Botryoid Wilms tumor: a non-existent "entity" causing diagnostic and staging difficulties.

Area of Science:

• Pediatric Oncology
• Nephropathology
• Tumor Morphology

Background:

• Botryoid growth in Wilms tumors, characterized by a grape-like appearance into the renal pelvis, has been historically considered rare.
• Previous studies suggested an association with stromal histology and a favorable prognosis, but comprehensive data on frequency and subtype correlation were lacking.

Purpose of the Study:

• To determine the true frequency of botryoid growth in Wilms tumors.
• To investigate the association of botryoid growth with Wilms tumor subtypes and clinical stages.
• To clarify the prognostic significance of botryoid growth and its impact on tumor staging.

Main Methods:

• Analysis of Wilms tumors with botryoid growth from the International Society of Paediatric Oncology (SIOP) United Kingdom 2001 Trial (2001-2011).
• Review of published literature on botryoid Wilms tumors.
• Subclassification of tumors according to SIOP criteria and staging.

Main Results:

• Botryoid growth was observed in 77/739 patients (10.4%) and occurred across all Wilms tumor histological subtypes and stages.
• Six cases were incorrectly upstaged to stage II based solely on the presence of botryoid growth.
• Event-free survival was 90% and overall survival was 96%.

Conclusions:

• Botryoid growth is a frequent morphological pattern in Wilms tumors, not a distinct entity.
• The presence of botryoid growth does not alter the tumor's stage and should not be used as a criterion for stage II classification.
• Wilms tumors with botryoid growth should be classified based on their overall histological features, which dictate prognosis and treatment.