Microscopical synopsis

 intratumoral angiodysplasia
 concentric cuffing of entrapped tubules ("onion skinning")
 heterologous differentiation
 epithelial components

• inactive embryonal epithelium (identical morphologically to metanephric adenoma (MA)
• carcinomatous component distinct from these lesions but identical morphologically to papillary renal cell carcinoma (PRCC).

Prognosis

 metastases to the regional lymph nodes at the time of diagnosis (1/9) (#11257617#)

Differential diagnosis

 congenital mesoblastic nephroma (CMN) -> intratumoral angiodysplasia, concentric cuffing of entrapped tubules ("onion skinning"), and heterologous differentiation. (#11257617#)

References

 Arroyo MR, Green DM, Perlman EJ, Beckwith JB, Argani P. The spectrum of metanephric adenofibroma and related lesions: clinicopathologic study of 25 cases from the National Wilms Tumor Study Group Pathology Center. Am J Surg Pathol. 2001 Apr;25(4):433-44. PMID: #11257617#