Adult wilms' tumor metastatic to the lung: endobronchial ultrasound-guided fine needle aspiration biopsy.

Adult Wilms' tumor (WT) is a rare entity with less than 300 cases reported to date in the medical literature. Histologic and cytologic features of adult WT of the kidney are similar to findings in pediatric WT. While the lungs are noted to be the most frequent site of metastatic disease in the pediatric population, the incidence of lung metastases remains unknown for adult WT. A search revealed 38 cases of adult WT with lung metastases published to date in the English literature. Amongst these cases only two have utilized cytology of the lung lesions as a means to arrive at a final diagnosis. We report a case of adult WT metastatic to the lung that was initially diagnosed using endobronchial ultrasound-guided fine needle aspiration biopsy. The aim is to compare the current cytologic and immunohistochemical findings with those cases previously published, to outline the cytologic features of adult WT metastatic to the lung, and to emphasize the significance of cytologic diagnosis in the work-up of adult WT.