Metastatic metanephric adenoma in a child

Area of Science:

• Oncology
• Pediatric Pathology
• Nephrology

Background:

• Metanephric adenoma is a rare renal neoplasm typically affecting adults with an excellent prognosis.
• Metastasis is exceptionally rare, with only one previously reported case of atypical metanephric adenoma.
• This study investigates a case that challenges the established understanding of metanephric adenoma behavior.

Observation:

• A 7-year-old girl presented with a large (9.5 cm) typical metanephric adenoma in her left kidney.
• The tumor exhibited classic histologic features, including tubular and papillary structures with glomeruloid bodies and psammoma bodies.
• Despite lacking atypia and showing rare mitotic activity, metastases were found in para-aortic, hilar, and aortic bifurcation lymph nodes.

Findings:

• Histologic, immunohistochemical (EMA-, Keratin AE1-, Keratin CAM5.2+, Cytokeratin 7+), and genetic (normal diploid karyotype, disomy 7 & 17) analysis confirmed a typical metanephric adenoma.
• The presence of metastases in lymph nodes in a histologically typical case is a significant finding.
• This case demonstrates that typical metanephric adenoma can present with metastatic disease.

Implications:

• The findings suggest that typical metanephric adenoma may have a broader spectrum of behavior than previously recognized.
• This case underscores the importance of thorough staging and follow-up, even in tumors considered to have an excellent prognosis.
• Further research is needed to understand the mechanisms driving metastasis in typical metanephric adenoma and to refine risk stratification in pediatric oncology.