Cytodifferentiation of a Wilms' tumor pulmonary metastasis: theoretic and clinical implications

Rhabdomyoblastic pulmonary lesions in a patient with Wilms tumor: choristomas or metastases?

New lesions that occur while patients are receiving treatment for malignant tumors may represent not only difficulties in arriving at the correct diagnosis, but also impact on subsequent therapeutic options. We encountered a patient developing new pulmonary lesions during and after receiving treatment for Stage II Wilms tumor (WT). The presence of mature rhabdomyoblasts in multiple biopsy specimens allowed rational decisions to be made regarding subsequent therapy. This and other published experiences suggest that patients with WT may develop choristomas or have tumors, which undergo cytodifferentiation. Methodologies are now available allowing differentiation of these two processes.

Responsiveness of chemotherapy based on the histological type and Wilms' tumor suppressor gene mutation in bilateral Wilms' tumor

To clarify a characteristic of bilateral Wilms' tumor (WT), we examined the clinical and histological features, chemotherapy response and mutations in Wilms' tumor suppressor gene (WT1) in five patients. Deoxyribonucleic acid was extracted from peripheral lymphocytes and tumor samples, and direct DNA sequencing was performed to detect WT1 mutations. Paraffin sections were stained with H&E for histological review and immunostained with anti-WT1, anti-Ki-67, anti-S-100 protein and antimyogenin antibodies. In contrast to the single case of epithelial-type WT, the other four cases were fetal rhabdomyomatous nephroblastoma (FRN) or contained a premature skeletal muscle component and appeared to be resistant to chemotherapy because there was no reduction in tumor volume. However, after chemotherapy, most of the tumor components changed into mature striated muscle cells, most of which immunostained almost completely negative for Ki-67. All four cases had the same point mutation of WT1. From our results, the histological findings correlated with WT1 mutations in bilateral WT. The tumor volume of FRN did not decrease in response to chemotherapy. It is possible to predict the chemotherapy response by examining bilateral WT for WT1 mutations and the histological characteristics of tumors.