RESUMEN
Wilms tumor (WT) is the commonest cause of renal cancer in children. In Europe, a diagnosis is made for most cases on typical clinical and radiological findings, prior to pre-operative chemotherapy. Here, we describe a case of a young boy presenting with a large abdominal tumor, associated with raised serum alpha-fetoprotein (AFP) levels at diagnosis. Given the atypical features present, a biopsy was taken, and histology was consistent with WT, showing triphasic WT, with epithelial, stromal, and blastemal elements present, and positive WT1 and CD56 immunohistochemical staining. During pre-operative chemotherapy, serial serum AFP measurements showed further increases, despite a radiological response, before a subsequent fall to normal following nephrectomy. The resection specimen was comprised of ~55% and ~45% stromal and epithelial elements, respectively, with no anaplasia, but immunohistochemistry using AFP staining revealed positive mucinous intestinal epithelium, consistent with the serum AFP observations. The lack of correlation between tumor response and serum AFP levels in this case highlights a more general clinical unmet need to identify WT-specific circulating tumor markers.