Extrarenal Wilms' tumor can arise in a nephrogenic rest laying anywhere along the craniocaudal migration of the primitive mesonephros and metanephros.
Sites:
(1) retroperitoneum
(2) pelvic
(3) lumbosacral
(4) female genital organs (cervix, uterus, ovary, vagina)
(5) inguinal region
(6) paratesticular or vas deferens
(7) mediastinum or chest wall
Signs and symptoms:
(1) mass effect with compression
(2) pain
(3) weight loss
(4) site-specific (dyspnea, dysuria, vaginal bleeding, etc)
Pathologic features:
(1) triphasic pattern: epithelial, mesenchymal, blastemal
(2) variable presence of a teratoid component
Differential diagnosis:
(1) metastatic intrarenal Wilms' tumor
