The cystic spaces are lined by flattened or low cuboidal epithelium. The septa usually contain small foci of blastema and abortive tubules. There is no anaplasia. Tumors with larger expansile solid nodules that distort the septa are incompatible with the diagnosis of cystic partially differentiated nephroblastoma and should be treated like conventional nephroblastoma. Image courtesy of Dr. Jean-Christophe Fournet, Paris, France; humpath.com; Used with permission.