Cystic partially differentiated nephroblastoma

Cystic partially differentiated nephroblastomas are rare pediatric cystic renal tumors. They are distinct from pediatric nephromas although they have very similar imaging appearances.

Terminology

Evolving terminology regarding cystic nephromas and other cystic renal tumors reflects ongoing changes in classification, in step with shifting understanding of the disease processes and genetic aberrations.

Classically, cystic nephromas were thought to occur in a bimodal age distribution, affecting young children and adults in middle age and the generic term "multilocular cystic renal tumor" was sometimes used.

Lesions arising in children are distinct from adult cystic nephromas on both immunohistochemical and genetic bases, and are separately categorized by WHO

• cystic partially differentiated nephroblastoma (pediatric)
• pediatric cystic nephroma (pediatric)
• cystic nephroma (adult)

The remainder of this article will discuss the adult form of cystic partially differentiated nephroblastoma.

Epidemiology

Occurs in very young children (usually under 2 years old). Boys are more commonly affected than girls.

Pathology

Pathologically, these tumors are multilocular and exclusively cystic. In these respects, they are indistinguistable from pediatric cystic nephroma. However they contain nephroblastomatous tissue.

Septae include nephroblastomatous epithelial elements. There may be islands of undifferentiated blastema and differentiated mesenchymal elements. Septal elements may protrude into cystic spaces.

Radiology

These lesions are multicystic unilateral lesions. They are exclusively cystic with no expansile mass or solid component.

Differential diagnosis

• pediatric cystic nephroma
  • almost impossible to differentiate by imaging alone
  • DICER 1 mutation
  • older populate (under 5s rather than under 2s)
• cystic wilms tumor
  • truly cystic Wilms tumor is extremely rare and solid components that enhance would be likely