tumors.

  • Recent studies suggest that many gynecologic tumors historically classified as adult‑type or extrarenal Wilms tumors may represent a heterogeneous group of Müllerian‑derived or sarcomatous neoplasms, including DICER1‑associated tumors, with reported molecular alterations involving TP53, chromosome 11p loss of heterozygosity, and BRAF. These findings underscore the overlap between ERWT and other high‑grade pelvic malignancies.

  • From a radiologic standpoint, awareness of this rare diagnosis is important, as imaging plays a central role in confirming extrarenal origin, excluding renal involvement, defining disease extent, and guiding multidisciplinary management.

Differential diagnosis

Differential diagnosis

•Müllerian-derived malignancy

•Germ cell tumor

•Rhabdomyosarcoma or other pelvic sarcoma

•Metastatic renal Wilms tumor

References

  • 1. Servaes SE, Hoffer FA, Smith EA, Khanna G. Imaging of Wilms tumor: an update. Pediatr Radiol. 2019 Oct;49(11):1441-1452. doi: 10.1007/s00247-019-04423-3. Epub 2019 Oct 16. PMID: 31620845. 2. Thakkar NC, Sarin YK. Extra-Renal Wilms' Tumor: A Rare Diagnosis. APSP J Case Rep. 2015 May 1;6(2):17. PMID: 26064807; PMCID: PMC4448100. 3. Debertin JG, Hull NC, Dean Potter D Jr, Allen-Rhoades WA, Laack NN, Polites SF. Retroperitoneal extrarenal Wilms tumor: A diagnostic challenge and kidney-sparing approach. Radiol Case Rep. 2025 Sep 8;20(12):5866-5870. doi: 10.1016/j.radcr.2025.08.025. PMID: 40989056; PMCID: PMC12450630. 4. Thakkar NC, Sarin YK. Extra-renal Wilms’ tumor: a rare diagnosis. APSP J Case Rep. 2015;6:17. 5. Rojas Y, Slater BJ, Braverman RM, Eldin KW, Thompson PA, Wesson DE, Nuchtern JG. Extrarenal Wilms tumor: a case report and review of the literature. J Pediatr Surg. 2013 Jun;48(6):E33-5. doi: 10.1016/j.jpedsurg.2013.04.021. PMID: 23845655. 6. Maeda T, Tateishi U, Hasegawa T, Fujimoto H, Arai Y, Sugimura K. MRI of primary prostatic Wilms' tumor in a young adult. AJR Am J Roentgenol. 2006 Oct;187(4):W415-7. doi: 10.2214/AJR.05.0507. PMID: 16985114.